White enamelled dials were first introduced in England in the 1740s for watches, and for bracket clocks later in the 18th century. Enamel dials were more legible than the engraved and silvered type, and were made by melting a vitreous enamel on a copper base. As the muffles used in the process were only suitable for small objects, it was difficult to produce the larger dials required for longcase clocks, which are therefore extremely rare. Another drawback was that the enamel surface was brittle and tended to crack or flake if subjected to even a small amount of shock or torsion, especially where the dial feet were riveted into position.