Subject: Re: Help: glass etching
From: dwilkins@parkrapids.cfa.org (Don Wilkins) 
Date: Aug 16 1995
Newsgroups: sci.chem

tmiller@Direct.CA (Tom Miller) wrote:

>Neil Blackmore <nblackmo@freenet.calgary.ab.ca> says:
>
>>Several years ago i was given a glass etching kit which used some sort of 
>>acid to frost the glass.  Doers anyone know what kind of acid this might 
>>have been and perhaps where i can get some?
>---------------------------------------------------
>Either hydrofluoric acid or fluosilicic acid.  Concentrated HF is available
>from any lab supply house - if you're not a chemist familiar with the 
>special toxicological properties and storage problems of HF, do yourself 
>a favour and buy a prediluted kit from a hobby shop.

Yes buy a kit but:

Do not even think about using concentrated HF. If you had the
background to know the hazards with conc. HF you wouldn't have needed
to ask the question.

Concentrated HF can give you the grand daddy of all chemical burns. It
also has a rather interesting property of behaving like a temporary
local anaesthetic (temporary only). Once the stuff gets a good hold it
stings like you wouldn't believe unless you had the experience before.
Most people get a HF burn only once in their career as a chemist. Once
is enough for most. Rubber gloves are a particular hazard because of
the local anaesthetic behavior. A small pinhole goes unnoticed until
it is too late.

The kits use ammonium bifluoride not diluted HF. This is an entirely
different beast but can still give burns contrary to the spiels of the
providers of the kits. 

I am a retired chemist with a fair amount of experience with HF and
frosting light bulbs. I was at a national craft show recently where a
sweet young thing promoting one of these products informed me in no
uncertain terms that their product (which contained NH4HF2) was not
acid. My suggestion that pH 2 was acidic went over her head. The
company incidentally did not know what an MSDS was and ran a demo
class for people off of the street with NO safety glasses.

Get the kit. Treat the stuff with a little respect and wash your hands
frequently even if you KNOW you didn't get any on them. 

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    dwilkins@parkrapids.polaristel.net          

From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: potassium dichromate (T.C.Hickstein)
Date: 12 Jan 1996 08:58:17 GMT

In article <4d4lp0$kq9@post.acadia.net>, puppetboy@acadia.net (Alexander
Elias) says:

>most hf that is sold to remove rust is called muriatic acid, and
>i think its pretty diluted; 5% or 15%, im not sure.

Muriatic acid is hydrochloric acid.

HF in any dilution is incredibly dangerous. Although I worked
in fluorine chemistry for years, I handle HF like it was a 
rattlesnake.

Jerry

Newsgroups: alt.engr.explosives,sci.chem
From: tam@quest1.questconsult.com (Timothy Melton)
Subject: Re: Consumer products with hydrofluoric acid?
Date: Tue, 8 Jul 1997 12:53:11 GMT

In article <5psfin$26s$1@gail.ripco.com>, David Richards <dr@ripco.com> wrote:

>More specifically, it leaches the calcium out. I've read reports of

Even more specifically, it reacts with the calcium to for CaF2.  NOT
something I want in my bones.

>experimenters being able to extract literally _pounds_ of calcium from an
>adult dog with a similar reaction. Not exactly a means of production
>suitable for industrial use, but interesting.... and painful.

VERY painful.  In fact HF burn victims cannot be given pain meds because
easing of the pain is an indicator of the progress of the treatment.  A
splash of anhydrous HF that covers 24 sq. inches of skin can kill you
simply by reacting with the Ca in your blood and inducing a cardiac arrest.
Allied Signal has plenty of info on HF.  It's nasty stuff.

Tim


--
Tim Melton                    tam@questconsult.com
Quest Consultants Inc.        http://www.questconsult.com/~tam
P.O. Box 721387               (405) 329-7475
Norman, Ok 73070-8069         Fax: (405) 329-7734