Page updated on 11-21-2017

A Question About Painting


Chakakhan
05-26-2012, 11:40 PM
So after a hiatus from modeling, I've picked it back up. My major gripe then - and now - is achieving a nice, smooth paint job on car bodies. The paint has a texture to it. It's hard to describe - it's like very small bumps, a very fine grain. I've tried a bunch of things. If I take my time and mist coat, wet coat etc., or if I get frustrated and just lay down a heavy coat right away on a piece of scrap, the texture is the same. I airbrush Tamiya acrylics. I've tried a bunch of different thinning ratios, from heavier on paint to thinning it to the point right before it runs, and the texture stays the same. I've tried sanding between coats - does nothing. I don't know if I'm being unrealistic about how smooth I can get it without clear coat or polish or if it's just my techniques. I've read a bunch of guides on it, but that texture still haunts me. What can I do? should I try lacquer perhaps?

Maybe I can get a picture of a random piece I painted to see if I could yield any different results. Guess how that turned out?

Oh, and while I'm at it, I should ask; what is a good clear coat for acrylics?

turbothirtytwo
05-27-2012, 01:17 AM
acrylics arent good type of paint for body, try lacquers they are more resistent to polishing. dont worry if there is a texture in your paint job, some good coat of clear and polishing will carry of it. I never manage to get surface without texture. super clear from gunze is great product BTW. try that and when you will use to maybe get a 2k automotive clear

sasmiha
05-27-2012, 08:58 AM
May be you want to try Levelling Thinner from Gunze, as I did and that gave a smooth finish and improve the texture considerably, my opinion.

HTH,
Harris

MPWR
05-27-2012, 09:14 AM
It is technique- and it is certainly better to fix your technique in spraying than it is to fix the errors in the paint after you've sprayed it (although doing both yields the best results).

The bumpy texture comes from the paint partially drying in the spray stream as you apply it. Tiny droplets of paint are changing state from liquid to semi-solid between the spray nozzle and the surface. When they strike the surface they stick, but because they are already semi solid and spherical in shape, they can't form a smooth layer- so they result in a texture.

The trick to avoiding a spray texture is not to allow the paint droplets the opportunity to semi-dry as you're spraying. There are three ways you can control it:

-Use more thinner. Making the paint wetter will make it harder to dry in stream. But this alone won't necessarily solve the issue, and you've apparently already experimented with it.

-Spray closer. Leaving less space between the spray nozzle and the surface you're painting will leave less time for the paint to dry. But there are of course practical limitations to how close you can spray. I usually spray at 2-3".

-Reduce your pressure. Just as you can blowdry hair using a blower with no heat, spraying with your compressor set at too high a pressure will dry the paint as you spray it. Reducing your spray pressure to the lowest pressure that will consistently spray paint will help a lot. I usually spray at 15-20 psi. If you can't adjust your pressure, you need to be able to. On most compressors, you can add a pressure regulator/water trap (http://www.amazon.com/Paasche-R-75-Regulator-Moisture-Trap/dp/B000BR2STI/ref=sr_1_3?ie=UTF8&qid=1338123613&sr=8-3) to do this job. They're not very expensive, and are absolutely necessary. This is what I would guess will be most helpful for you.

So for a rule of thumb to avoid spray texture, always spray with the lowest pressure you can use, with the paint thinned as wet as you can make it without pooling/running. You can control how readily the paint pools/runs by adjusting your spray distance as you spray, and by controlling the amount of paint you're releasing (dual action airbrushes).

The best texture free paint jobs usually come from dual action gravity fed airbrushes (http://www.amazon.com/Iwata-Medea-Revolution-Action-Large-Gravity/dp/B000BQS3UW/ref=sr_1_1?ie=UTF8&qid=1338124097&sr=8-1). Gravity feed requires less spray pressure to work than siphon feed (paint bottle below the airbrush). Often a good gravity feed brush will happily spray at 5psi or lower than what you would need to run a comparable siphon feed brush.

Hope this helps a bit.

ShadowBroker
05-27-2012, 01:37 PM
That bumps you are referring to is called orange peel, there is a guy called Entau that made a little tutorial on how to get a glass like finish, he doesn't focus as much on the painting, more on polishing, and i followed his tutorial with great results

go to this thread to see my results of polishing:
http://www.automotiveforums.com/vbulletin/showthread.php?t=1075835

and this one to see Entau's tutorial:

http://z12.invisionfree.com/ScaleModelsMalaysia/index.php?showtopic=5722

In my opinion paints don't matter that much if you are willing to polish out the imperfections, I only use tamiya colours and clears
Hope this helps :smokin:

ianc911
05-31-2012, 02:25 PM
MPWR is right that you will get the best result by having good spraying technique AND polishing, but it is MUCH less time-intensive to start with a fairly smooth finish first than have to sand and polish an orange-peely one.

Follow his advice on distance and pressure; if you're painting at 30-40 psi, you're asking for trouble. Stay close while spraying, and ensure you're adequately thinning the paint.

ianc

Add your comment to this topic!