After shaping and drying, green bricks are fired in a kiln up to 1350ºC to form a ceramic bond giving them strength and integrity. Coke and black coal were used as a fuel to fire the kilns up to 1965 when they were converted to use heavy fuel oil. Probably the most significant improvement to firing was made in 1974, when the change to natural gas occurred. Quality was improved and rejects reduced with the even control of burning temperatures. After 72 years there was no more landmark black smoke from the chimneys, only the occasional wisp of steam.