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From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 29 Feb 1996 02:00:30 GMT
In article <DnHxLu.FEC@bcstec.ca.boeing.com>, lajoie@eskimo.com says:
>Glass is not a solid, you know, it's a super-cooled liquid.
In this case, trust your senses, not what you have read or
think you have read. There might be an arguable point that
glass is something less than crystalline - though this
assertion is also probably incorrect - but there is absolutely
no doubt that glass is quite solid at ambient temperatures.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 2 Mar 1996 09:55:07 GMT
In article <DnMIys.2Dw@eskimo.com>, lajoie@eskimo.com (Stephen Lajoie) says:
>In article <4h31bu$ioo@geraldo.cc.utexas.edu>,
>Gerald L. Hurst <glhurst@onr.com> wrote:
>>In article <DnHxLu.FEC@bcstec.ca.boeing.com>, lajoie@eskimo.com says:
>>
>>>Glass is not a solid, you know, it's a super-cooled liquid.
>>
>>In this case, trust your senses, not what you have read or
>>think you have read. There might be an arguable point that
>>glass is something less than crystalline - though this
>>assertion is also probably incorrect - but there is absolutely
>>no doubt that glass is quite solid at ambient temperatures.
>>
>>Jerry (Ico)
>
>Charles Kittel , Intrduction to Solid State Physics , 5th ed. said:
> "A substance in the glassy state is a material formed by cooling from the
>normal liquid state and shows no discontinuous change such as
>crystallization at any temperature, but has become more rigid through a
>progressive increase in its viscosity. Any liquid or supercooled liquid
>whose shear viscosity is greater than about 10^13 poises (10^12 N s m^-2)
>is called a glass. This value is taken to define the liquid-glass
>transformation temperature T_g, and to define the boundary between the
>liquid state and the glassy state.
> Glasses, like ordinary liquids, possess atomic order only over a range
>of the order of one interatomic separation. "
>
>I don't think I need to recite Dr. Kittel's credentials on the subject. I
>would rather regard what he has written than your admonishment to ignore
>him.
That's great. Now that you have conceded that glass is not a liquid
you are just a step away from seeing that it qualifies as a solid.
Dr. Kittel is a little ambiguous in his second sentence, but then he
is a physicist, not a linguist. However, he redeems himself very
nicely by actually defining a numeric boundary between glasses and
liquids and establishing that they qualify as distinct states, as we
chemists have done for many years with our concept of "softening point."
I do not know if Dr. Kittel is the last authority on the actual viscosity
level which should be chosen as the borderline, but his principle is
certainly sound even if the location of his boundary is somewhat
arbitrary.
I don't believe any chemist (certainly not I) has ever argued that liquids
and glasses do not share the property of apparent disorder, except over
very short ranges. Personally, I do not believe that there is anything
in the way of a classical phase change in going from liquid to solid glass.
Kittel's boundary between the two "states" is simply an arbitrary line
drawn by him in the sand - even though it makes his theory more aligned
with my argument.
I see normal glass at room temperature as a solid, because it is a solid in
every classical and dictionary sense. When it is warmed it eventually
becomes a liquid in every classical sense. Inbetween it has inbetween
properties - it's a viscous liquid or a soft solid, take your pick. If,
like Dr. Kittel, you feel that you need a "softening point" or other
arbitrary boundary, pick one and call it "Kittel's softening point."
There are solids, liquids and gases in the workaday world. Some solids
have more pronounced crystal properties than others. Some show more
crystallinity when you stretch them. Some pass from detectable
crystallinity to apparent non crystallinity as you warm them, but they
do not melt. Crystallinity is not always an either-or proposition.
You know it when you see it, but you don't always see it when it's
there. Anyone who has played with "amorphous" sulfur or carbon
knows that those materials are the crystalline substances traveling
incognito.
But you don't have to be a chemist to tell a liquid from a solid. That
stuff inbetween answers well to the name "semisolid" and rarely lays
claim to a pedigree of crystallinity.
Why don't you see if you can dig up a famous solid state physicist who
actually states as you do that glass is not a solid at normal
temperatures. It is a giant leap from merely saying it is not crystalline
to depriving it of its status as a solid. Let's see some clear and SOLID
evidence. In a separate posting I have cited a reference to help you make your
case. It will lead you to an authority who, I am told, considered glass as
a viscous liquid. Perhaps he went so far as to deny that it was a solid
also. Mind you, you may run into an uncomfortable number of references
to the contrary.
Good luck.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 2 Mar 1996 09:03:03 GMT
In article <DnLsy4.7ry@bcstec.ca.boeing.com>, lajoie@eskimo.com says:
>You do know, I hope, that if it is not crystalline it is not
>"solid" in the solid state physics sense.
Solid state physics is not a holy cow.
>Glass = Amorphous material.
>Amorphous = no distinct crystalline structure.
>Solid = crystal structure.
>No crystalline structure means not solid.
Glass = Solid with limited range of order, i.e. microcrystalline.
Amorphous = not enough ordered range to give diffraction pattern.
Solid = Firm, coherent material which retains volume and shape.
No crystalline structure = no detectable or detected structure.
>That's part of my point. Glass flows, even the room temperature
>stuff that we use for windows flows. It moves very slowly, to be
>sure, but it still meets all the definitions of a liquid. No crystal
>structure, no phase change, no latent heat of fusion.
It so happens that ordinary glass does not flow at normal
temperatures, and most certainly not as compared with numerous
clearly "more crystalline" materials. Too many instruments
have depended on the superb elasticity of fused quartz and
glass for ultra accurate measurements. Yes, pure quartz is also
used in the form of a glass precisely because of its superb
resilience in such applications as micromicrobalances.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 2 Mar 1996 08:39:11 GMT
In article <DnLt8y.99x@bcstec.ca.boeing.com>, lajoie@eskimo.com says:
>In article <4h31bu$ioo@geraldo.cc.utexas.edu> glhurst@onr.com (Gerald L. Hurst) writes:
>>In article <DnHxLu.FEC@bcstec.ca.boeing.com>, lajoie@eskimo.com says:
>>>
>>
>>>Glass is not a solid, you know, it's a super-cooled liquid.
>>
>>In this case, trust your senses, not what you have read or
>>think you have read.
>
>!!! This speaks for itself.
Oh come now, don't play "scientificker than thou." An X-ray machine
looks at sample of glass, sees nothing at all, and has its computer
print out "liquid." A child looks at a marble and sees a material
"solid as a rock." The child sees more, thinks better and is right.
>>There might be an arguable point that
>>glass is something less than crystalline - though this
>>assertion is also probably incorrect - but there is absolutely
>>no doubt that glass is quite solid at ambient temperatures.
>>
>>Jerry (Ico)
>
>By definition, glass is not crystalline.
>
>I know. Glass appears solid. It's hard, it doesn't appear
>to flow over short periods of time, but you'll just have
>to get over it. Your senses are flat out wrong.
It appears solid (looks like a duck)
It's hard (quacks like a duck)
It doesn't flow (waddles like a duck)
Its a liquid (Fooled you, it's a camel)
OK, if one's senses aren't scientifickal enough, let us resort
to the last resort - shudder - a reference. Let's see, it would
appear that the definition of "glass" as a rigid liquid was the
brainchild of one G.W. Morey, probably in a work entitled
"The Properties of Glass" published I know not when, many years
ago by Reinhold. Unfortunately his opinion, although undoubtedly
acknowlwdged as, uhm interesting, was apparently not accepted by
even those who tip their hats to him in standard references before
going on to define glass as a SOLID.
Kingzett's Chemical Encyclodedia defines glass as:
A solid material without long range order in its structure.
It is isotropic, and gradually becomes liquid as the
temperature is raised, unlike a crystalline substance, which
melts sharply.
Van Nostrand's Scientific Encyclopedia seems to prefer the
definition of glass as:
...an inorganic product of fusion which has cooled to
a rigid solid without undergoing crystallization. It
is a solid.
The idea of glass as a "liquid" certainly has scientific urban
legend appeal if one likes to intellectualize concepts to the
always interesting reductio ad absurdum of some principle
hounded to its asymptotic demise. But if you rely on your
senses you'll probably come closer to a workable definition.
