______________________________ Reply Separator _________________________________
Subject: Re: MGB Painting estimate.
Author: lawref@lawref.com (Ernest E. Gilbert) at BALT.SMTP
Date: 9/14/95 9:51 AM
>
> On stripping the old paint myself, he said sandblasting would warp the
>panels if I wasn't careful.
Absolutely correct on both points. Sand blasting can create local heating and
warp body panels.
I have had a different experience in sandblasting body panels. I use a
siphon type sandblaster, which generally means more air than sand. It keeps
the surface cool. The mechanism that causes the warping is not heat but the
peening of the surface with millions of tiny dents. This tends to stretch
the metal on that surface. When the one surface becomes "longer" than the
other side of the panel, the stresses can cause warping. If you only try to
remove the paint and not try to beat the living hell out of the surface, you
won't have any problem.
Blasting the floor panels can be a sleeper because they were covered with a
tar-like coating that won't blast off easily and even though they are not as
subject to warping you will create a lot of heat getting that stuff off.
Plain old scraper will be faster for the thick stuff. Incidentally, that's
the same problem blasting the old undercoating; sand just seems to bounce
off.
Sandblasting undercoating just isn't the way to remove it. Get yourself a
paint striping heat gun (Black & Decker, etc..). Use this and a scraper to
remove the undercoating. Apply heat to a small area to soften the
undercoating and using the putty knife remove it. Once you have some metal
exposed, apply the heat to the metal as close to the area to have its
undercoating removed. This will break the interface bond between the metal
and the undercoating, but allows the undercoating to be somewhat solid making
it come off in longer strips. After scraping off as much as you can, use
paint thinner or kerosene to desolve the remainder and whip clean. Before
painting, use a degreaser in this area to remove any oil based solvent
remaining (sandblasting won't do it, it just spreads it around). Now you are
ready to sandblast the floor pans.
Marty Schlining
57 MGA Coupe
75 MGB
I
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