Model Railroading > Polly scale paint cracking?

I just painted a locomotive with polly scale paint, Thinned it with rubbing alcohol, and when it started to dry it cracked? Is it an old batch of paint or should I have thinned it with something else?

Polly scale usualy holds up pretty well, I only thin it with that testors thinner for the polly scale im betting the alcohol made it crack.



Edited 1 time(s). Last edit at 10/14/09 16:25 by Afbombers.

I find anything other than filtered water makes it crack. I also find if it thinned just a little bit to much it cracks.

I never had it crack on me, but then I only thinned it with isopropyl alcohol just enough to for it to flow through the airbrush without clogging.

Ted Curphey
Ontario, OR

I just thin polly scale about 10-20% with tap water, or with an opened bottle of bottled water (non-carbonated, of course!). No cracking yet.

Cheers,
Harry

funnelfan Wrote:
-------------------------------------------------------
> I never had it crack on me, but then I only
> thinned it with isopropyl alcohol just enough to
> for it to flow through the airbrush without
> clogging.


Yeah ted, that's what I thinned it with! You showed me that.

Alcohol /can/ cause cracks, chips and flakes with most/all acrylic paints in most or all colors.

Or not!

Same for windshield washer fluid. Denatured alcohol seems (to me) to be less a problem with acrylics in general and a good thinner for craft acrylics.

Back in the early days of Polly S, Pactra and so forth it took the brute force of home chemistry to get a good finish. Times and paints have changed. Either do a test and let it cure a couple days to see what's going on or stick with water, manufacturer's recommended thinner or Golden (Liquitex) Airbrush Medium.

I have spoken directly with Floquil on this several times and they recommend Distilled water which can be bought for $2-3 dollars for a gallon at your local supermarket. They do not recommend tap water.

Bruce

I have over 10 years using Polly Scale and I just use tap water and I have never had any problems with cracking. Polly Scale says to use water and I followed that direction. If other things cause it to crack, then I am not going to try anything else.

Problem is that tap water varies greatly from place to place. What I had in Idaho was a lot more alkaline than what's piped into the house here in Oregon. Given the tiny amounts used in thinning acrylics, I use the mfr's thinner for consistency. Clean-up of the brush is OK with the others.

Interesting discussion. I've done up over 30 MRL locos using Polly Scale paint over the last five years. The bottle says, "To airbrush, thin with 4 parts paint to 1 part distilled water or Testors Universal Acrylic thinner No. 50496." Older jars are a bit different, "To airbrush, reduce 10-15% with distilled water." I've always just used tap water, straight out of the faucet. I have never experienced cracking paint. We do have a water softener installed in the house, does that make a difference?

I prefer Polly Scale Acrylic over anything else because of the ease of cleanup, more water! No acetone, no mineral spirits, just water. Good for the hands, good for the environment.

Mr. MRL