This chapter discusses all about grain and liquid enamel. The painting enamel information is in the Supplements and Add-Ons chapter. This page lists some infomation that did not make it into the book.
There are different clear transparent enamels (also called flux and transparent clear enamel). Each of the formulas, when fused to copper, affect the color of the metal. Some, like 2030 and 2008, cause the copper to look pinkish. But some make the copper look goldish. My favorites are 2015 Golden Clear and 2110 Wax Yellow (also called Ivory Beige). 2015 is less golden than 2110, but both are really nice. I'm sure all the other manufacuturers have differences, too, but these are the ones I know.
There are three Thompson enamels currently called Crackle Bases - 1006 (White), 1997 (Black) and 2008 (clear). But the actual Crackle enamels are liquid and their name was changed from Crackle Enamels to Liquid Form Enamel colors, to reflect that they can be used for many more things. Here is some information about these enamels. Note that 1020, Titanium White, can also be used for a crackle base.
The ONLY time this line of Thompson Enamel liquids crack are when they are used over the bases (or 1020). If you put any other Thompson unleaded enamel over the bases, they normally produce a technique called Pull Through. It is incorrect and misleading to call this result crackle enamel instead of pull through. They look totally different - one has cracks like rivers and one has dots. Please do not call this Crackle Enamel.
This enamel chararteristic of soft, medium and hard is dicussed: soft enamels fuse at a lower temperature than medium and medium fuse lower than hard. If you put a soft enamel under a hard enamel, you will probably get pull-through, which may not be what you want. The book mentions that this characteristic is dependent on two things: the enamel's fusion flow number and its softening temperature. Here I give a bit more about this...
Normally, but not always, a low softening temperature and a high fusion flow makes an enamel a soft enamel. Coversely, but not always, a high softening temperature and a low fusion flow makes a hard enamel.
The fusion flow number was obtained in an interesting way. Tom Ellis related that a small pill sized piece of fused enamel is fused to a steel plate. Then the steel is set in a kiln at a certain temperature, say 1450°F, in a verticle position, for a standard period of time. The amount of dripping/flow the enamel causes on the plate is used to determine the fusion flow number.
Enamels with a low fusion flow number (ie: they didn't flow as much) were ones that have a heavier viscosity. Viscosity being the thickness of the enamel when it flows.
All these characteriscs affect how one enamel interacts with another. See the manufacturers specification for these numbers. For Thompson Enamels, see The Thompson Workbook.
This topic is covered extensively in the book, but there is always more to learn. Ora Kuller uses the fact that wet-pack grains straight from the jar will spread when fired. But if you want a wet-packed application to stay where put, use -200 or smaller mesh. Remember, though, that if this is a transparent, it may be more opaque than you want so there is a trade off. Experiement and see what works for you. Also, remember that the higher/longer you fire, the more spread you could get.