The coat before the fry: dredge, crumb, batter

How to tell it is going right

• The coat is continuous before it goes anywhere near the fat: held up to the light, no bare patch of food shows through anywhere, seams and thin edges included.
• It is bonded rather than resting on top: a gentle shake sheds loose dust only, and the coat does not slide off as a sheet when the piece is handled.
• It bubbles hard and steadily from the moment it enters the fat, and the bubbling visibly slows as it finishes; those bubbles are the surface water leaving, and a quiet entry means the fat is too cool.
• Out and drained, it is an even gold-brown all over and it is still crisp several minutes later on a rack; a coat that softens within a minute of coming out never lost its water.
• Broken open, there is no paste of raw flour under the crust and no hollow gap where the coat has lifted away from the food.

Where it goes wrong The fat was below temperature or the pan was crowded, so the coat drank fat instead of sealing against it: it comes out pale and heavy, greasy to the fingers, and slumps off the food as it cools.