Mix Copper red with only water or with water and a bit of water-friendly medium (for example, Sir Pete medium or glycol). Only apply to the tin side of float glass. The firing temperature can be varied between 580°C (1076°F) and 700°C (1292°F) depending on the shade desired. Fire at least 30 minutes and cool slowly (overnight) to allow annealing.
See PELI Glass information sheet for details.