To make Gruyère, raw cow’s milk is heated to 34 °C (93 °F) in a copper vat and then curdled by the addition of liquid rennet. The curd is cut up into pea-sized pieces and stirred, releasing whey. The curd is cooked at 43 °C (109 °F) and raised quickly to 54 °C (129 °F).
The whey is strained, and the curds are placed into molds to be pressed. After salting in brine and smearing with bacteria, the cheese is ripened for two months at room temperature, generally on wooden boards, turning every couple of days to ensure even moisture distribution. Gruyère can be cured for 3 to 10 months, with long curing producing cheese of intense flavor.