to me it seems like tamiya acrylics dont always behave like an acrylic should. i have talked with other modellers locally and we call tamiya paints "hybrid" the reason being is you can thin them with solvent thinners. so this tells me they have a different base than most acylics. this is purely speculation on my part and others but this is my findings. using other acrylics like model master,pollyscale, vallejo , to name a few i havent had this problem. i did with tamiya though. tamiya has a great line of colors i just personally dont care for the way they perform, i have used them in the airbrush on armor models and they worked fine for that application. i just generally dont like them for aircraft. this is only my opinion based on my experimentation.