airbrushing.

Sounds like a back pressure problem-check your AB's nozzle.

how are you mixing the paint? don't shake, contary to Mr Bond

If you are getting NOTHING out of the tip (no paint, no air, no nothing) the tip IS clogged. That will cause the blowback into the bottle that you are seeing. A clogged or partially clogged tip causes the vast bulk of airbrush problems and virtually every time it happens to me I swear the tip is clear.

Take the head off, don't lose the Teflon washer between head and body, and soak it in laquer thinner overnight and that should clear it.

if the tip is clean and it still does that make sure the head is tight on the body.... don't tighten it too much (i.e. with a pipe wrench ) but I've had that happen when the head is a bit loose.

can anyone tell me how to adj tip to get started ?

you shouldn't have to adjust the tip... if you are getting air bubbles in the paint jar as bolter is you need to check for paint blockage in the tip, make sure the head is tight and make sure the breather hole in the lid of the paint jar (if it is siphon fed) is open...

If that's not what you were asking let us know and we;ll be happy to help you more!!!