How are vitreous enamel signs made?

[fusion_builVitreous enamel signs are made by fusing powdered glass to a substrate of low carbon steel. This is done by a firing process. First, the powdered glass is mixed with water and sprayed onto the metal, after which it is left to dry. The sign is then fired in a kiln at a temperature exceeding 820°C (1500°F). The powder melts, flows, and finally hardens into a smooth, durable vitreous coating. This forms the grey base layer, which is chemically bonded to the metal. For any additional colour, a separate layer of pigmented powered glass must be applied and fired independently. By using this layered approach, enamelling can produce very smooth, glossy finishes in a wide array of colours.