Tempered chocolate sets firm, snaps cleanly, and has a glossy surface. Untempered chocolate sets soft, streaky, and dull. The difference comes down to how the cocoa butter crystals form as the chocolate cools. Tempering controls that process deliberately. It is not difficult, but it requires a thermometer and some attention to temperature.
An afternoon with a marble slab and a lot of patience
Elspeth, who makes hand-dipped chocolates each winter in Ballarat, spent years producing truffles with a greyish bloom on the surface. The bloom is not mould. It is cocoa butter that separated during cooling because the chocolate was not tempered. She learned the tabling method: melting chocolate to 45 degrees, pouring two-thirds onto a cool marble surface, working it back and forth until it drops to 27 degrees, then combining it with the reserved warm chocolate to bring the whole batch to 31 degrees.
That three-temperature sequence encourages a specific crystal structure in the cocoa butter, called Form V, which is stable and gives chocolate its characteristic snap. The marble slab is traditional but not essential. A bowl over cold water achieves the same result with more stirring.
For baking into cakes or brownies, tempering is unnecessary. It only matters when chocolate is the coating or the finished product itself. Knowing the distinction saves a considerable amount of effort on the wrong occasions.