Hi,

Here is my problem : I painted a small piece of resin with a coat of primer then a coat of black. Small areas needed white to be added. My white jar already contained thinner in it (tamiya acrylics). When applying the paint, the black coat underneath along with the primer transformed into a grayish sludge, leaving the resin exposed. What happened ? The black coat was totally dry when I tried to apply the white coat. Could it be the thinner (tamiya) that would be strong enough to dilute dried coats of paint ?

Thanks.

What have you thinned the white paint with? You have stated Tamiya but not which one of their thinners.

Tamiya thinner as well.

Sorry Tom what I meant was which of the Tamiya thinners you used. I believe there are 2 or 3 from memory.

I used X20A thinner.

so all of the paint layers were Tamiya acrylics and Tamiya acrylic thinner. I see no reason for there to have been any issues at all unless the primer and black had not adhered to the resin, but I would have thought if that was the case it should have lifted when the black was applied. Had the resin parts been washed prior to painting and so providing a grease free surface for the paint?

Yup ! I cleaned the part with dish soap prior to painting it; I really don't know why this happenned !

Sorry Tom I am at a complete loss then. All I can suggest is you apply these colours in the same order on some scrap plastic and see if the same issue occurs.

Two possibilities I can think of:

What was the type of primer used? Acrylic or Enamel?

Also, some resin parts use a strong release agent to get out of molds, and dish soap sometimes will not remove it. It some cases, depending on the manufacture, you will need to get a stronger cleaner, ie some companies sell a Resin prep cleaner that will cut through most release agents. I have used Sylvain Resin prep in the past, and it works great.

http://www.sylvanscalemodels.com/resinprep.htm

I used car primer; worked great with the first coat of paint (black) that I sprayed with my airbrush. It's when I decided to apply colour detailing (white and red, used straight from the paint jar with a bit of thinner) that the sludge appeared.