Dating french candlesticks
Enamels have long been used to decorate the surface of metal objects, perhaps originally as a substitute for the more costly process of inlaying with precious or semiprecious stones but later as a decorative medium in their own right.Whereas paint on metal has a short life and, even when new, is overshadowed by the brilliance of the polished metal, enamelling gives the surface of metal a durable, coloured, decorative finish.For example, turquoise-blue enamel can be obtained from the black oxide of copper by using a comparatively high proportion of carbonate of soda; in the same way, a yellowish-green enamel can be obtained from the same black oxide by increasing the proportionate amount of red lead.
The colour of many enamels is achieved by a change in the proportion of the components of the flux rather than by a change in quantity of the oxide.
All trace of the acid is then removed by washing and by drying in warm oak sawdust.
After the wet powder has been spread on the metal, it is allowed to dry in front of the furnace before it is carefully introduced into the muffle of the furnace (a compartment protected from the flame), where it is heated to the point at which it fuses and adheres to its metal base.
The degree of hardness of the flux depends on the proportions of the components in the mix.
Enamels are termed hard when the temperature required to fuse them is very high; the harder the enamel is, the better it will withstand atmospheric agencies, which in soft enamels first produce a decomposition of the surface and ultimately cause the breakup of the whole enamel.