Find solace in the consoling thought that most crystals are
solids and most solids are crystalline if you look hard enough
and can settle for ordered domains of a few atoms - as in the case
of glass.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 3 Mar 1996 09:39:02 GMT
In article <DnoJv5.6v@eskimo.com>, lajoie@eskimo.com (Stephen Lajoie) says:
>Or you can look at page 90 of "Materials Science", 2nd ed, by
>Anderson, Leaver, Alexander and Rawlings:
>
>"Yet another situation arises in materials like glass in which order
>extends over distances embracing a few atoms only. This we call short
>range order and it is found also in liquids. Indeed, many solids which
>display short range order are actually supercooled liquids and are not
>strictly in equilibrium in this state. Glass will sometimes actually
>crystallize if given sufficient time (several hundred years) or if it is
>exposed to shock."
Read your own cite: Your author is right "... many SOLIDS ... are
actually supercooled liquids ...." He is absolutely correct, but as
the man says they are SOLIDS. Many solids are also actually crystal
lattices. Many solids are also cryptocrystalline. Many solids are
also amorphous. But ALL solids are also actually solids.
Your argument remains always the same. A material which is
obviously solid shares the amorphous character of liquids so
it cannot be what it obviously is by every classic definition.
When this debate began, every participant knew that amorphous solids
and liquids share the property of disorder. We do not need endless
references to tell us what we have always known as though repitition
will change the obvious facts.
We have had satisfactory definitions for the word "solid" for
centuries. Why do you think we created the phrases "amorphous
solid," "vitreous solid" and "glassy solid"?
All of your cites are drawn not from reference works attempting
to define words, but from technical treatises attempting to
link a specific chain of secondary properties. Their words
serve their limited purposes and as such are quite correct, but
they do not offer nor do they claim to offer a "definition."
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 3 Mar 1996 08:58:31 GMT
Once in a while you run into a fellow who is so confident of his own
genius that he sees all about him as "clueless." It is always a
pleasure to enter debate with such a a man or woman because you
can depend on them to get that neck stretched beyond the elastic
limit.
In article <Dno4wt.22r@eskimo.com>, lajoie@eskimo.com (Stephen Lajoie) says:
>Just because glass flows very slowly due to the very high viscosity of the
>supercooled liquid does not mean that it isn't flowing.
>
>That is my whole point, glass does not hold it's shape, though the
>diformaties may take many years to become obvious to the naked eye. Glass
>also very slowly crystalizes, becoming a true solid. For copmmon window
>glass, it is a slowly flowing liquid for hundreds of years.
Despite the fact that several posters have given you excellent reason
to believe that your database on this matter sucks, I would be the
last to remind you that the windows in old houses which have
relatively thick bases were installed that way and that glass objects
from ancient cultures in warm climates would be puddles now after
thousands of years.
--------------------------------[snip]
>Do you have a source? You keep saying that, but you do not offer any
>evidence that glass is satble over long periods of time. Do you really
>think that endless repetition will convince anyone? I've cited Kittel and
>Dickerson Gray and Haight. You have cited.....
>
>no one.
Shame, shame. You forgot to read my other post - the one time-stamped
1.5 hours before the one you are here replying to. To save you the
time, I will requote the relevant cites holding that glass is
a solid:
Kingzett's Chemical Encyclodedia defines glass as:
A solid material without long range order in its structure.
It is isotropic, and gradually becomes liquid as the
temperature is raised, unlike a crystalline substance, which
melts sharply.
Van Nostrand's Scientific Encyclopedia seems to prefer the
definition of glass as:
...an inorganic product of fusion which has cooled to
a rigid solid without undergoing crystallization. It
is a solid.
I would also call to your attention my rather lengthy posting under
this same thread regarding glass spiral gauges and their marvelous
elasticity and sensitivity. Does this fail to qualify as evidence
for the stability of glass as a rigid solid because I acquired
the knowledge through years of hands on experience with glass
vacuum systems instead of reading about it in a book?
------------------------------[snip my description of quartz glass]
>Which has nothing to do with the subject. Quartz is not a glass.
>It has a crystal structure, and is a true solid.
>
>You don't know the difference, I take it. Since you don't, further
>discussion is pointless.
If I understand you correctly, you are saying that there is no
point in further discussions with me because I am too stupid
to know that there is no such thing as quartz glass, i.e., vitreous
quartz, i.e., fuzed quartz, i.e., non-crystalline, transparent,
slow-softening silicon dioxide variously known by the four names
I just mentioned as well as by the trade name "Vitreosil."
Your blind spot lies in the fact that in quite properly recognizing
that glass has the structural properties of a very viscous
supercooled liquid you deny the fact that it is nontheless a SOLID.
Somehow you got the fiction in your head that a solid must be
"crystalline" to qualify as a solid. But solids qualify as such by
meeting the elementary criteria set out in every dictionary and
encyclopedia. Different solids have a variety of physical
characteristics, which may include an amorphous or noncrystalline
structure. If you deny solid status to glass on that basis then you
must do the same for amorphous natural quartz and amorphous carbon.
How many eons would have to pass to measure the flow or even the
crystallization of materials which survive geologic ages unchanged?
What was it you said in your recent dissertation on the "clueless"?
I am not beyond screwing up even simple physics problems
and have no excuse except carelessness brought on by my own
arrogance. If I am wrong, then I DESERVE to be hoisted by
my own petard. :-)
If you say so, who are we clueless to disagree :)
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 3 Mar 1996 09:50:20 GMT
In article <DnoJv5.6v@eskimo.com>, lajoie@eskimo.com (Stephen Lajoie) says:
>I have seen this flow myself in houses in Fresno, where the elevated
>temperatures greatly increased the flow of the glass. Summers in Fresno
>have long periods where the temperature exceeds 120 F.
You are the one who tossed his nose in the air at the suggestion
that one should trust his senses in identifying glass as a solid.
Your Fresno observations confirm the value of your mistrust.
If windows flow viscously under the slight head of a window pane,
then they must obey the other physical laws relating to viscous
fluids. Now, safety glass is so very highly stressed that you
can clearly see the colored lines with polarized lenses. Glass
has a very high tensile strength and those strain lines represent
a lot of force which could be relieved by an amount of flow far
too small to be noticeable. Tell us how it is that such glass
panels are able to maintain those high stresses over long
periods of time all over the planet whithout relaxing via viscous
flow. They do it in Fresno too.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 4 Mar 1996 08:20:51 GMT
In article <Dnpx75.IJC@eskimo.com>, lajoie@eskimo.com (Stephen Lajoie) says:
>Amorphous solid is often used to mean supercooled liquid.
"Amorphous solid" means what it says - solid without (crystalline)
form. When you react sucrose with sulfuric acid you get amorphous
carbon. Never having been a liquid, the carbon cannot qualify as
a "super-cooled liquid" but it is most certainly amorphous in the
widely accepted sense.
-----------[snip]
>A solid holds its shape. A liquid flows to the shape of its container.
>It turns out that the only thing that holds its shape is a crystal.
>Glass at room temperature has a very high viscosity near 10^19 Poise but
>it is still a Newtonian fluid.
I have a very ugly thought for you to ponder. 10^19 poise is a lot
of poise even in Texas. What if, in addition to these great gobs of
Newtonian viscosity, glass should happen to have just a relatively
teensy weensy bit of thyxotropy. Guess what? It wouldn't flow in
an eternity even in Freno window. That's right, given the thyxotropy
of a bucket of good oil well drilling mud, it would go nowhere.
I suppose it would follow that since thyxotropic liquids don't
flow, they aren't liquids.
>As my previous source pointed out, "amorphous solid" is an oxymoron.
The term has sufficed for countless chemistry texts and is widely
accepted. If you prefer, you may use the term "microcrystalline" but
please pick one or the other. I know that you have your ego entwined
with the concept of "supercooled liquid" but you need to learn that
that term is inadequate for two resons: 1) Not all amorphous
materials are products of a cooled liquid, and 2) The term is most
widely understood to refer to simple, stirrable liquids below their
equilibrium crystallization temperatures.
The term "amorphous solid" is oxymoronic only to the extent that it
contradicts your naive notion that a material may not be simultaneously
solid and have a limited range of crystalline order.
