Here are some cups and teapots made by potters at the workshop in my studio this past Saturday. White earthenware clay – LF06 from Seattle Pottery Supply – was used to build these pieces. Participants worked with conditioned clay slab, stamps, rollers, and texture mats to form and decorate their pieces, and all pulled handles on their teapots after practicing handles on their cups. We all decided to call the process “handle smoothing” instead of “handle pulling”.
I’ll be posting the whole teapot making sequence on the blog in the next week or so. In the meantime, here’s the low-fire glaze recipe that we talked about during the workshop and saw on pieces in the studio. This is an extremely well behaved, paintable Gerstley Borate glaze that comes from Gail Kendall. It should be thick and goopy – about the consistency of yogurt, and is easy to paint on pieces. I like to use one of those cheapie disposable brushes from Home Depot, but any wide flat brush with coarse bristles is fine.
You can paint this glaze inside a cup fairly easily, but it is a problem to get it inside teapots or tall pieces, or very small pieces. I use Georgie’s lowfire base glaze for pouring inside pieces. I am not sure if this glaze is still available, but every pottery supply house offers a dry lowfire clear. These glazes are often hard to dip on smoothly, and sometimes have unpleasant opaque areas where the glaze is too thick. The Georgie’s base glaze is very nice sprayed on the outside of pieces, but I could never get a good surface by dipping or pouring. But it makes a great liner glaze, and is completely compatible with Kendall glaze. Over or under, the two glazes melt together smoothly. Here’s the recipe:
Kendall Paintable 04 Glaze
55% Gerstley Borate
Rich Green – 8% Copper Carbonate
Cobalt Blue – 2.5% Cobalt Oxide
Inky Blue – 6% Copper Carbonate + 1.5% Cobalt Oxide
Rich Yellow – 6% Rutile
Cream – 3% Rutile
Warm Clear – 1.5% Rutile
Ochre – 7% Umber
Medium Blue – 2.5% Cobalt Carbonate
Mason Stains – 4% typical, more required for all pink, purple, red
The “Cream – 3% Rutile” variant is what was used on the pieces seen in my studio.
This glaze should be thick! If you try to thin it enough to pour, it will not yield a satisfactory surface. I paint three thin, even coats on each piece, taking special care under handles and around details. It will crawl if it is too thick. Let each coat dry before applying the next.
The slab for the reliquary is bisque fired and ready for the mat to be made. I will be doing that later today, and will also be testing three different seal/release products.
It was a very close fit going into the kiln…. but I wanted the largest slab possible. I have tried standing the slabs on edge for firing, but they bowed in firing. I was still able to make useful mats from those slabs, however.