Hi,
I've been working on a 3D printed model kit. After priming, it was sprayed with a couple of coats of Tamiya TS-101 (base white) and then a couple of coats of TS-026 (gloss white), both rattle cans. I then left it for around 3-4 days to cure before applying the decals. So far, so good. I then sprayed a couple of coats of Vallejo polyurethane satin varnish (27.652) to protect the finished model. After leaving it to cure for a day or so, the satin finish looked good, but there were a couple of tiny dust spots I decided to sand away with a wet Micromesh sanding stick (probably 4000 grit or higher). Instead of just taking off the dust spot, a section of the varnish layer came away from the model. I figured I probably hadn't given the varnish enough time to cure, so left it 4 or so more days hoping it would be cured by that time. However, when I tried the same sanding process again I took off even more of the varnish - in the end I was able to peel off pretty much the whole of the polyurethane coating!
So I'm back to having a painted and decaled, but unvarnished model, and I'm trying to decide on how I am going to apply the satin coat. I could try again with the polyurethane and just take steps any avoid dust and/or live with any minor imperfections that occur. Have others has success applying Vallejo water-based polyurethane over Tamiya TS paints, or am I trying to do the impossible? Could it just be a case of not leaving it long enough to cure? Or should I be using a solvent-based clear over a solvent based paint? Would Vallejo acrylic satin be a better choice? Any advice would be greatly appreciated!