For you as a scientific dilettante it may seem very elegant to view
all non-crystalline solids as super cooled liquids but in real life
we would have to use a phrase like:
"super duper supercooled liquid that is so very, very
viscous that it has all the normal attributes of a solid
to the human senses - not to be confused with other
microcrystalline or so-called 'amorphous' solids which
are also microcrystalline but are not products of
supercooled liquids."
The terms "amorphous solid," and "vitreous solid" or simply "glassy
solid" do the job much better. That's why we use these phrases every
day in chemistry. Much contrary to your idea of our cluelessness,
we use them in full awareness of the nature and physical history of
these states of matter. Steve, you will someday have to come to
grips with the possibility that some who disagree with you may be
less clueless than yourself in some areas.
>Ah, if we have nothing to back up our opinions, and the truth is backed
>up by references and data, we simply discount the references and data and
>rely on our own common sense to reach our conclusions, NOT.
>
>I look forward to seeing references in your next post.
What do you mean "We"? Is that the royal pronoun or is it a strait
line looking for Tonto's classic answer? Do you really look forward
to my posting some references to support my assertion that ordinary
glasses are solids? "Forward" is probably the wrong direction since
I have already done so on two occasions, the second time in reply
to your last claim that I had not done so.
OK, I'll post them again here in hopes that they will become
discernable even to your calculated myopia:
Kingzett's Chemical Encyclodedia defines glass as:
A solid material without long range order in its structure.
It is isotropic, and gradually becomes liquid as the
temperature is raised, unlike a crystalline substance, which
melts sharply.
Van Nostrand's Scientific Encyclopedia seems to prefer the
definition of glass as:
...an inorganic product of fusion which has cooled to
a rigid solid without undergoing crystallization. It
is a solid.
Note the prominence of the word "solid" in these two standard
references. Also, the Merriam Webster Third International Dictionary
folks don't know that the word "amorphous" is oxymoronic in the
context of defining "glass." Perhaps you should straighten them
out.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 4 Mar 1996 21:29:33 GMT
In article <Dnqz07.Kzn@eskimo.com>, lajoie@eskimo.com (Stephen Lajoie) says:
>And you are confusing hardness with viscosity. By objective measurements,
>glass is harder than many true solids.
Now why would I do a fool thing like that? There is, however an
interesting relationship between the two. If you attempt to measure
the hardness of a high viscosity liquid with a diamond ball, you cannot
do so because the apparent hardness becomes a function of the time
of application of the pressure. Under the astronomical pressure of
that hard tip a solid genenerates a steady counterforce at a given
diameter whereas a liquid flows in such a manner as to produce a
counterforce which is a function of penetration velocity. Glass, under
these circumstances behaves like a typical solid, not yielding to the
pressure of the point until its hardness is exceeded regardless of the
rate of application of pressure. Thus it is that glassy materials may be
used for such applications as knife edges for balance beams.
>When I stick a solid in my x-ray camera, I can tell by the diffraction
>pattern it makes that it is a solid. A glass, on the other hand, looks
>like any other liquid.
No, you can merely differentiate some, but not all ordered materials
from those that have limited order as we understand that term.
In truth, we have great difficulty in recognizing order and often
assign to randomness patterns which are too subtle for us to see.
This is, however irrelevant to the present subject. For this
discussion it suffices that your x-ray machine tells us nothing
whatsoever about amorphous or liquid materials other than that it
"sees" nothing and thus has nothing to report.
>I've three books on solid state physics. Only Kittel even bothered to
>mention glass. All three discuss crystals tho', even Oxide crystals.
Of course. The authors are busy expanding the present paradigm of
contemporary physics and undoubtedly doing a good job of it. Glasses
are not nice, neat crystalline lattices with their mathematically
adaptable regularity. The authors do not fail to include glasses
because they do not belong to the universe of solids, but because
they do not readily lend themselves to the present paradigm's
methods. You yourself harumphed when someone mentioned wood as an
example of a solid. Your authors undoubtedly also do not include
wood in their studies of solids because it is, Uhhhh, too impure
and too "unfundamental" for contemporary solid state physics.
Nevertheless, wood and plastics and concrete and baseball hyde
leather are all solids.
>Not yet. The best I can do is find a few references that use "amorphous
>solid" interchangably with "supercooled liquid."
If that is the case, then perhaps you should expand your horizons to
any number of books on the more appropriate subject of chemistry,
where amorphous solids are an everyday reality which must be dealt
with on a practical scientific basis.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 5 Mar 1996 03:05:15 GMT
In article <DnrJsx.Bp6@midway.uchicago.edu>, meron@cars3.uchicago.edu says:
>What this whole debate illustrates is that we really don't have a
>good, clear cut, definition of a solid. Defining it as a single
>crystal is clear cut but very limiting while defining it as something
>that maintains its shape at pressures below some arbitrary X is just
>this, arbitrary.
In my opinion, which is precisely that, we do not need a "new"
definition of the indisputably arbitrary concept of "solid." if
the numerous existing definitions do not suit the precision of
expression required for a physical state of matter, we already
have other nouns and adjectives at our ready disposal to define
whatever mental picture we wish with adequate precision.
Unless we agree in advance on the meaning of a term by describing
it with adequate attention to details and limits, the question
"what is the definition of ...." is nothing more than a spitting
match between existing common usages. It is for this reason that
most common words have a multitude of dictionary definitions.
We scientists should probably best acknowledge the existing language
we learned as children is a wonderfully flexible medium suited for
a range of communications tasks, not all of which are or ought
to be scientific in nature.
We all know what a single crystal wire whisker is, at least in
general terms. It's solidity is not much in doubt. If we want to
make that silly second step and ask if a wire made of two crystals
is also solid, we had better take our question to a class on
philosophy.
Except for dropping the word "solid" from innumerable texts on
the subject of solid state physics, we could all live very
happily without ever using the word at all in our various sciences.
It would do little good though, if we merely immediately began
to squabble over the meaning of the term "rigid." :)
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 4 Mar 1996 22:23:30 GMT
In article <Dnr03J.B2z@bcstec.ca.boeing.com>, lajoie@eskimo.com says:
>> Now, safety glass is so very highly stressed that you
>>can clearly see the colored lines with polarized lenses. Glass
>>has a very high tensile strength and those strain lines represent
>>a lot of force which could be relieved by an amount of flow far
>>too small to be noticeable. Tell us how it is that such glass
>>panels are able to maintain those high stresses over long
>>periods of time all over the planet whithout relaxing via viscous
>>flow. They do it in Fresno too.
>
>I could tell you, but you don't believe my sources. I can tell
>that you don't know what safety glass is. Go look it up and you'll
>realize why you see the colored lines. HINT: It's not just glass!
Steven, if you go through life looking at the disagreement of others
as a sign of cluelessness, as you so obviously do, you will be right
most of the time except as to the location of that ignorance. You
are one rare individual to believe that there is a living adult so
clueless as to be unaware that much automotive safety glass is a
sandwich of glass and resin. However, your knowledge of this subject
is obviously as shallow as your comprehension of the nature,
abundance and uses of vitreous quartz.
Glass used in such applications as auto side windows, shower stalls,
french doors and the like is produced with a pattern of internal
strains such that on impact it readily shatters into a myriad
of dull fragments. So great is this pattern of strains that mere
vibration will sometimes result in catastrophic failure.
Investigate the aftermath of a housefire where the windows have been
blown out or knocked out by the fire department and you will find two
types of breakage - ordinary sharp window glass shards and small,
uniform dull-edged fragments of safety glass or so-called "tempered
glass" a true oxymoron if there ever was one.
The point is a simple one which you have yet to answer. How can
"tempered glass" maintain the great patterns of strain for
prolonged periods if it is subject to viscous flow which would
relieve any such stress by mere microscopic movement?
Unwanted strain is also present in glass objects which have not
been annealed properly at intermediate high temperatures. It is
such unrelieved strain which often accounts for exploding tumblers
or the sudden appearance of a crack in a favorite wine glass.
Rather than finding relief with time, these strains often wait
for years before producing a fracture under some modestly disturbing
influence such as a normally tolerable temperature fluctuation.
