Sucre cuit encompasses the progressive stages of sugar syrup concentration, from thread (100°C) through caramel (170–190°C), each stage defined by water content, viscosity, and resultant texture upon cooling. A solution of sucrose and water — typically 3:1 sugar to water by weight — is brought to the boil with a small addition of glucose syrup (10–15% of sugar weight) or a few drops of lemon juice to promote partial inversion, inhibiting recrystallisation. The classical French stages are: petit filé (thread, 100–106°C, 80% sugar), used for syrups and sorbets; grand filé (large thread, 106–110°C); petit perlé (small pearl, 110–112°C); grand perlé (large pearl, 113°C); petit soufflé (blow, 115°C); grand soufflé (large blow, 117°C); petit boulé (soft ball, 118–120°C) for fondant and fudge; grand boulé (hard ball, 121–130°C) for caramels and nougat; petit cassé (soft crack, 132–143°C) for toffee; grand cassé (hard crack, 149–154°C) for barley sugar and spun sugar; and caramel (160–190°C). Above 160°C, sucrose undergoes pyrolysis — thermal decomposition generating hundreds of flavour compounds including diacetyl, maltol, and furanones. Copper pans are traditional because their superior thermal conductivity provides even heat distribution and rapid response to temperature adjustments. The sugar must not be stirred once boiling begins; agitation introduces nucleation sites prompting crystallisation. Instead, wash down the sides of the pan with a wet pastry brush to dissolve any stray crystals. A sugar thermometer calibrated in the local atmospheric pressure is non-negotiable — at altitude, subtract approximately 1°C per 300 metres of elevation. Humidity above 60% makes high-stage sugar work nearly impossible, as hygroscopic sugar absorbs atmospheric moisture and loses its set.
Add glucose or acid as an interfering agent to prevent recrystallisation; never stir once the syrup reaches a boil — wash the sides only with a wet brush; use a calibrated thermometer and account for altitude corrections; recognise each stage by temperature and physical test (thread, ball, crack); work in low humidity below 50% for any stage above soft crack
Test your thermometer in boiling water at your elevation before every sugar session — even a 2°C drift changes the outcome; when making Italian meringue, start whipping whites when the syrup reaches 110°C so both are ready simultaneously; plunge the pan base in ice water for 2 seconds to arrest cooking immediately at the target stage; keep a bowl of ice water beside the stove for safety when working above 150°C
Stirring boiling sugar and triggering mass crystallisation; failing to add an interfering agent, producing grainy results; using an uncalibrated or slow thermometer and overshooting the target stage; neglecting to wash down pan sides, allowing seed crystals to form; cooking sugar in a humid environment where hard crack pieces become sticky within minutes
Gaston Lenôtre, Lenôtre's Desserts and Pastries; Hervé This, Molecular Gastronomy: Exploring the Science of Flavor; Le Cordon Bleu, Pâtisserie and Baking Foundations