Tenmokus

TENMOKUS ARE TERRIFIC BROWN GLAZES

Dark brown/black rich glaze, Cone 9, Reduction firing
Glossy, tends to run off bottom of pot
Good companion glazes are Toshiko Orange, Miller White, UH Blue

Tenmoku is a glaze which originated in China, but the Japanese name stuck. The formula used at HPG is made for cone 9 - 10 firing in reduction. Tenmoku glazes are a class of brown glazes which can each have different effects. Some are called “fat” tenmoku, which will run a lot if thick, but are glossy, rich and lustrous. Others are called “dry” tenmoku which is much more stable, does not run and has a more satin finish.

HPG Tenmoku is a brown/black iron rich glaze which gets its color from red iron oxide, and it is very glossy. Bob McWilliams who taught at HPG for a time provided this particular formula. Any clay body works well with this glaze, but porcelain takes good advantage of the glossy finish. Where there is carving or thin edges of the piece, it breaks to a rich rust brown. Sometimes this glaze fires to a deep brown with “flashes” of black from the firing creating unexpected little designs of their own. Metallic crystals can form in this glaze depending upon the clay body and firing, adding extra sparkle to the finish. HPG also has a Tenmoku with more black flashes in it along with the brown finish: Espresso Tenmoku. It is stable.

Interesting effects are achieved using nothing else but Tenmoku on a pot. However, touches or trails of certain other glazes for an accent near the top of a vessel or inside a bowl can add interest. Only a thin trail or light brushing is needed to prevent glazes from “running” off the pot because of added glaze thickness. Toshiko Orange produces a lovely gold accent. Miller White creates a “Milky Way” trail. UH blue breaks into an almost iridescent milky blue, quite celestial.

Tenmoku should be a light coffee cream consistency. One dip of the pot is enough. This glaze tends to “run” in firing, so it is wise not to double dip, and to make sure the bottom of the pot is well waxed then wiped off thoroughly. “Feather” or thin the glaze about one inch from the bottom with a sponge or metal rib, even if there is a waxed rim above the foot. Extra feet on a pot from too much melted glaze is ugly and sharp to touch. Runny glaze is not good for the kiln shelves either.

The suggested application for tenmoku is the pour technique. With the piece upside (rim side) down on a rack over a basin, pour well mixed glaze smoothly around the outside of the pot. This way the glaze tends to collect toward the rim

rather than the foot. Feathering is also necessary toward the bottom. (see Chapter 16 for details.)

Other brown glazes at HPG have different names, but are classified as “tenmoku” and sometimes “kaki” which is Japanese for persimmon.

Kaki Persimmon is a very stable dark brown semi matte glaze, with some tiny crystals appearing deep into the surface.

Ohata is a more red brown stable glaze, very dependable and handsome.

Cecil’s Red is the same formula as Ohata except that the addition of Bentonite to the formula, only 2%, makes for a stable glaze, not runny and rather more red than Ohata. It works well with other glazes as accents, such as Toshiko Orange, UH Blue, G-Black, Miller White.

Both of these glazes have extremely tiny iron crystals which create a deep sparkle in the finish.

Kaki Persimmon, Cecil’s Red and Ohata work well with accents of Toshiko Orange, UH Blue and Miller White. Brian has found that using Toshiko Orange under the top coat of the Tenmokus works best because of the different melting temperatures. Toshiko melts earlier and comes up through the top glaze. Nelson’s Transparent trailed or dotted onto Ohata creates an elegant Tahitian Pearl effect.

Acero is a new stable glaze introduced by Yoko Haar, best used on iron rich clay. Where thin it is brown, where thick it is yellow. Letty Geschwind is the mistress of this glaze quite often.

No toxic ingredients are in Tenmoku or other brown glazes, therefore they are very good for food containers, covered casseroles and dishes, cups and bowls. They are microwaveable and can be baked in the oven when used with HPG high fired clays.

Pat Harwood April 10, 2005 ed jan 2007 January 2009, Nov 2010