One last point. If you take a closer look at your resin-laminated
glass windshields, you will find that they are also made of
"tempered" glass." Did you really believe that the resin was
responsible for the complex breakage pattern and the dull fragments?
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 7 Mar 1996 11:34:29 GMT
In article <4hm0u1$3v9@agate.berkeley.edu>, doug@remarque.berkeley.edu
(Doug Merritt) says:
>Some interesting questions have been raised. One such is whether
>the definition "solid equals crystalline" is appropriate throughout
>the physical sciences, as opposed to being appropriate simply in
>some microdisciplines. (I was the one that claimed wood was a solid. :-)
If this is a serious question in your mind, I would like to ask
how broad your definition of the "physical sciences" is. Try to
convince yourself and a couple of PRACTICING chemists that pine is
a supercooled liquid and potmetal isn't a solid.
>Another interesting issue had to do with second order phase transitions;
>I'd have to read back to see who raised the question and what its essence
>was, but I do recall that no one answered it one way or the other.
No answer is necessary in the context of the argument. It has
been conceded that there is a transition between states as
stated by Kittel, but my argument holds that such a transition
is unecessary to establish the solidity of glass. I probably
doubt the validity of a transition at 10^13 poise more than those
who argue for the non-solid status of glass. Either way I would
not use it in the discussion if if it were USDA stamped.
>There were some other similarly probing issues that I personally felt
>were not addressed by *either* party of the central long running
>debate.
That's beautifully democratic of you. However, I have no obligation
to address any particular idea that gets thrown into the ring.
no matter how physically PC it may sound to the gallery. Frankly, I
think "second order phase transition" is nothing more than a buzz
phrase. I'd blow a razzberry if I knew the ascii.
I also find abhorrent the ROYAL IDEA that some "famous" solid state
physicist, by sheer force of prestige will someday proclaim that
ALL true solids are not only CRYSTALLINE but must have at least
six-fold rotational symmetry.
Wake up out there all you junior scientists! This is one hell of an
old planet and it is covered with all kinds of glasses. We've
been staring at them for thousands of years. If they were these
newtonian fluids that everyone keeps talking about, don't you
think we'd be inundated with evidence of flow, considering that
these self-same materials are commonly subjected to super intense
local pressure over prolonged periods as in Cinderellas spike heels
during a long ball.
If you want to think about it, why not. The beauty is that there
is absolutely no penalty for carefully weighing the evidence
for the next, say, ten years. Who knows, maybe in less time than
that, someone will come up with a quantum definition of glass
showing that it is impossible to determine the glassiness and
the solidity at the same time. Then you will be able to sally
forth and reach indecision in the context of a brand new
paradigm.
Personally, I think I'll throw a dart into the dictionary and
select a new word to see what quantum spin this forum can put on
it.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 7 Mar 1996 23:47:09 GMT
In article <lockyer.37.000B43B4@best.com>, lockyer@best.com (Thomas N.
Lockyer) says:
>John, in my practical experience, glass does flow. I built a vacation cabin
>in the Santa Cruz mountains and used recycled old windows. The glass is so
>drippy and streaked that you cannot see out, and the glass is thicker at the
>bottom of the panes. I have also heard of old church windows with the same
>problems. I must assume that glass is an amorphous solid with slow liguid
>flow characteristics at room temperature.
Could it possibly be that you installed the glass thick side down?
Tell us that you recognized that the glass would flow so you put
it in standing on the thin edge, and now the glass has flowed to
the bottom again. HAR, HAR :)
I guess they just don't make glass the way they used to. These days
you have to pay a premium for the striations - they call it
antique glass.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 10 Mar 1996 08:18:16 GMT
In article <4hu1hc$etp@guitar.ucr.edu>, baez@guitar.ucr.edu (john baez)
says:
>In article <4htpnc$763@geraldo.cc.utexas.edu> glhurst@onr.com (Gerald L.
>Hurst) writes:
>
>>Where did you read that a viscosity measurement had been made on
>>glass?
>
>Stephen Lajoie is the one who claims this has been done:
>
>In article <Dnx50H.J6L@bcstec.ca.boeing.com> lajoie@eskimo.com writes:
Huh? I had five references, 6 now, that says that glass is a
flowing super cooled liquid. I even cited one reference that
gave the viscosity of the glass, and one that said exactly
as I stated, that glass in a window flows.
Yes John, but LaJoie says they "gave" rather than "measured" the
viscosity of glass. Giving is often a less experimental proceture
than measuring.
Jerry (Ico)
-----
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 9 Mar 1996 01:39:48 GMT
In article <4hq7j9$dhc@guitar.ucr.edu>, baez@guitar.ucr.edu (john baez) says:
>In article <4hmhk5$ojh@geraldo.cc.utexas.edu> glhurst@onr.com (Gerald L.
>Hurst) writes:
>
>>Frankly, I
>>think "second order phase transition" is nothing more than a buzz
>>phrase. I'd blow a razzberry if I knew the ascii.
>
>Are you hinting that you don't know the definition of the term? If so,
>I'll be glad to explain it. Or are you suggesting that you aren't
>interested in its application to the present discussion?
I am suggesting that it is irrelevant to the discussion in the
context of the original proposition as stated by the proponent.
>True, whether glass exhibits a phase transition at low temperatures is
>not relevant to the question of whether Tom, Joe, or Harry want to call
>glass a "solid", a "supercooled liquid" or (how about this?) a "glass".
>But to me question of whether glass exhibits a phase transition at low
>temperatures (and the associated problem with studying systems that take
>an incredibly long time to equilibriate) is one of the more interesting
>aspects of this whole discussion, because it actually concerns physics.
>On the other hand, the question of what Tom, Joe, and Harry decide to
>call glass is about the most boring kind of question I can imagine.
>Wake me up when you guys agree. :-)
Your boredom is simply another affectation readily suited to your
patronizing attitude toward pragmatic science and those who practice
it.
If you'll lower your nose a few degrees, you may be able to
discern that central argument here deals first with the
question of whether glasses flow like super viscous fluids or
not. It may be of academic interest, even to me, whether there
is a discernible "phase transition" of some sort, which might
be detectable if one could run a differential thermal analysis
of unlimited sensitivity over unlimited time. However, the
existence or nonexistence of a thermal signature doesn't make
the tiniest bit of difference. Windows flow or windows do not
flow, that is the first question. If the fact is that they
do not flow then they are solid in every practical and time-
honored sense. If they do flow measurably and continuously,
then they are indeed supercooled superviscous liquids. This is
not my "definition" it is simply the current arbitrary rule
that the players have adopted.
I would be willing to bet that there are a great number of quite
intelligent physicists who ARE interested in the Tom, Joe and Harry
question of whether windows really flow, not to mention Thomas Edison,
Joseph Priestly and Harry Emeleus.
You have adopted an attitude of smug and over-pedantic superiority
in this discussion, turning a blind eye to evidence that should
be persuasive or at least strongly indicative of the truth of the
matter. That in itself is your right if it suits you, but you
can expect nothing but verbal brickbats from some of us who
do not take kindly to your non-contributory pissing from the
sidelines about the quality of the performance of the active
participants or the value of the resolution they seek.
John, you better get used to the fact that Tom, Joe and Harry may be
a darn sight more astute than you are in some areas. If you have no
interest in the discussion at hand why, don't you go haunt some
other discussion which is better atuned to your perpetual dance
on the fence of decision. Your strong suit does not seem to lie
in the area of interpreting and incorporating data from the real
world into existing paradigms..
I have noted that a second, more theoretical thread relating to
the concept of second order phase changes is well under way,
Why don't you go ahead and expound on that area. It is juicily
theoretical and sufficiently poorly defined to practically
guarantee that no mutually satisfactory answers will ever be
reached no matter how long the discussion goes on. It is in such
a discussion that you are most likely to find appreciation for
your relatively academic perspective on science.
