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Chaulky paint- What did I do?

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  • Member since
    June 2009
Chaulky paint- What did I do?
Posted by jimbot58 on Thursday, December 2, 2010 3:16 AM

I seem to be having this recent problem-sometimes when spraying flat enamels(MM), I end up with a chaulky, dusty finish that will actually brush off with a cloth or brush. I considered myself experienced but I think part of the problem is with my eyesight. I don't see as well as I used to and it's hard to monitor what's going on at the surface, I don't see this happening until it's too late. I can't figure out if I'm too close/too far, pressure set too low/too high, too much/too little thinner or if I'm spraying on too much paint all at once. I never seemed to have this happen in the past!

Help with your advice/opinions!

 

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It's all about classic cars now!

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  • Member since
    August 2005
  • From: Sydney, Australia
Posted by Phil_H on Thursday, December 2, 2010 5:05 AM

Hi Jim,

This problem is more prevalent with acrylics, but it's not limited to acrylics.

It's often caused by spraying from too great a distance, at too high an air pressure, airbrushing insufficiently thinned paint,  airbrushing when the ambient temperature is too high or the humidity very low, or any combination of the above.

I would suggest airbrushing from about 4-6 inches from the subject, at about 20PSI or less and see how you go.

  • Member since
    September 2007
  • From: Truro Nova Scotia, Canada
Posted by SuppressionFire on Thursday, December 2, 2010 5:47 AM

Sounds like the paint is drying before its down.

Phil has the trouble shooting narrowed down. Do not adjust anything and just spray closer and possibly slower passes. Do this on scrap plastic or styrene stock.

If this does not cure the issue then start adjusting one thing at a time, next logical step would be to set the pressure lower.

This way you will pin point the problem and make notes of any adjustments for future reference to fine tune your system.

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  • Member since
    August 2006
  • From: Neenah, WI
Posted by HawkeyeHobbies on Thursday, December 2, 2010 8:08 AM

20psi or less? I'd say 15 or less. try mixing in some retarder. I usually stray from 3-6 inches from the surface.

Gerald "Hawkeye" Voigt

http://hawkeyes-squawkbox.com/

 

 

"Its not the workbench that makes the model, it is the modeler at the workbench."

  • Member since
    February 2003
  • From: A Spartan in the Wolverine State
Posted by rjkplasticmod on Thursday, December 2, 2010 8:56 AM

The paint is drying before it reaches the model.  Usually caused by thinning the paint too much &/or spraying from too great a distance.  For MM Enamels, I rarely thin more than 20% thinner unless I'm doing mottle at very close distance with very low psi.  For normal painting, I usually spray at 15-20psi from 4-6".

Regards,  Rick

RICK At My Age, I've Seen It All, Done It All, But I Don't Remember It All...
  • Member since
    March 2003
  • From: Illinois
Posted by wjbwjb29 on Thursday, December 2, 2010 12:24 PM

For a visual the paint should appear wet when you spray it on then dry quickly.

 

Bill

On the Bench:   Trumperter Tsesarevich on deck Glencoe USS Oregon

  • Member since
    August 2005
  • From: Sydney, Australia
Posted by Phil_H on Thursday, December 2, 2010 6:22 PM

HawkeyeHobbies

20psi or less? I'd say 15 or less. try mixing in some retarder. I usually stray from 3-6 inches from the surface.

Hi Gerald,

Not knowing what airbrush Jim is using, 20PSI  is a "safe" baseline value which should work with almost any airbrush. 15PSI may not be sufficient for some models, (eg. Badger 350, Paasche "H" or "VL")  as they may not draw paint (depending on how much it's been reduced) at that pressure. 

I'm not sure about retarders for enamels (Jim is using MM enamels). Gunze Mr Retarder? I believe I've read somewhere that naptha (lighter fluid) can be used as a retarder for enamels. (?)

  • Member since
    March 2003
  • From: Virginia
Posted by Wingman_kz on Friday, December 3, 2010 2:19 AM

There's an enamel retarder in the Floquil line. Still Testors. I've used it in nail polish and lacquers too. Not quite as effective with them but was just enough.

Another thing to watch for is a burr on the tip of your needle. Doesn't take much. Happened to me early this year. I kept getting a rough finish and didn't understand why. Was using paints and thinner I've used many times. I kept adjusting the mix and air and it didn't help. When I stopped for the day and cleaned the brush I noticed the tip of the needle dragged when I wiped it down. There was a very slight burr. I gave it a quick polish and tried again and everything was normal. I don't remember the needle hitting the trigger or anything when I used it last but it must have.

Just saying, that's something else to look for. It may just be lack of humidity.

Tony

            

  • Member since
    June 2009
Posted by jimbot58 on Saturday, December 4, 2010 2:02 AM

I thank you all for your input. I think that the most likely culprit may be me adding too much thinner! I seem to be over thinning for some reason. I haven't been real careful about thinning-just a dropper full of paint, another of thinner, mix it up and away I go! Getting lazy and impatient in my old age

*******

On my workbench now:

It's all about classic cars now!

Why can't I find the "Any" key on my keyboard?

 

 

 

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