by bkrownd » Thu Mar 13, 2014 10:41 am
I discovered an interesting thing. The 9 MDF sheets were each a little different color and thickness. All had smooth surfaces, but the final paint texture on each MDF sheet is different, even among sheets on the same panel. The hardest, thinnest and smoothest MDF sheet (originally almost a glossy surface) has a much smoother paint surface than any of the others. Most have a somewhat rougher surface, and one is really rough like sandpaper. They were assembled into 3 panels of 3 sheets and painted at the same time, and in fact the roughest and smoothest sheets are next to each other on the same panel. But all of them were smooth and dusted clean before painting, and I didn't notice such a difference in the primer surface.
So, choose your MDF very carefully. Maybe some kind of sealer would have helped?