You will note from my posts in other areas that I appreciate
your input and advice on many more esoteric matters such as
the relationship of the Boltzmann constant to the definition
of temperature. Given that your admirer, Doug Merritt, is on
an active flame campaign denouncing my unabashed criticism of your
sometimes patronizing attitude, why don't you just sit back
and let him avenge your besmirched honor.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 10 Mar 1996 06:45:21 GMT
In article <4ht8pq$e9a@guitar.ucr.edu>, baez@guitar.ucr.edu (john baez) says:
>In article <4hpooi$8qk@madeline.INS.CWRU.Edu> jjs17@po.cwru.edu writes:
>
>>Note it's meta-stable, so the "wait long enough"
>>doesn't apply - metastable (thermodynamic) states have an infinite
>>lifetime if there are no external energy sources. I think perhaps a
>>different term is needed...
>
>Oh, good, maybe you can answer some questions about this...
>
>How do folks show that certain systems out of equilibrium *never* get to
>equilibrium? I imagine this is a matter of theory rather than
>experiment (since an experiment can't differentiate between "never" and
>"not for a really long time"). I have no problem with theory! I'm just
>wondering what sort of techniques people use to show this sort of thing.
John, if you really want a good answer to your question, you need
to pose it to someone like Prigogine, who can offer some thermodynamic
insight.
However, on a simpler level, I seem to remember overhearing a
conversation by some smarter guys in which one of them said
that the distribution of energy in real atomic/molecular systems
may be bell shaped but there is a finite upper (quantum) limit.
As a simple 19th century chemist, I don't know if this is true
or not, but if it is, then it would appear that any so-called
metastable system in which the activation energy was higher than
that finite upper limit would be indefinitely stable in the absence
of additional energy input.
A conceivable example might be, say, diamond. The same kind of
reasoning that says all glasses must eventually crystallize
insists that diamonds are not really "forever"; they simply
take a very long time to turn into graphite. Is this a fact or
another scientific urban legend. You know, diamonds are for
the most part exceedingly old, yet many of them are flawless
despite the fact that the eye of the jewelers loupe can detect
a mighty small amount of black carbon. Heat that diamond up
to 1000 degC and you can produce a surface-only coat of black.
One thousand degrees is a lot of activation energy, and maybe it
is a fact that at room temperature a corresponding random jump
over that hill simply isn't in the quantum mechanical cards.
It seems unlikely that we could borrow the energy from
Heisenberg, either, because of the largish delta t involved.
If that is the case, then we might apply the same reasoning to
silica glass - after all it has a heck of a high softening point.
An asymptotic approach to "infinite" viscosity may be nothing
more than an idealized mathematical fiction of a continuous
energy spectrum for such systems.
Pardon my rambling speculation. I'm sure you know far more
about these esoteric QM matters than I do. Also, I should
reemphasize that my poor examples have nothing to do with the
marvelous theories of non-equilibrium thermodynamics that
others can tell us more about. I certainly hope they will,
because that field is truly exciting even if it is too
much for my gray head.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 9 Mar 1996 01:40:35 GMT
In article <Dnvns4.JC9@eskimo.com>, lajoie@eskimo.com (Stephen Lajoie) says:
>Someone else claimed to have listed all my references thus far. He got it
>wrong, as was all his other statements.
>
>My references, not including the X-ray diffraction book, were as follows:
>
>(1) Chemical Principles, 2nd ed. By Dickerson, Gray, and Haight. (This is
>the one that said that the glass in windows flows over time periods of 200
>years)
>
>(2) Introduction to Solid State Physics, 5th ed (the 6th didn't look that
>different, so I didn't buy it) by Kittel.
>
>(3) Materials Science, 2nd Ed, by Anderson, Leaver, Alexander, and Rawlings
>
>(4) Materials for Engineering, by Van Vlack.
>
>(5) Encyclopedia of Physics, 2nd ed, by Lerner and Trigg editors.
>
>I did forget the Webster's dictionary, which was quoted in half jest, to
>show that even Webster got it right.
>
>Also note that my encyclopedia was there, which Jerry forgot in
>his attack on me. If he's going to say I didn't quote one, he ought to be
>damn sure instead of speaking without knowing.
La Joie correct that I did not give him credit for quoting from
the Encyclopedia of Physics. Although I checked every available
post of La Joie's, I was unable to find the one in which he says he
listed this reference. Blame the newsreader :)
However, in the spirit of honesty and integrity which made this
nation great, I have spared no effort to right this wrong by
searching my entire personal physics library to find a copy
of that tome. Voila!, I found it, and I will now quote the
passage most aptly dealing with the question of whether glass
is or is not a solid from the chapter entitlte "Glass," p 442:
An amorphous, solid state can be achieved (1) by rapid
cooling of a viscous fluid ... The term "glass" is often
restricted to specify materials formed by process (1).
and
A glass is an elastically isotropic solid, characterized
by two independent elastic constants ..."
Nice material if you are looking for support for the idea that glass
is a solid. Are you sure this is the reference you quoted, Steve?
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 10 Mar 1996 23:33:38 GMT
In article <96031012343817965@engineers.com>, robert.macy@engineers.com
(Robert Macy) says:
>I still am confounded to explain *why* the windows in my home have
>changed dramatically in the last 25 years.
>
>We have "French door" paneling in an entrance we refer to as the "sun
>porch", over 120 little panes that have noticeably "bulged" out like
>someone blowing bubblegum.
>
>I know this is not a controlled experiement, and is only anecdotal, but
>it has happened.
>
>Now, why?
I don't know why, but it would be interesting to hear more details
about this "bulging" phenomenon. Are we talking about "ordinary"
window glass or is this some more unusual variant. It would be
possible in manufacture to anneal only one surface, which might
subject the glass to incredibly high strain and cause it to
flex like some bimetallic strip. I am only speculating, of course.
Please tell us more if there is more to tell.
This might be a good place to mention a most excellent book for anyone
interested in glass in general or in its alleged propensity to flow.
The book is called "Masterpieces of Glass" and contains about
150 plates of blown glass articles of great beauty from the Corning
museum and dating back to as long as 3500 years ago. Despite the fact
that the Egyptians et al were only able work low-melting glass as
compared with, say, renaissance to present day manufacturers, the
objects have perfect and undistorted form despite occasional
combinations of high mass and spindly support or a broad plate-like
expanse of glass on a central pillar.
Also of interest might be the magnificently crafted Clovis obsidian
arrowheads, which are razor sharp after some 12,000 years and are
more technically advanced than similar artifacts than 6th century
BC articles made of obsidian imported by the pre-pharoah Egyptians.
The latter articles are very numerous, reflecting the existence
of a well-known "obsidian exchange" commerce run by the Egyptians
over an incredibly large area of the earth. Obsidian is not native
to egypt.
As glasses go obsidian is acidic and relatively unstable, but, as far
as I can tell, the objects retain their original form exactly.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 9 Mar 1996 06:56:05 GMT
In article <4hqs06$ems@agate.berkeley.edu>, doug@remarque.berkeley.edu
(Doug Merritt) says:
>In article <4hqnh4$5jg@geraldo.cc.utexas.edu>,
>Gerald L. Hurst <glhurst@onr.com> wrote:
>>Given that your admirer, Doug Merritt, is on
>>an active flame campaign denouncing my unabashed criticism of your
>>sometimes patronizing attitude, why don't you just sit back
>>and let him avenge your besmirched honor.
>
>But Jerry, I admire you, too! ("Uh-oh", he says :-)
>
>However I think that you are completely misunderstanding what has
>been going on. I'll offer the interpretation that I've been making
>from the beginning:
>
>>In article <4hq7j9$dhc@guitar.ucr.edu>, baez@guitar.ucr.edu (john baez) says:
>>>
>>>In article <4hmhk5$ojh@geraldo.cc.utexas.edu> glhurst@onr.com (Gerald
>>>L. Hurst) writes:
>>>
>>>>think "second order phase transition" is nothing more than a buzz
>>>>phrase. I'd blow a razzberry if I knew the ascii.
>>>
>>>I'll be glad to explain it. Or are you suggesting that you aren't
>>>interested in its application to the present discussion?
>>>
>>I am suggesting that it is irrelevant to the discussion in the
>>context of the original proposition as stated by the proponent.
>
>This is the core of the misunderstanding. I was the first one to
>sneak in a reference to phase transitions. I was quickly corrected,
>in that there is no first order phase transition, but only a
>second order one. However,
Sorry to snip in mid treatise. Your article is worth reading,
and I suggest it be read by all. However, I'm afraid it is
you who are missing the point about the relevance of "secondary
phase transitions," i.e., phase changes not leading to crystallinity
but evidenced by some exothermic event.
