Ruth Ballou on sat 25 aug 07
For all the manic glaze testers out there, Curries Gridders and others, here's what I do. Grids, stacked 3 or 4 high, with wadding between them. I also make 2" - 3" square test tiles with an area of texture on part of the tile. These tiles are fired upright in a rack that I make using a large loop tool pulled down through a block of clay. I then press a test tile (a special one that is slightly thicker than the others to allow for shrinkage) into the resulting coil to create slanted slots to hold the tiles upright. Sorta like a taco holder (or toast rack for the Brits out there), but a lot smaller. Quick and easy to make and can be used green the first time, and reused multiple times after the first firing. The racks solve the problem of firing a tile upright: no "L" shape that makes it difficult to store after firing.
Each rack has slots for 6 or 7 tiles. The upright firing position gives information about how much the glaze moves, and fit more efficiently into the kiln. I also do an overlapping second dip on each tile so I can see the difference between thick and thin applications. The backs and bottom edges of the tiles are unglazed. The top edge is glazed to give info about a rim. Base glazes get stripes of oxides to give me an idea of which ones are worthwhile pursuing. I criss cross some likely colorant combinations. I figure as long as I'm testing, I may as well get as much information from each tile as I can and these little extras don't take much time to do. These down and dirty oxide tests are plenty to give an idea if a colorant or combination is worth a more detailed line blend test.
The first racks were a bit crude and some tiles fell over. But it's simple to adjust the design to make them very stable. Look for a large loop tool or make your own. Something approximately triangular in cross section would be about right. Or two racks can be smushed together to make one wider one if you can't find a large enough loop tool.
Each tile is numbered sequentially; a log has all the firing information. The digital age makes it easy to take pics of cones and add them to the file. Recipes are also in a glaze calculation program. I don't generally take pics of the tiles for the programs; too time consuming and I'd much rather look at the tiles. The tiles file neatly in shoe-boxes, labeled on the outside with the #'s of the tiles within. Tiles that belong to a Currie Grid are mounted on foam core with sticky back velcro. These also stack neatly. I think of these tiles as my personal Encyclopedia Britannica of glaze theory, as they've all been fired in my kilns with my firing schedule. I learn more every time I examine a grid.
I'm away from my studio at the moment. I'll post some pics when I get back to Belgium at the beginning of next week.
Ruth Ballou
Only slightly obsessive compulsive
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