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plastic 'grain' showing through paint

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  • Member since
    November 2005
plastic 'grain' showing through paint
Posted by Anonymous on Sunday, October 3, 2004 4:07 AM
hey ive just been doing some airbrushing and now tht the paint has dried and i have examined the parts i have noticed that the plastic grain(or like the patterns or swirls in the plastic) is showing thru the paint job....

now i was just wondering whats causing this? is my paint to thin? or do i need several coats of paint (already bout 3-4)? or is it cause i didnt rough the surface up with a scotch brite pad?

thanks for the help!!!
  • Member since
    August 2004
  • From: Kennesaw, GA
Posted by jdavidb on Sunday, October 3, 2004 4:22 AM
wow 3 or 4 coats already. What kind of paint is it? Are you brushing it on or airbrushing?

Some of the Testors MM car enamels are "semi transparent pearlescent" according to Testors site, but there is nothing on the labels telling which ones are semi and which ones are solid colors. I don't know if you're using one of those paints. Maybe you got a semi-transparent.
  • Member since
    November 2005
Posted by Anonymous on Sunday, October 3, 2004 6:33 AM
im using automotive paints, in semi gloss black..... its quite visible on some parts while other parts show no signs of it..... im guessing im not puting on enuf paint or that its to thin....
  • Member since
    November 2005
Posted by Anonymous on Sunday, October 3, 2004 6:52 AM
prime the parts before spraying. oughtta help. laying down a coat of primer almost garauntees a good paintjob, its just kinda troublesome.
  • Member since
    April 2003
  • From: NSW, Australia
Posted by pingtang on Sunday, October 3, 2004 6:59 AM
Is the grain scratches on the plastic or discolouration of the plastic. If it's scratches, you need to sand the surface with some finer grade sand paper until the scratches are less obvious. If it's discolouration, You'll need more coats.

Another problem could be the kind of paint you are using. Some auto paints can 'craze' the plastic. I tried a gloss black auto enamel on some plastic the other day and it dried really grainy and flat. Almost like it was trying to peel. I'd say this is more likely to be the problem. If you have a spare piece of plastic, make sure it is smooth and spray some of the paint on it. If it dries "grainy", then that is the problem.

Hope this helps.
-Daniel
  • Member since
    November 2005
Posted by Anonymous on Sunday, October 3, 2004 1:20 PM
fingerprints?

try painting a thin coat of silver first, then your translucent paint.
  • Member since
    November 2005
Posted by Anonymous on Sunday, October 3, 2004 7:37 PM
pingtang: i just noticed ur an ozzie... what kinda paint did u try? the one i got is motorspray sub frame black quick drying enamel.... im trying these autopaints coz i go thru a jar of tamiya paint in a heartbeat(my lhs only sells the mini jars!) with my ab (im just a beginner aswell...) and i use alot of semi gloss blk so i thouigh id give it a go....
i did try it on a kit laying around, but being the dumbass that i am, forgot that it was already coated in white paint.... so im not to sure if its ok for plastic..... ill give it a go on some 'bare' plastric 2nite....
  • Member since
    April 2003
  • From: NSW, Australia
Posted by pingtang on Monday, October 4, 2004 3:19 AM
I tried a cheap enamel from an auto shop. I needed a gloss black primer to use with alclad and I thought I'd give it a go. Tamiya spray can black (TS-29 I think) works good if you can get your hands on it. It doesn't run out quite as quickly as a little jar.
-Daniel
  • Member since
    November 2005
Posted by Anonymous on Monday, October 4, 2004 9:06 AM
hey i painted some of the paint on bare plastic this time, and it hasnt dries flat and grainy, but its not perfect... it has spots and fine lines in it, but im guessing this is from non prep'ed plastic amd dust. the paint finish was semi glosss, like it was meant to be. if the plastic was crazed i would be able to tell straight away right? coz i had to look closely at this and wasnt sure if it was a dodgy paint job or the paint attacking thee plastic....
pingtang : im in oz aswell ( iwasnt to clear in my last post plus it dont say under my name) so do u have a name of the paint so that i know to steer clear of it in the future?

cheers!
  • Member since
    November 2005
Posted by Anonymous on Monday, October 4, 2004 7:29 PM
if it's the paint not the plastic unerneeth, try micromesh sandpaper in those little squares that are like 40,000 grit
  • Member since
    November 2005
Posted by Anonymous on Wednesday, October 6, 2004 11:56 AM
hey guys....
i think im on to something here.... i sprayed the parts using 2 types of paint as primer... now both paints were grey automotive enamels(both the same brand), one being labeled a primer and the othe as a gloss... now i sprayed both and it looks as tho the gloss has crazed the plastic but the matt primer hasnt.... now ive used some other colours from this brand (matt aswell) and they didnt craze the plastic at all.... now is this possible? thata gloss will craze and a matt wont....??
  • Member since
    August 2004
  • From: Kennesaw, GA
Posted by jdavidb on Wednesday, October 6, 2004 2:04 PM
QUOTE: gloss will craze and a matt wont....??


It probably did attack the plastic, yet it is just not visible because of how matte absorbs light rather than reflect it. Plus, matte is better at filling in cavities. Matte probably did its own crazing, and filled in it in at the same time. Or, if you sprayed the matte on over the gloss, the matte is not likely to do more crazing. It will try to fill in the damage that the gloss did.
  • Member since
    November 2005
Posted by Anonymous on Wednesday, October 6, 2004 9:28 PM
oh and another thing i noticed, when i was handling the gloss parts they kinda felt real sticky, like the paint wasnt completley dry.... but the matt feels perfect..... damn i though i was onto something good with these paints!!
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