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Listers,
Craig Wright sent me this note describing his experiences
with various automotive finishes. I thought them worth
sharing.
I can add just one more. Two stage epoxy. This material is
usually used with fiber substrates for structural
materials. We all have used the two-part polymer to bond
stuff together, successfully if they were clean. It is very
strong, hardens like a rock, and is practically impervious
to anything. One natural state is clear.
In 1956 I was using a colored version of this material in a
rocket application. It was so tough you could paint it on
aluminum foil and crumple it after cure, and the finish
wouldn't crack.
A friend was painting his 1953 MG-TD and I talked him into
using it. I acquired it from our industrial supplier at a
reasonable cost, and got a painter to try it out. We used a
bright red with metallic gold particles, rather than
aluminum. Not flakes, you understand, but the size one uses
for a metallic finish. It was a bright red knock-out, and I
think the fender would dent without cracking the paint.
Lasted a long time. The painter wouldn't talk to us for 2
years because all his guns and nozzles were plugged with
cured epoxy. {9->
Steve
--
Steve Laifman < One first kiss, >
B9472289 < one first love, and >
< one first win, is all >
< you get in this life. >
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Date: Tue, 16 Feb 1999 14:01:26 -0800
From: Craig Wright <craig@p-d-g.com>
Organization: Product Design Group
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To: Steve Laifman <laifman@flash.net>
Subject: Re: painter
References: <C31D3EA7EC92D21189720000929B79583B508D@SJ-EXCHANGE>
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Steve,
I think that you are more right than wrong, which is the best
any of us can expect.
(I hope this isn't too long.)
I am not a professional painter but I have painted about 20 cars
during my 40 year hobby of restorations. My experience includes
lacquer, enamel, two part polyurethane, and two stage.
Lacquer - Hard, brittle paint that is applied in multiple thin
coats. It tacks in seconds and can be sanded in minutes. A good
lacquer job will be 15 to 20 coats with sanding between each
three or so. The final coat is sanded and then polished. This
can easily be done outside in your driveway. Since it dries fast
and is sanded, bugs and dust is not a problem. Mistakes can be
fixed before the next coats. Solid colors are easy and do not
require a clear coat, metallics are a bitch and work much better
with a clear coat. This allows you to sand and rub the clear to
achieve the gloss. In California, lacquer is still available for
the hobbyist and professional bona fide restoration shop.
Enamal/urethane - ( DuPont Centari) one part. Slow dry time,
requires a booth. Smooth glass finish is difficult. Orange peal
is rampant. Metallics are difficult to achieve uniform color.
2-3 coats is normal.
Urethane with hardener ( DuPont Centari)- Same as above except
it dries faster and can be color sanded in a couple of days. The
paint does not "skin" over, but hardens throughout the film.
This allow more success when color sanding. When painting
metallics it is important mist each coat to melt the coat and
allow the metal to flow out in order to achieve a uniform color.
Even so, you may find color variations between coats when color
sanding.
Two part Polyurethane - (Imron, Algrip sp?) This was originally
developed for airplanes and trucks. A very hard, quick dry, high
gloss paint. Usually 2-3 coats are applied. It tacks in 30 min.
and can be color sanded and polished the next day. Metallics
are still tough to achieve mirror surface finish due to sanding
through coats. Dust and bugs can be a problem for a class A
finish due to the 30 min. tack time, but airplanes, trucks and
boats are painted outside on calm days.
Two Stage - Base coat/Clear coat - (Dupont Croma) Great paint
for metallic colors. Both coats are two part chemistry, that is
they "harden" instead of "dry". The base coat is the color
metallic coat. It tacks in a min. or so and dries in 30-60 min.
It paints a lot like lacquer and goes on dull. 3-4 thin base
coats gives good coverage, is easy to paint and can be done in
your driveway since it tacks so fast. (It should be under a roof
to avoid bird/bug droppings.) The clear coat is applied
immediately following the base coat application, no sanding. 2-3
coats are used so that there is sufficient thickness for sanding
and polishing. You can sand with 600 after 2-3 coats and then
add 2 more coats. Final sanding is done wet, with 1200-1500
paper, checking your work with a small squeegee. If it is
applied in a paint both, by a skilled painter, in the right
environmental conditions, sanding is not necessary to achieve a
mirror like surface. The reality is that sanding and polishing
is usually required to remove some orange peal if you want a top
job. This is best left to the pros since it is easy to rub
through the clear, especially on the corners.
Touch-up - Solid color lacquer can be touched up in the middle
of a panel with good results. Using any other paint it will be
next to impossible to partially spray a panel without some haze
showing up around the perimeter of the patch. This is OK for a
truck or airplane, but usually no for our pride and joys.
Brief How-To:
There are three requirements to a good paint job; Lots of work,
quality materials and some skill.
The work and quality materials is what costs all of the money,
but most of the work you can do yourself. The most important
part of the job is preparation. Sand, sand, sand.
Once the bodywork is straight, the bare metal must be prepped
with an etch that removes the loose oxides and passivates the
the surface. This give you a couple of hours to apply the
primer. Apply a couple of coats of primer and then a mist coat
(very light) of black lacquer. This is called a guide coat. Then
wet block sand with 320 to 400 paper only until all of the black
is removed. Never use your bare hands. For large flat areas use
a hard rubber block and for curves use a flexible neoprene pad.
The guide coat left behead will highlight most flaws; scratches,
pinholes, waves etc. Then lather, rinse, repeat until a uniform
primer surface remains. Take car to painter and you will be
amazed at how much cheaper it is.
The base/coat clear/coat systems can be painted outside at home
with some practice. The final sand will remove runs, bug legs
(the bodies can be knocked of after the paint hardens), dust
flaws, and bug droppings. Bird droppings are a problem and would
require a re-coat of clear.
Steve Laifman wrote:
> info@bcmustang.com wrote:
>
> > you are wrong
>
> OK, BC
--
**********************************************************************
Craig Wright Product Design Group, Inc.
craig@p-d-g.com 4635 Viewridge Ave.
(619) 569-3484 x309 San Diego, CA 92123
fax: (619) 569-3490 http://www.p-d-g.com
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