Try this thought experiment:
You have a liquid which contains the pure cis-isomer of some
compound. You freeze the material to a glassy solid well
below the thermodynamic temperature at which the cis-isomer
is unstable with respect to the trans-isomer.
Now you insulate the sample perfectly and carefully measure any
exothermic phenomena over the next million years. You find
evidence of an exotherm, but the material does not appear
to crystallize. You conclude that a second order phase change
has occurred.
What is the significance of your finding to any argument
concerning the nature of the glass as a liquid or a solid?
Answer: None.
Substitute whatever non-crystalline structural changes you
wish for the cis- and trans- isomer example.
The point I made before in the form of a metaphoric razzberry
was simply that secondary phase change data would be merely
an indication of "change," with no necessary consequences for
considerations of the solid-liquid status of the glass.
You are very badly mistaken in taking the central theme as
some sort of "semantic" argument about the "meaning" of solid.
There is good reason to see the existence or non-existence
of measurable flow as a fundamental issue.
I will suggest but not insist that if we were to try to find
a universal definition of solid versus liquid, we might say that
a liquid is a materials which will take the form of a bounded
sphere in the absence of all but the non-gravitational interatomic
forces of its constituents. Please note that I am making a
suggestion, not pronouncement, strictly for conversational value.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 11 Mar 1996 08:16:14 GMT
In article <4hvs3c$d5l@pipe10.nyc.pipeline.com>, egreen@nyc.pipeline.com
(Edward Green) says:
>I am still uncertain about the sharpness of the experimental transition?
>Do we observe *anything* like a phase transition while cooling a melt below
>this temperature, or is it apparently a continuous transition?
>Experimentally difficult? And speaking of experiment... I still think
>there is an experimentally well defined phase transition observed at a
>lower temperature, which doesn't seem to be the topic of interest here,
>but may generate confusion.
Did someone whisper my name? Mea culpa, but not really. If I have been
somewhat cavalier in my dismissal of "secondary phase changes," I have
tried to limit it to THERMAL effects, not because such effects in slow
motion are devoid of all meaning, but because of the futility of trying
to measure that which cannot be measured in the thermal static of
real world imperfectly insulated calorimeters at least in the real
time sense.
Let me suggest that we look elsewhere for signs of some structural
change heralding a possible shift from mere high viscosity to the
true rigidity some suggest is the true hallmark of the "solid."
Allow me to point out that crystal phase changes are usually
accompanied by two phenomena, a thermal signature and a change in
density. Although the change may be to slow for conventional
calorimetry to track, that does not mean that both phenomena cannot
be measured. The density change offers easy access to accurate data
because it is cumululative. Allow ammonium nitrate in the 1.66
density state to stand around long enough on the unstable side of
its equilibrium temperature and, presto, a month later you have crystal
with a density of 1.72. You could never have detected a thing looking
for heat, yet there is the hard evidence of a phase change.
Let me also mention that you are now in a position to see the thermal
change by measuring the difference in the heat of solution of the two
phases. Run such a heat analysis every few hours and you wind up with
a trace showing an exothermic (or endothermic) signature.
Now, for comparison, let me quote from an old monograph (1927, 1965)
I own entitled appropriately "The Phases of Silica." There has
undoubtedly been more recent work, but here's a bird in the hand:
Even at room temperature glass is not completely quiescent.
Besides yielding to external stress, it undergoes spontaneous
structural change.
Ageing. Although apparently brought to a rigid and permanent
state by cooling to room temperature, vitreous silica (and
other glasses) can undergo a complex of internal changes
which betray themselves externally as changes in density,
dimensions and other properties.
Also
Glassmakers and glass scientists are convinced that whenever
the temperature of a glass is changed, its properties begin
to change and it approaches asymptotically a value that
represents some type of amorphous internal equilibrium
characteristic of this particular glass and its temperature.
The above also relates perhaps to the following quoted material so
I'm leaving the latter in.
>>But as far was what would happen in the limit of arbitrarily
>>slow cooling rates there are several scenarios
>>
>>(1) No transition, either equilibrium or dynamical
>>
>>(2) No equilibrium transition, but at some definite and finite
>>temperature there is a divergence of a relevant time-scale.
>>(This is a "dynamical transition".)
>>
>>(3) A dynamical transition at some finite temperature,
>>which coincides with an equilibrium transition.
>>(But perhaps tau varies as e^{e^{correlation length}} rather
>>than a power law.)
>>
>>(4) A dynamical transition at some finite temperature,
>>which is followed by an equilibrium transition at a lower
>>temperature.
>I begin to get some flavor of the issues involved. If we get to a region
>where a characteristic 'time scale' is very long, maybe the idea of
>thermodynamic equilibrium becomes a little touchy? (2) is a very nice
>possibility, which neatly pares aways one aspect of a phase transition
>(analyticity of the free energy) from another commonly observed aspect...
>maybe it would be nice to call this *some* kind of "phase transition",
>just to avoid confusion? If it happens at a definite temperature, it
>waddles like a phase transition, though maybe it doesn't quack like one.
>A platypus?? :-) I wonder if real systems can be *quite* this subtle
>though. But this does seem to correspond to our intuition of a system
>that just sort of winds down and gums up as we lower the temperature.
One way to find out might be to prepare numerous glass samples and
and measure their heats of reaction with whatever standard at various
long intervals against control samples of geologically aged silica
or the like. There is already a difference of a couple of
kilocalories per mole between the crystalline and vitreous materials.
This technique in effect is like a movie made in time delay motion
and will produce a thermal signature curve. Who knows, perhaps it has
been done.
>>(II) Ordinary "glass" (as found in windows) is not the only
>>kind of glass around. There are many systems, particular among polymers,
>>for which there may not even be an equilibrium crystalline phase.
>>Nonetheless, these systems are agreed to be _solids_ at low temperature:
>>crystallinity has nothing to do with it.
>
>Oh, I agree. No arguments from me about what 'really' constitutes a
>solid.
You'll get no argument from me.
>Agreed. I was also thinking of diamond as a substance that could probably
>happily resist shear until after the sun winked out. But even strong
>chemical bonds will break at some finite rate under random thermal
>fluctuation?
Are you quite certain that random thermal fluctuations may not hit a
quantum barrier lower than the activation energy, i.e. a high-side
limit to the energy distribution bell curve?
As you know there is a lot of dicta in the literature regarding
whether glass is a "real solid" or a "supercooled liquid" with
the token chemist in the group favoring the former. Here for
your amusement is the opinion of the author of the monograph cited
above:
To the chemist with thermodynamic leanings a glass is only
a liquid of very high viscosity; a liquid and a glass of
identical composition are but two aspects of one and the
same phase. To the physicist, on the other hand, liquid and
glass are as diferent as any two materials can possibly be
for glass is one of the physicists most perfect solids.
I am going to stay with the physicist, and treat liquid and
glass, in the present volume, as distinct phases, though
expressly disclaiming any possibility of an equilibrium
between the two.
Elsewhere in the book the author identifies 5 separate phases of
amorphous silica, one of which is the liquid phase. The most
interesting amorphous phase is one made by fast neutron bombardment
of just about any kind of solid SiO2; it is less dense than
conventional quartz but is said to be about 2.6 percent denser than
ordinary vitreous silica.
Various indications of some form of order are found in glassy
silica, but none that can be fitted into our normal idea of
crystallinity as in the sense of producing a crisp x-ray pattern.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: Another Exploding Drinking Glass
Date: 11 Mar 1996 08:26:00 GMT
In article <mAZ+mLAPQ2QxEwYX@upthorpe.demon.co.uk>, Oz
<Oz@upthorpe.demon.co.uk> says:
>In article <quellen.244.001DA998@azstarnet.com>, Joe Quellen
><quellen@azstarnet.com> writes
>
>>I was sitting in that breakfast restaurant again today and another
>>drinking glass exploded apparently spontaneously. This time it was full
>>of ice water, and indoors. According to the workers there have been four
>>explosions, all of the same type of glass. The are about 6 inches tall,
>>tapers from about 3 inches at the top, no scalloping, with a thick
>>bottom. Strange.
