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Rough finish airbrushing Model Master Acryl

#1 User is offline   ex-USMC_Hornet_WSO 

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Posted 03 January 2014 - 07:06 AM

So I just finished airbrushing Model Master Acryl flat paint and I ended up with an extremely rough finish. I know flat paint is supposed to have a rough surface at a microscopic level, but this is extremely rough with tiny but visible bumps that, if I press hard enough, I can brush off with my finger. I know it's not orange peel. Can anyone tell me what this is, how to fix it, and how to prevent it from happening? Thanks!

#2 User is offline   Kaibutsu 

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Posted 03 January 2014 - 07:12 AM

From what I have learned here, it sounds as though the paint is drying before it gets to the surface of the model.

Try spraying closer to the surface of the model.

#3 User is offline   Edgar 

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Posted 03 January 2014 - 07:14 AM

The usual reason is spraying too far away from the model for your ambient conditions, so that the paint is drying before it hits the model. Either spray from closer-in, spray at a lower room temperature, or add a retarder to your paint, to slow the drying time. It's a common phenomenon with acrylic paints, which why many stick to the slower-drying enamels.
Edgar

#4 User is offline   Jim S 

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Posted 03 January 2014 - 09:27 AM

All of the above are great ideas, all I can add is try lowering your air pressure too. You might have to thin the paint a little more to get it to flow. I usually use Tamiya thinner, with a little Liquitex retarder and start at like 15 PSI, seeing if it will flow. You can turn it up to like 18 PSI but don't go too far. The retarder is mixed with water. You could also try thinning with only distilled water, as the water does not evaporate as fast as thinner. Thinning with water also helps a tiny bit with the "dry tip" conundrum that occurs when spraying acrylics.

Hope this helps,

Jim S

This post has been edited by Jim S: 03 January 2014 - 10:03 AM


#5 User is offline   Pierre Sacha 

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Posted 03 January 2014 - 11:44 AM

Hi another tip that helps me a lot is to use the airbrush at its widest pattern or highest flow with a low pressure. You want the paint to go down shiny and wet-ish. A delicate balance just before it "spiders" or runs. Also be sure to spray close into the nooks and crannies or 90 degree angles such as the areas between the wing root and fuselage sides as these areas cause turbulence and an unwanted build up of that dreaded rough stuff.

Regards,

Pierre

#6 User is offline   Triarius 

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Posted 03 January 2014 - 06:41 PM

Drop your pressure and get closer. Thin to the consistency of 2% skim milk. Use a retarder or flow aid.

The pressure you use depends on your airbrush design. Siphon fed air brushes need higher operating pressures, gravity fed airbrushes lower. I generally airbrush in the 10 to 15 psi range with gravity fed, 15 to 18 for the siphon. If you need more pressure than that, you need to thin the paint more.

How do you know what the consistency of 2% skim milk is? Pour some milk into a glass. Swirl. Note how the milk looks as it returns to the bottom of the glass. Thin your paint in a shot glass, and look for the same appearance.

#7 User is offline   randypandy831 

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Posted 03 January 2014 - 08:58 PM

I never used retarder when using MM acrylics. over thinning can cause a rough surface as well.

#8 User is offline   ex-USMC_Hornet_WSO 

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Posted 03 January 2014 - 09:27 PM

Thanks for the great advice everyone! Any tips on how to fix it? I'm thinking of dry sanding with 600-2000 grit to smooth it out. How long do I have to wait before I can start sanding?

#9 User is offline   Triarius 

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Posted 03 January 2014 - 10:59 PM

Wait 24 hours. Wet sand. I'd start with 800 grit. If that isn't producing a smooth surface, then drop to 600. For a flat finish, you needn't go above 800 grit.

#10 User is offline   Netz 

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Posted 04 January 2014 - 02:07 AM

Before hitting it with sand paper, you might try a plain house hold paper towel, use it dry, it's usually abrasive enough to knock down any rough surfaces in the paint.
Curt

This post has been edited by Netz: 04 January 2014 - 02:07 AM


#11 User is offline   ex-USMC_Hornet_WSO 

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Posted 04 January 2014 - 06:14 AM

View PostTriarius, on 03 January 2014 - 10:59 PM, said:

Wait 24 hours. Wet sand. I'd start with 800 grit. If that isn't producing a smooth surface, then drop to 600. For a flat finish, you needn't go above 800 grit.

Wet sanded with 1000 grit (didn't have 800) and it worked like a charm! Thanks!

#12 User is offline   balls47 

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Posted 04 January 2014 - 10:35 PM

Try a different brand of paint. (As Mr. Obama -can't bring myself to call him President- says,) PERIOD!!!

#13 User is offline   ex-USMC_Hornet_WSO 

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Posted 04 January 2014 - 10:39 PM

View Postballs47, on 04 January 2014 - 10:35 PM, said:

Try a different brand of paint. (As Mr. Obama -can't bring myself to call him President- says,) PERIOD!!!

I'd like to but Tamaya doesn't offer FS standard paints and Gunze Mr Color is hard to get.

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