What Is Tempering?
The short answer
Tempering is heating, cooling and stirring melted chocolate so its cocoa butter sets in one stable crystal form. Tempered chocolate is glossy and breaks with a clean snap. It also shrinks slightly as it sets, which is why it drops out of a mold, and it resists bloom for longer.
How it works
Cocoa butter can crystallize in six different forms. Only one of them, form V, gives the gloss and snap people expect from a good bar. Melt chocolate and leave it to cool on its own and you get a mix of unstable crystals: the surface sets dull, soft or streaky.
Tempering steers the chocolate toward form V. The usual path is to melt it completely, cool it until crystals start to form, then warm it a little so the unstable ones melt again and the form V crystals are left to guide the rest.
At home this is done by seeding, tabling or in short bursts in a microwave. Workshops use tabletop tempering machines, and factories run continuous ones. The right temperatures depend on the chocolate, so take them from its packaging or data sheet rather than from a universal chart.
Compound coatings made with vegetable fat generally skip this step.
Where you’ll see it
In recipes for bonbons, bars and dipped fruit. On couverture packaging, which often prints its own tempering temperatures. On spec sheets for tempering machines.
Related terms
The science behind it is in cocoa butter polymorphs. Poor tempering is a common cause of bloom. Compound chocolate is the usual example of a product that needs no tempering. Seeding, tabling and the temper test are covered in the glossary list.