Water based acrylic on Resin wheels

[49thStateRT]

I have a resin wheel aftermarket set that I painted with AK 3rd Gen water based acrylic rubber black. I usually use Tamiya acrylics which I feel do not brush paint well. This went on much better. I had not primed the resin wheels. I let it dry 24 hours and then went to take them off their toothpicks and simply handling them caused the paint to rub off like a dry powder. It stayed in the treads, but all the smooth parts I was able to quite easily rub off with my fingers. Is this an known issue with water based acrylics on resin ? Did I need to prime with a strong non water based primer ? Any advice thanks. I will likely just air brush on Tamiya rubber black now but want to know if AK acrylic is the issue, using water based on resin in general, or lack of priming. Thanks

 

[urumomo]

resin in as cast 2-part or 3D print ?
Did you wash them prior to paint ?

 

[49thStateRT]

no, did not wash. They are 3-d printed wheels

 

[urumomo]

water base usually has low bond on polymers , but the " coming off like powder " makes it sound like too dry / thin of a coat -- it should be forming a film with at least itself , regardless of substrate delamination

 

[Jakko]

I always prime resin parts (whether hand-cast or 3D-printed), because I've found that paints don't usually adhere well to them.

 

[the Baron]

Prime the pieces.
As far as Tamiya's acrylics go, which are not water-based, but alcohol-based, I brush them by hand all the time. But I prime the piece, and I thin the paint with Tamiya's proprietary X-20A acrylic thinner. I never have any problems applying the paint by hand. That's on resin or white metal figures.