There’s a discussion on the WarmGlass board right now about reactivity in glass, always an interesting subject wherever two glass artists with ruined projects meet.

Molten glass will respond to minute changes in temperature (that’s how glassblowing works), to the atmosphere and to the presence of other substances. That’s why melting glass together doesn’t always deliver the same color as stacking the glasses cold. Red plus white may just equal black.

Between them, Uroboros and Bullseye make about 200 or so different colors of 90 COE glass and no, I’m not going to get into a discussion of COE vs. “compatibility.” As near as I can tell, there are also about 140 different colors of powdered and crushed glass. If you know how to combine them, your palette expands enormously.

Bullseye publishes a color reactivity chart for its glass rods that’s quite useful, but it doesn’t really tell you what the color looks like, just that it reacts. Most glass artists, therefore test color reactions before wasting expensive glass and kiln time.

I make mine by crafting divided glass trays out of clear glass and superglue, filling each cell with a carefully measured (by weight) combination of glass powders. I use the fired panels to choose frit tints for my projects.

Usually I’m adding a strongly colored powdered glass to a neutral “base glass,” and so that’s where I generally test. Here’s a good example:

In this panel I’m testing BE Lightning White (I think it’s called “Translucent White” now) with reds, oranges and yellows (starting from the top, BE Medium Amber, Red, Pumpkin Orange, Orange, Marigold Yellow, Red Orange, Tangerine, Tomato, Pimento). The combinations are lovely but two colors–BE Red Orange and BE Red–have reacted with the LW to form dark brown, almost black. That would have been disastrous if I’d expected hot orange.

I’ve done about 100 panels to date, and they’re an immense help when designing pate de verre and casting. To the right you’ll see what happens when you combine BE French Vanilla with different BE greens. Notice that most of the greens are OK, but French Vanilla with BE Light Aventurine or BE Jade Green makes a dark grey that turns to black as you increase the proportion of French vanilla. Uroboros Spearmint has a slightly less

intense (but similar) reaction. On the right (FV with neutrals), notice also that BE Light Bronze is also reacting with the French Vanilla, and there’s a minor reaction going on with Light Peach Cream.

Here’s another example. If you put powdered reds, oranges and golds on BE White (Left, below), the colors stay pretty true. If you put them on BE Dense White (right, below), you get reactions:

At some point I’m going to figure out how to put all these panels in some kind of table on morganica. For now, they make pretty good wall decorations and invaluable guides to customizing my color palette.