>
>This is a well known problem with toughened glass. It is made by air
>chilling the surface of the glass as it cools.
This is true but in the case of tumblers any tempering would
probably be purely accidental. Shaped objects, particularly
glasses with irregular thickness need to be annealed because
of the uneven forces.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 9 Mar 1996 20:42:31 GMT
In article <4hsbud$nqs@pipe9.nyc.pipeline.com>, egreen@nyc.pipeline.com
(Edward Green) says:
>'baez@guitar.ucr.edu (john baez)' wrote:
>
>>>Yes, this has happened to me. I was going to do a bit of glass
>>>blowing, but the glass rods were so bent in the middle that I
>>>couldn't roll it properly.
>>
>>This is interesting, but... Once I had a piece of copper wire which I
>>had stood on end, and it sagged over. Does this mean copper is liquid
>>too?
>
>It means that the solid/liquid distinction is a convenient rule of thumb,
>having something to do with long range order and time scales, and that we
>find that real condensed phases don't always observe this distinction so
>nicely, but rather show a range of properties between, say, liquified
>methane, and a nearly perfect ionic crystal at nearly absolute zero.
>
>(e.g. glass -- little long range order, brittle, copper -- more long
>range order, malleable)
>
>Once we look at things this way, does it seem very important to sweat
>which side of the fence we are going to put some items down on? No doubt
>if we explored suitable temperature and pressure ranges we could blur the
>distinction between 'condensed' phases and gas also.
If you are a philosopher, that perspective is perfectly adequate
and erudite. If you are an engineer, you had better hope that
the condensed phase foundation of your skyscraper is one of those
substances the technical guys have certified as a "solid." Although,
the sages who warned against building your house on sand didn't say
"liquid," they had the right idea. Consider the question that if glass
flows in the windows houses of modest age, then how will it perform in
modern (or for that matter ancient) structural applications? For those
of you who hadn't noticed, we use glass for a lot more applications
than earrings.
Most of us prefer our thinking and our math to follow smooth
continuous curves that lend themselves to easy extrapolation
or reductio ad absurdum logic, but sometimes our lives depend
on manifestations of discontinuous functions.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: Another Exploding Drinking Glass
Date: 11 Mar 1996 18:19:58 GMT
In article <Nmks8UA5c$QxEwOJ@upthorpe.demon.co.uk>, Oz
<Oz@upthorpe.demon.co.uk> says:
>In article <4i0o2o$60v@geraldo.cc.utexas.edu>, "Gerald L. Hurst"
><glhurst@onr.com> writes
>
>>This is true but in the case of tumblers any tempering would
>>probably be purely accidental. Shaped objects, particularly
>>glasses with irregular thickness need to be annealed because
>>of the uneven forces.
>
>Not so. About the commonest glass in the UK (and probably Europe) is
>made by Duralex and is toughened. It is heavily scalloped.
>
>They explode delightfully for no apparent reason on occasion. They are
>however very tough. I have dropped them onto flagstones on several
>occasions. If you catch them on the rebound before they bounce too
>often, they are OK.
Thank you for the most interesting information. I had read
many years ago about such properties of glasses with toughened
skins, but was completely unaware that they had actually made
the grade into production. Considering the problems we've
always had with flat glass, which has a more suitable
geometry than a glass with an extra thick bottom, I find the
actual satisfactory manufacture to be quite a technical achievement.
I am particularly impressed that these articles have such thick
bottoms as desfribed by the original poster, having always
assumed that such units, if they did come into commerce, would
be relatively thin and uniform.
Incidently, the reference I remember was at least 20 years ago
and was, I believe in one of the popular mags such as Mechanix
Illustrated or the like. They described a hypothetical, but
somewhat speculative scenario of dropping a tumbler from the
Empire State building and watching it bounce :)
If you have any more information, I would be very much interested
in hearing it. Thanks.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 10 Mar 1996 05:35:40 GMT
In article <4ht8cr$e81@guitar.ucr.edu>, baez@guitar.ucr.edu (john baez) says:
>I'm glad, though, that you're referring to the question of whether glass
>flows --- a physical property --- rather than the question of whether
>glass is "solid" --- a matter of definition!
John, you are getting close to understanding the nature of the
argument. One more little step and you will see that, strictly
for purposes of the present discussion, the absence of measurable
flow will suffice for a tentative definition of "solid."
If, on the other hand, it can be shown that glass really does
flow measurably, as in sagging windows, we may equally tentatively
conclude that, for purposes of the present discussion, glass is
not "solid," but is, in fact, a very viscous liquid.
There is more to come on the subject, either way but especially
if we arrive at the TENTATIVE conclusion that it is solid. There
is, however little reason to proceed to second until we have tagged
first.
Where did you read that a viscosity measurement had been made on
glass? You probably mean that someone SUGGESTED a value. If we knew
answer to the viscosity question we would know the answer to
the question of tentative solidity as defined hereinabove and
elsewhere ad nauseum.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 10 Mar 1996 05:59:14 GMT
In article <4ht6n0$e6n@guitar.ucr.edu>, baez@guitar.ucr.edu (john baez) says:
>In article <4hogk1$f39@geraldo.cc.utexas.edu> glhurst@onr.com (Gerald L.
>Hurst) writes:
>
>>In article <4hn5v9$cph@guitar.ucr.edu>, baez@guitar.ucr.edu (john baez) says:
>>
>>>Stop pretending to pass the "burden of proof" back and forth, folks.
>>
>>Golly John, it's nice of you to patronize us with your sage advice on
>>how to be a real scientist and the nature of the rules of allowable
>>discourse.
>
>Heh. I really annoy you, don't I?
Not as long as you stick to the non-technical stuff. Your comments
are usually brief and sufficiently content-free to serve as handy
bases for starting new themes or focusing old ones without actually
interfering with the flow of ideas. In this sense you provide a
valuable service which would be missed if you stopped.
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 13 Mar 1996 09:01:14 GMT
In article <4i2mk3$7vu@pipe9.nyc.pipeline.com>, egreen@nyc.pipeline.com
(Edward Green) says:
>(Gerald L. Hurst)' wrote:
>
>>> ... the solid/liquid distinction is a convenient rule of thumb,
>>>having something to do with long range order and time scales, and
>>>that we find that real condensed phases don't always observe this
>>>distinction so nicely, but rather show a range of properties between,
>>>say, liquified methane, and a nearly perfect ionic crystal at nearly
>>>absolute zero.
>>
>>If you are a philosopher, that perspective is perfectly adequate
>>and erudite. If you are an engineer, you had better hope that
>>the condensed phase foundation of your skyscraper is one of those
>>substances the technical guys have certified as a "solid."
>
>Oh dear. I seem to have run afoul of the practical scientist. And after
>all our pleasant discussion about tree sap! :-(
This is a forum largely dominated by academics if not by number
then by the size of the coat-tail retinue. There are sometimes
too many map-makers and too few scouts in this out-back medium
of the technical fringe. Considering the sheer number of participants
in sci.physics who have new theories of the universe, I'm surprised
that comments by an itenerant 19th century chemical scientifickal
regarding a tiny corner of materials science are not a welcome
relief. Of course, I realize that I am bending the rules by actually
suggesting the evaluation of observable data rather than the accepted
methods of pure thought. Alas it is my lot to be cursed with an
intellect so limited that I had to augment it with my hands.
The good news is that I am too stultified by years of trying to
hack out a living by applying what little science I know to
offer any significant degree of intellectual competition. The bad
news is that those years as a blue-collar scientist have left me
devoid of the finer sensibilities of the brighter lads and sometimes
both opinionated and outspoken as hell.
You ran afowl of nothing. You merely wandered out to left field
to pick some daisies and forgot what game was being played. We can
ruminate about philosophical aspects of the blurring of the
differences in vague definitions in a separate sub-thread if you
like, but strictly for the very limited purposes of the "flowing"
glass thread, we are not talking about anything more indefinite than
the simple concept of whether glasses are newtonian fluids. There
are a dozen different ways of phrasing this question in totally
different terms, but the question "does glass flow?" needs to
be answered even for those who insist that only diamond is solid. .
