Tip dry is acrylic paint drying on the exposed needle tip while you spray, gradually choking the pattern until the brush spits and stutters. It is the number-one “why is my airbrush spitting?” answer.
Management, not elimination, is the goal: a drop of flow improver or drying retarder in the cup slows it, and the standing fix is thirty seconds — pinch a damp swab or brush over the tip, twist, and keep painting.
See it in context in our airbrushes guides, or explore the tools hands-on in The Bench.