Vitreous enamels are a form of soft glass with a melting temperature between 700 and 800°c, coloured using different minerals and elements — i.e gold is used in pinks, cobalt is used for blues.
Cloisonné
Cloisonné is a technique that is believed to have originated in Ancient Egypt. The French term refers to a form of artisanal decoration in which fine strips of metal are applied to a metal surface in closed shapes called cloisonnés. Multiple thin layers of enamel are individually applied into the cloisonnés and the piece is fired in the kiln after each application.
Plique-à-Jour
Plique-à-Jour (French: letting in daylight) is a vitrous enamelling technique where enamel is applied into small cells with no backing and fired in a kiln. The enamel powdered glass enamel ground with water and small amounts applied to the cells cut from the metal. The enamel is suspended from the cells and kiln fired. It is a challenging labour intensive technique.Transparent enamel is used so that the light can shine through the charms, like stained glass.
Care
Enamel is a durable glass-like substance that is resistant to colour fading. Avoid contact with cleaning agents, perfumes and sanitisers. It is advisable to remove enamel rings if they are to come into contact with cleaning agents as some of these can discolour the enamel. Keep the enamel jewellery in the box you received it in, or something similar for protection. Enamel jewellery should never be put into an ultrasonic cleaner. Do not use jewellery cleaning fluids to clean enamel - use a soft toothbrush and warm water.