The ideal proof time for croissants at 31 °C is 60 minutes.
Proofing is the fermentation stage after croissant dough has been laminated, cut, and shaped. Yeast becomes active in the warm dough, producing carbon dioxide that inflates the dough’s internal bubbles. Those bubbles later help create the pastry’s open, layered crumb.
The 31 °C figure is a controlled reference point, not a universal kitchen rule. Proofing time changes with yeast quantity, dough temperature, room humidity, dough size, and the condition of the butter layers. Warmer conditions can speed fermentation, but excessive heat may soften or melt the fat and damage the lamination.
Croissants are often confused with puff pastry because both depend on alternating dough and fat layers. Unlike ordinary puff pastry, croissant dough contains yeast, so fermentation contributes substantially to its rise. The best practical test is not the clock alone: properly proofed croissants look noticeably expanded and feel light and delicate before baking.