Which of the following is NOT a function of enameling?

The correct answer is that joining metal parts is not a function of enameling. Enameling typically involves fusing powdered glass to a metal surface through heat, creating a durable and decorative coating. This process enhances the aesthetic qualities of metal objects while also offering some protection.

The other options detail typical functions or uses of enameling. Fusing powdered glass is essential to the enameling process, as it refers to melting glass powder to create a smooth coating on the metal. Applying enamel to steel is a common practice in creating colorful, protective surfaces on steel objects, such as cookware or artistic pieces. Additionally, coating glass or ceramics is also part of enameling, especially when decorative effects are desired.

Thus, while enameling involves coating and fusing with glass, it is not used for the purpose of joining metal parts, which is typically achieved through techniques such as soldering or welding.