Vanishing Top Coat Wierdness

Pianting Varnish Wierdness

I’m finally finishing the Kerr Stuart but I’ve hit a problem.

When I spray varnish onto the loco body the top coats of black paint seem to be disappearing to reveal the grey primer!

Anyone know what’s causing this and how to solve it?

Some information that may help you diagnose the problem. The body is from Shapeways, printed as Frosted Ultra Detail. I washed the body with a small amount of dilute detergent and rinsed it well. Spray painted undercoat (Humbrol acrylic primer), top coat of Humbrol Dirty Black acrylic (3 or 4 coats). Everything was looking good until I sprayed on two coats of varnish (Humbrol Matt for Acrylic) and then this happened.

Has anyone else seen this before and know how to solve the problem? All help much appreciated.


  1. Have you tried painting the black on top of the varnish and then applying another coat of varnish? Wonder if the previous coats did not seal properly causing the black paint to soak into the material?


    • Hi Steve, I don’t think you are seeing the primer under the paint. The top coat isn’t vanishing. What you are seeing is a bloom from the varnish drying in mid air before it hits the model. As fine particles dry and stick to the surface they reflect any light hitting them and appear almost white. The cause is either spraying from too far away or the varnish not being mixed thoroughly enough, so that the matting agent is more dense in some parts of the fluid than another. The simple solution is to shake the spray can really, really well and give it another coat so that it wets the surface. This should bring those loose particles back into a film of varnish and eliminate the bloom. I’ve had the same problem using an airbrush many years ago.


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