Testing. Testing.

January 30, 2016 Hamish Jackson

It's official: we are in the bleak midwinter (well, we were when I started writing this post anyway). Precipitation from the sky is no longer liquid. It's whiter, colder and you can't see through it. Riding my bike down to work has become treacherous so I've been walking instead; carefully following the paw prints of one of the neighborhood felines....

We live worryingly close to the Carolina Tiger Rescue.

Its been an exciting couple of months at the Hewitt Pottery. The workshop is in a state of flux. Our normal routine has been abandoned for the moment in order to pursue new materials and glazes. Before Christmas Mark was recently awarded a United States Artist Fellowship which came with a significant chunk of prize money. Some of the funds have been appropriated for research and development into new glazes from local materials.

View of Mark's house and the pottery from across the pond.

Just before thanksgiving last year Mark and Adrian went on a mission into the NC countryside, coming back with several different types of granite, feldspars, and other potentially useful materials such as apatite and spodumene.

Raw materials.

Since then, Adrian, Mark, I and Stillman Browning-Howe (the next apprentice who will be replacing Adrian) have been processing these materials to make them usable: transforming them from rocks into powders. First we calcine them in the bisque kiln, then tamp them to break the pieces down to pea-size or smaller. Next they go into the ball mill with water for eight hours or so, which breaks the peas down to very fine particles. We empty this out and dry it in large shallow beds. Some of the material settles out badly, which makes it more challenging and time-consuming to transfer to the drying beds. The process is considerable. Lots of moving rocks and digging slurry out of plastic bins!

Apatite out to dry in the sun because we needed some to mix a glaze ASAP.

Close up of the apatite.

Mark came up with various triaxial blends using the new materials, mixed up small batches of them (50g) and applied them to test tiles. We performed a couple of test firings in the small gas kiln and tinkered with the recipes. Whilst all this was going on, we were making pots and bisquing them ready for full tests.

Test tiles galore.

Test tiles.

These were some shinos I tested (most of them not applied thickly enough).

Next stage was mixing up 5lb-20lb batches of the glazes we liked best and trying various combinations on our pots. We are also experimenting with some raw glazes but for these you need approximately 25% clay which tends to muddy the glaze quality. The granite celadons especially look better with less clay making them only suitable as bisque glazes.

Glaze measuring station

Some of the new glaze tests.

Bisque pots awaiting glazing above, raw glazed pots below.

Bisque-ware

Some little yunomi I made for tea or whisky, or whatever tipple you prefer.

Mixture of mugs and yunomi.

Some of my tumblers.

Some of Mark's bisque pots. I love these--they remind me of Greek or Roman wine vessels.

Mark in the midst of a Sunday morning's glazing.

Mark's mugs. Slip trailing in progress.

This past week we loaded the front chamber of Mark's new kiln (built in 2007) and fired it through Wednesday, Thursday, and Friday. Despite being only the front chamber, it fit a significant amount of pots. We placed different glazes all over the place to see how they react to higher and lower temps. Its very exciting. Now all we have to do is wait and hold our breath! We unload in four or five days and I'll post some photos of the results then.