It's a new airbrush, and here is a link to it: http://www.iwata-medea.com/index.php/products/hp_ch
I'm not used to the additional screw on the bottom, so I've been adjusting that back and forth during all my testing to see if that is the problem.
The paints I have used are Vallejo Model Air straight from the bottle and Vallejo model color thinned with water.
The compressor could be the weakest link. It's a smaller compressor with 2 condensation traps and it has no tank. It runs up to 60 PSI, but I keep it around 20 PSI (15 PSI with trigger pulled). Here are my problems.
1. If I try to get it too small by screwing in the rear screw and tightening the bottom screw it eventually stops working and every now and then pushes out paint intermittently. I'm thinking I may need to thin down Model Air a bit more.
2. If I try to do very wide it will sputter out paint splashes around the edges.
3. If the bottom screw is not fully open or fully closed, the paint bubbles in the cup. I'm not sure if this is a problem or not, but when you are talking about small amounts of paint the paint is formed into bubbles and none is reaching the nozzle.
4. If I spray straight water out of the brush I sometimes can get sputtering. Not a solid fine mist but intermittent.
Any ideas before I go home tonight and start playing with it more?