From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Clear coat paint is flaking off.
Date: 4 Jan 2001 03:19:49 GMT

Tom Thompson writes:


>> I have a metallic burgandy 2000 Bianchi Brava.  In several spots
>> the paint is scratched all the way down to the metal.  However, to
>> add insult to injury, the clear coat in the area surrounding the
>> scratch is bubbling and coming off.

> This is evidence of a defective clearcoat application

Not so.  Clear coats, as most automobile owners will find out, allow
ultra violet sunlight penetrate through the clear part to destroy the
whole layer instead of the surface that can be washed off.  The public
is so enamored with super glossy finishes that they fail to recognize
the cost.  This is old hat but most people don't recognize the that
dandruff they see on other cars is the future of their own expensive ride.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Clear coat paint is flaking off.
Date: 5 Jan 2001 02:39:58 GMT

Jay Beattie writes:

>>> This is evidence of a defective clearcoat application

>> Not so.  Clear coats, as most automobile owners will find out,
>> allow ultra violet sunlight penetrate through the clear part to
>> destroy the whole layer instead of the surface that can be washed
>> off.  The public is so enamored with super glossy finishes that
>> they fail to recognize the cost.  This is old hat but most people
>> don't recognize the that dandruff they see on other cars is the
>> future of their own expensive ride.

> PPG had a huge delamination problem a two-step enamel paint system
> used on Chryslers a number of years ago, IIRC.  Apparently the top
> color coat allowed the transmission of UV which oxidized the base
> coat. It is my understanding that modern top coats (including clear
> coats) are UV resistant and that Ditzler, PPG, BASF and others claim
> to have conquered the delamination problems caused by UV
> transmission.  I am not (much of) a painter and my recollection
> comes from reading the lawsuits against Chrysler.  Any way, the
> poster had problems with the top coat where the paint was already
> scratched or missing.  This sounds more like a localized problem and
> not rampant delamination caused by UV.

From observing relatively new cars on the road, this is still a large
problem.  Nearly all cars have clear coat today because the buyers
have no idea what it coasts and how fragile it is.  Most cars have a
silver base coat, regardless of color and get their color from a clear
coat that is not UV proof.  That's why scratching a paint job with a
sharp object always reveals the silver metallic undercoat and makes a
horrible scar.  Even white and black cars are painted this way to give
them pearlescence.

Jobst Brandt      <jbrandt@hpl.hp.com>