I am confused I own an Iwata HP-BCS bottom feed airbrush.I noticed that Iwata recommends a minimum working pressure of 35 psi. So no matter what, is that what I run it at? I have in hand a bottle of alclad II primer and microfiller, no thinning required, directions state to run 18psi.Me dumb... no understand.Thank you.

I would not recommend spraying, at 35psi. 20 is what I keep mine at. If the directions tell you to spray at a certain psi, go with that. Spraying at 35 would likely flood the model.

David, it depends. You have the HP-BCS which pulls from the bottom, and is marketed as a high-flow design for heavier or pre-mixed paints. The HP-CS gravity feed Eclipse that I have requires much less as it is designed for more highly thinned paints closer to the 18-20psi that the Alclad (or the old Model Master Metalizer) requires.

A higher PSI gun is designed to move heavier (thicker) paints by using more pressure and generally has a larger nozzle(0.5mm for example).

The issue is that the paint you have (the Alclad) is designed to be run through a lower pressure airbrush. If you want to use the Alclad with the HP-BCS I would not run that brush higher than 20 psi.

So I can expect the Iwata bottom feed to work well at 20 psi with this very thin paint or do I need to buy a top feed? I do have a chinese knockoff top feed I will give that a try.Iwata is so adamant about the 35 psi. Thanks.

Why not try some test painting on scrap plastic. Start at 18-20 PSI and work your way up a little. I suspect somewhere between 20-25 PSI will be fine.

I had a closer look at the Iwata directions. 'working pressures generally vary between 20-60 psi' some really screwed up instructions. Goes on to say to take full advantage of the Eclipse blah blah blah 35 psi or above is desired....blah.I am thinking to much about this.Thanks guys, for setting me back on track.