Properties of Opalescent Enamels. Okay, get ready for this. Most modern day opalescent enamels are not truly opalescent but rather semi transparent. A true opalescent is a mixture of two immiscible enamels. (Immiscible Definition
Immiscibility is the property where two substances are not capable of combining to form a homogeneous mixture. The components are said to be “immiscible.” In contrast, fluids that do mix together are called “miscible.”
Components of an immiscible mixture will separate from each other. The less dense fluid will rise to the top; the more dense component will sink. This can also be true of solids but in the case of enamels, it is referring to the molten state.)
The old leaded Thompson were true opalescent enamels. In the case of their 835 Opal White, the glass was immiscible unless fired too hot. If you fire them too hot they become miscible and the resulting glass becomes an opaque. According to the late (great) Woody Carpenter, these enamels also contained arsenic. The “too hot” varied from one batch to another. I have a rather large container of 835 that goes opaque at about 1325 degrees and so as long as you fire under that temperature, your results will be a glorious true opalescent enamel. It should be noted that most medium fusing enamels are meant to be fired hotter than this. It is possible to get them to a glossy stage at 1325 but it will take 3 minutes or more for a small jewelry piece. In actuality, it doesn’t matter how many times you fire a piece as long as it never gets hot enough to change the chemical makeup and cause it to go opaque. Because they are so delicately fussy about temperature, you may find that firing on a layer near the end is safer for you but it really is about the temperature.
The Japanese opals are all semi transparent and not sensitive to overheating. The colors are quite lovely and troublefree but not actually opalescent enamels. Have a look at a Faberge Egg in person some time for an example of Opalescent Enamel. They are delicious.
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