The Number1 problem with your airbrush when spraying water-based paint will always be tip dry. The name refers to paint drying on the needle and blocking the flow of paint. It is made even worse when using opaque white.
1. Reduction or cessation of paint flow
Paint flow is diminished by the blockage created by paint drying on the needle. A buildup creates a dam that often breaks while the airbrush is under throttle, causing a flood of paint, or splatter on the surface.
2. Bubbles in the paint reservoir
Bubbles appearing in the paint reservoir are created when blockage of paint on the needle forces the air back through the paint passage. Bubbles may mean that tip dry is occurring, or has occurred in the past. Note that bubbles in the cup can also be a symptom of a loose nozzle.
3. The appearance of paint specks on the painting surface
When paint collecting on the needle reaches a certain buildup it may dislodge itself and land on the painting surface in the form of small tar-like specks of paint. These specks of paint often have liquid cores, so removing them immediately can result in a smear. In most circumstances, it is advantageous to allow them to dry before attempting to dislodge them from the painting surface.
No cure currently exists for tip dry, although developing certain habits will reduce the frequency of tip dry. They are:
- clear the needle pre-emptively every 15 seconds
- polish your needle ( a temporary solution)
- use a little more reducer
These methods can only lessen, not eliminate, tip dry. I have developed the habit of gently picking the needle every time I glance over at my reference. It seems to be the best way to stay ahead of it for me.
I hope this helps, and good luck with all your painting endeavors.