Lamination

Lamination

Lamination is the process of enclosing a sheet of fat in dough and folding it repeatedly, so the baked result separates into alternating layers of dough and fat rather than baking as one mass.

The layer arithmetic

Layer count is geometric, not additive, and the folds multiply.

• A single or letter fold, in thirds, multiplies fat layers by 3.
• A book or double fold, in quarters, multiplies them by 4.

Three letter folds, the usual croissant treatment, gives 3 x 3 x 3, which is 27 fat layers. Six letter folds, classic puff pastry, gives 729.

More is not better. Past roughly a thousand layers the fat films tear and merge into the dough, and lift falls rather than rises.

The temperature window

Fat and dough have to be at a similar plasticity, in practice somewhere around 15 to 18 degrees Celsius. Fat that is too cold shatters into shards and punctures the sheet. Fat that is too warm is absorbed into the dough, the layers merge and you get bread.

Lift comes from steam: water in the dough turns to vapour and forces the layers apart, which is why laminated dough needs a hot oven. Croissant dough is yeasted as well, so it rises twice. Puff pastry relies on steam alone.