Lamination creates hundreds of alternating layers of dough and butter through repeated rolling and folding. When this layered structure hits oven heat, the water in the butter turns to steam and forces the dough layers apart.
The butter block needs to be 11-16C — cold enough to stay solid, warm enough to bend without shattering. The dough should be slightly cooler at 2-6C. Each letter fold triples the layers. Three turns gives 81 layers for croissants. Rest 30-45 minutes between turns to relax gluten and re-chill butter. European butter 82%+ butterfat performs better than North American standard 80%.
Feel the dough before every roll — if it is fighting you, put it back in the fridge. Brush excess flour off before every fold. Cut with a single decisive motion — pressing down compresses the layers at the edges.
Butter too cold — it shatters into chunks. Butter too warm — it absorbs into the dough. Overworking the detrempe. Not resting between turns. Over-proofing yeasted laminated dough.