Anything that shows, anything narrow, and anything past the format's ceiling.
It cannot lay a finish coat (marks and sheds), it overhangs panels and floods profiles (that's the 3″ and below), and it is a poor latex brush (natural bristle limp in water).
Most distinctively: it is not the tool for a genuinely large field of finish — a whole wall, a floor, a full elevation of siding in paint.
A 4″ chip drags dry and loses the wet edge on true production area; that work is a roller's, a pad's, or a fitted brush's, and pushing a disposable chip past its ceiling is how you get lap marks and a dry, streaky coat.
a 4″ face carries a lot and skins or drag-dries if you dawdle — lay long single-direction strokes and keep moving, especially with stripper (never re-brush) and fast adhesives. Respect the ceiling: if you find yourself scrubbing to keep the surface wet, the field is bigger than a chip brush should do — switch to a roller or a fitted brush rather than fighting the format. Load to a third and wipe one side to stop the wide bundle drooling. Disposal: stripper-, oil-, and solvent-laden bristle self-heats — dry flat and separated or drown in a sealed metal can, never bagged wet. Buy several: wide jobs cure brushes solid; a 4″ chip locked with resin or contact cement is done.
Asked before buying
BUYER QUESTIONS, ANSWERED BEFORE YOU ORDER
What's the 4″ chip best at?
Mass application of a brush-killing liquid to a fully open flat — a slab door, a tabletop, siding — in the fewest strokes, with a brush you bin after (§2a).
Why not an even wider chip?
Four inches is about the ceiling for a loose-set bristle bundle; wider, it can't carry or control the load — the next step up is a roller or a fitted brush, not a bigger chip (§1, §5).
Difference from the 3″?
The 4″ suits fully open faces; the 3″ fits framed panels without overhanging (§5).
Can it paint a wall?
No — it drags dry and loses the wet edge on real production area, and it marks and sheds; use a roller or fitted brush (§4).
Disposal after stripper or oil?
Oily-rag hazard — dry flat and separated or drown in a sealed metal can (§3).
