Jewellery enamel is not a plastic and no wonder that many people do not know what jewellery enamel is. Enamel, before I had started to do professionally, was incomprehensible material to me. It was synonymous with battered cooking pots from the time my grandmother.
But in times of our grandmothers, there was no better protection against corrosion of iron. There were no zinc electroplating or sophisticated chemistry of coating. So there were enamelled not only kitchen pots but also iron pails and even cast-iron bathtubs.
When asked what the true enamel is, I say: it is "something" between glass and porcelain. It is ceramics. Silicate compound which has feature that at high temperature can melt and fuse with a metal base and even produce a beautiful glossy finish. High temperature means red and yellow glow of the melting furnace (600 - 900 ° C).
The best quality of enamel is jewellery enamel. It can be used for copper, few sorts of brass, silver or gold. On its surface can be applied ceramic paints to make a pictures. But it needs to be fired again. Such an image burn-in an enamel is eternal. Never mind a bath in the sea or solar UV radiation. It can lie deep into the ground for a few hundred years and its luster and colour does not vanish. Jewellery enamel has a range of colours and can bear a various transparency. Semi-transparent enamels are called opalescent. Generally each enamel can be grind and polish even if the work is really difficult.
Enamel technique lies in the cleaning and preparation of the underlying metal as well as in cleaning the enamel before using. The underlying metal is first annealed in a kiln to release tension caused by rolling or bending. After cooling of the metal it is pickled in acids to remove oxides and dirt. Enamel is cleaned in a different way. If is already powdered enamel the delicate oxidized proportion must be removed. And then... Should I go on? It's for a long. I rather go to more fun - firing (or burning).
How to fire enamel? So I will answer to you exactly: it's alchemy. The firing must be long enough for melting when the surface of enamel becomes glossy but not so long that deadburned. It takes experience and practice.
A word in conclusion: as well as the enamelled pails are disappearing, many companies which produced enamel or knew how to work with it disappeared too. I suppose that fired enamel is and will be less and less. Its disadvantage is the high cost - not only a material but also its application. And finally there is the substitution of enamel by polymers. Plastics even if they are softer and suffer in direct sun or in the sea, they are cheaper. Working with them is quick and easy. And sure, merchants call them enamel! So what with that? I'll tell you. If you do not want to include plastic substitutes to your family treasure, you have to focus your attention on the enamel surface:
1) Enamel conducts heat better than plastic. If you touch it is cold - enamel removes heat of your skin. On the other hand plastic isolates more. Touching the acrylic, epoxy, polyester or simply a hydrocarbon polymer is warmer.
2) Enamel is much harder than its substitutes. For example a common iron can never scratch enamel. Iron nail can be blurred on enamel and create a black line which you can wipe off with a tissue. Epoxy substitutes can be scratched easily (that is why to avoid them in your own interest).
3) If you have a magnifying glass look at enamelled metal and enamel. You will find a tiny oxide layer - sign of burning - on their interface. If it is a real transparent enamel, it will reveal some tiny bubbles that are released by high-temperature oxidation of the metal base. Substitute does not have the oxidation layer. Transition metal/polymer is completely clean. The only exception of this rule is professionally performed enamel on high quality gold alloy, respectively on the pure gold. There we do not find a layer of oxidation.
In the end I'll tell you my funny experience from jewelery fair. I saw a trader proving the quality of his enamel products putting them to the fire with lighter. It's true. Enamel can not burn off with a lighter but polymers can easily. Nevertheless, I can not recommend this drastic method to you for its destructive effects.
jewellery enamel specialist