You have a right to invoke local Tibetan mantras or the book of
I Ching if you wish to, but I am sticking to an extremely
narrow thread. It was not my choice, but for the sake of trying
to settle at least one detail, I have taken the extreme and
difficultly defensible position that silica glass and its
common derivitives do NOT flow in the absence of substantial
external force or pressure. By the term "substantial," I have
suggested that we limit the force to non-gravitational inter-
atomic forces, which you can interpret as surface tension for an
object with macroscopic radii of curvature, if you wish. This
limitation is suggested only to prevent scenarios where a
solid "flows" under the pressure of a planet forming or a
hydraulic ram, which would also shove around crystal planes.
I have gone to great lengths elsewhere to give examples of other
"semi-solids" by descriptions of thyxotropic materials including
mud, simple gels and a theoretical structure for vitreous silica.
It is hardly necessary to tell me that these materials vary
all over the map in their degree of "solidity" and approach
to plain newtonian fluids. They come close, but they are distinct
because they DO have measureable physical discontinuities in
their response to distorting forces.
I am saying that glass does not flow. Liquids do flow. Even
viscous liquids flow. That is the criterion for the distinction,
strictly for purposes of this sub-thread discussion.
The beauty of this severe limitation is that you can prove that
I am wrong by simply showing that windows flow or that the
vitreous silica in the Canyon Diabolo meteorite crater flows
over geologic time or that a glass amphora from 1500 BC has flowed
or that obsidian arrowheads from 12,000 BC have flowed.
Or you can huff and puff with words of philosophical wisdom about
the frailty of human definitions until my house of glass melts.
>Shoot, man. If I want a skyscraper foundation, I want to know a *lot*
>more about it than that it is empirically 'solid'. I want to know a *lot*
>of hard facts about its properties, properties which would incidently
>serve to place it solidly in the 'solid' classification. Sheesh. The
>engineering is in the details.
You'll make a fine engineer. The definition is also in the details.
The normal structural parameters are as well known for glass as
they are for most materials of construction, but you will not
find any data on the sort of flow being discussed here for glass
or any other material. They measure the same parameters of tensile
strength, flexural strength, crush strength, shear strength, hardness,
impact strength, thermal expansion, thermal conductivity dielectric
constant and the like.
There are modest intensity tests for creep and cold-flow and such
which are routinely applied to weaker and much softer materials like
certain plastics. There you might more convincingly "blur" the
distinction between the flow of a liquid and low pressure plastic
flow - but resins are a world away from glass in properties
and usually far more detectably crystalline. Engineering tests
can only be applied to real phenomena, not properties extrapolated
by mathematicians to 21 zeroes.
>>Consider the question that if glass
>>flows in the windows houses of modest age, then how will it perform in
>>modern (or for that matter ancient) structural applications? For those
>>of you who hadn't noticed, we use glass for a lot more applications
>>than earrings.
>
>Did I express an opinion on this? I don't think so. My view, believe it
>or not, is probably a lot closer to yours than you might think. The
>answer to the "does glass flow" question is to find out some hard
>engineering facts about particular kinds of glass, not to argue about
>empirical classifications. Failing that, maybe we can make some *informed*
>empirical observation. My view of the question is hard headed engineer.
>Satisfied?
An opinion? No, merely an obfuscating generalization about the
futility, sigh, of bothering to analyze the available information.
I'm quite sure you are content to let glass into the family of
solids if the definition of such is fuzzy enough. I'm quite sure
also that you actually believe glass does not flow in our measurable
time scales. You have no convincing evidence to believe otherwise.
Any belief that glass does flow is based on speculation not
observation. Engineering data for flow such as is here being
discussed do not exist for any known material. All we have for
diamond or window panes is that nobody has measured or presumably
can measure any flow.
>>Most of us prefer our thinking and our math to follow smooth
>>continuous curves that lend themselves to easy extrapolation
>>or reductio ad absurdum logic, but sometimes our lives depend
>>on manifestations of discontinuous functions.
>
>I see... you seemed to think because I was arguing that the distinction
>liquid/solid can be blurred, and is somewhat conventional and arbitrary,
>that I was arguing "and therefore glass flows appreciably at room
>temperature in historical time scales." How would that follow? I don't
>follow my implied argument. :-)
I simply believe you were picking daisies. Any distinction can be
blurred if one wishes to do so. You're "that" would not follow,
and there is no "implied argument." Again, I do not believe that you
believe glass flows in historical times. At worst you are undecided
about whether glass might really simply have a "high" viscosity, but
you choose to express this doubt in terms "blurred definitions." I
suggest that it is not so much the intimations of slow flow as it is
the daisy pollen on the spectacles that is responsibe for the blur.
Jerry (Ico)
From: schumach@convex.com (Richard A. Schumacher)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 12 Mar 1996 20:17:02 -0600
>and erudite. If you are an engineer, you had better hope that
>the condensed phase foundation of your skyscraper is one of those
>substances the technical guys have certified as a "solid." Although,
Excellent example. The underground buildings of the SAC installation
at Cheyenne Mountain, WY are isolated on glass springs, precisely
because glass does not flow (plastically deform) at STP.
From: schumach@convex.com (Richard A. Schumacher)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 12 Mar 1996 20:14:13 -0600
>>John, in my practical experience, glass does flow. I built a vacation cabin
>>in the Santa Cruz mountains and used recycled old windows. The glass is so
>>drippy and streaked that you cannot see out, and the glass is thicker at the
>>bottom of the panes.
Back then, cheap glass was always drippy and streaky. And
it is easier to install a pane with the heavy end down. (Try
it.)
Glass does not flow at STP. It's a disordered _solid_, not
a liquid. They're different.
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 13 Mar 1996 23:48:25 GMT
In article <Do876G.4EL@midway.uchicago.edu>, meron@cars3.uchicago.edu says:
>>You have a right to invoke local Tibetan mantras or the book of
>>I Ching if you wish to, but I am sticking to an extremely
>>narrow thread.
>
>Well, I wish you luck. I tried to do it, more than once, usually with
>rather limited success.
I suppose in journal publications they call them "referees" because
they keep the mob from climbing into the ring. On UseNet, no matter
what the topic you can't hear the fat lady sing over the catcalls of
"Take it off."
Jerry (Ico)
From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: flowing glass
Date: 18 Mar 1996 07:40:55 GMT
In article <4ifpso$f5f@geraldo.cc.utexas.edu>, glhurst@onr.com (Gerald L.
Hurst) says:
There is a laboratory phenomenon called "zero creep" that
resembles viscous flow in glasses (4)."Zero creep" is not
a creep of zero magnitude but a creep of the 0°C calibration
temperatures on 0-400°C borosilicate (Pyrex) glass
thermometers. It may creep upward by as much as 1.4°C when
used intermittently for 20 years over its temperature range
and by 1.5°C in 210 h of heating at 410°C (5). The
thermometer bulb changes in size slowly. The explanation
illustrates more structural properties of glass.
>[Snip]
>In the present case, the author suggests that the 1.5 degree change
>in the calibration temperatures of borosilicate thermometers which
>occurs above 400 degrees represents an equilibrium phase change which
>agrees with the thermodynamically predicted value of 350 C. He
>suggests that material shifts into the supercooled liquid phase above
>ABOVE that T0g temperature, but is "infinitely" viscous below it.
As much as I like the author's argument insofar as it tends to
support the existence of a T0g phase change in glass as he says
is predicted by thermodynamic calculations, I must toss in a
caveat of my own.
At the peak operating temperature of the thermometer described, the
vapor pressure of mercury would be in the range of two atmospheres.
If I were designing such a thermometer, I would pressurize the
headspace to perhaps 20 atmospheres to prevent the boiling of
the fluid in case of severe overheating. If the instrument was so
designed, then one must consider the possibility that the change
in volume was merely reversible expansion under pressure analogous
to the temporary and eventually reversible deformation encountered
when glass tubing is stored with the ends overhanging the shelf.
Obviously, such deformation would be exacerbated by high
temperatures.
Sounds like the makings of some interesting additional experiments
with specially designed "thermometers."
Jerry (Ico)
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