Controlled heating and cooling to form stable cocoa butter crystals (Form V). Only Form V gives the glossy sheen, clean snap, smooth melt, and resistance to blooming. Untempered chocolate sets soft, melts in your hand, and develops bloom within days.
Dark chocolate: heat to 50–55°C to melt all crystals, cool to 27–28°C to form Form V seeds, reheat to 31–32°C working temperature. Milk chocolate slightly lower. White chocolate lower still. Seeding method: melt two-thirds, stir in remaining third (finely chopped factory-tempered chocolate) to introduce seed crystals.
Seeding method is most forgiving: melt 2/3 gently, stir in 1/3 finely chopped. Test on parchment — shiny and set in 3–5 minutes means properly tempered. You can temper and re-temper the same chocolate multiple times. For ganache, tempering isn't needed because cream disrupts crystal formation.
Any water in the chocolate — causes seizing. Overheating past 55°C. No thermometer. Working in a warm kitchen above 22°C. Rushing the cooling. Pouring into moulds at wrong temperature.