Separation Ename (SE)l is a specially chemically formulated enamel that, when painted on top of a few layers of fused enamel, will change the viscosity of the area to spread and show the layers below. The project in the book is written by Tom Ellis who usually uses this supplement with patterns to very nice effect. Others use it with non-pattern/abstract designs.
Tom Ellis has recently given me more information about Separation Enamel...
When Separation Enamel is taken into the solution (or dissolved into) the enamel, it not only changes the viscosity of the enamel, but to some degree it changes the surface tension of the glass. What this does with transparents is to concentrate and darken the transparent color in some areas and lighten the color in others. If you apply two parallel lines of Separation Enamel and then fire, the area between the lines will darken and the lines themselves will lighten. This does not show the same way if applying directly on an opaque enamel (2 lines on an opaque doesn't really do anything). See the detail of Tom's bowl below.
Keep in mind that opaques don't show concentration of color as do transparents - that is, more layers of a transparent will darken the color (one way to shade a transparent) where as more layers of an opaque remain the same. This is one of the physical occurrences of what makes the pattern in Separation Enamel - it is the contrast between dark and light colors. Thus not all color combinations have enough contrast to show a pattern well. Tom recommends using 2110 (Wax Yellow also called Ivory Beige) as a base layer and then 1030 (Foundation White) as a second layer, with a medium to dark transparent as the 3rd layer. The book describes using a light opaque for the 2nd layer, but white will always give you a contrast.
If your experiment doesn't come out as you had wanted, think about this contrast of colors, the thickeness of each layer and the amount of Separation Enamel you have applied. These, along with the firing info below, make a difference in your results.
Firing is also important:
Here is a test of various soft/med/hard enamels to see how they affect the SE process. Tom suggests using a 5” square piece of copper. Make sure to make a map of what enamels you used so you remember what you did. Also, to remember the orientation, I suggest you cut a bit off one of the corners, say the upper right corner.
Here goes: you are going to lay down enamels to form a 3x3 grid:
I’d appreciate hearing back from you on what you feel you learned from this test.
Piece Made from Book Instructions
Here are some pieces made by using the book's instructions. Note the one who took a photo of the piece before firing, a great way to remember what you actually did! These were done in a class with teacher Ingrid Regula, the writer of the Basse Taille project in the book.