That Red Tenmoku Stuff, Mostly --

As I've stated repeatedly elsewhere, I'm attempting to get back to a particular "Red Tenmoku" glaze that I developed some time in 1998 if memory serves. That glaze involved only four ingredients: brick clay, wood ash (unwashed), silica, and red iron oxide. The original proportions were 40:40:16:4, but that was before I ran the stuff through a sieve. Also, that was with fireplace ash that consisted mostly of Duraflame (tm) logs, with some paper, cardboard, and other wood. It turns out that ash is an extremely variable substance, and my current ash (from a fireplace in Towson, MD) is probably greatly different.

These and other factors make the redevelopment of this glaze a fraught and drawn-out process. Mind you, it's fun, and I'm coming up with lots of other glazes that I like; but I still haven't got a Red Tenmoku, and it's driving me up the wall.

This journal starts in May of 2000, and I hope I'll be able to continue it through to several satisfactory conclusions, with photos of representative pieces as well as the ubiquitous images of little glaze-test tiles...

...But this time (Mid-May, 2000, test B V), not only did I get something reasonably interesting, I got something that doesn't run quite so badly.

Here is that test, bracketed by the preceding and following ones. B IV runs, and is brown instead of red; B V is interesting, but still isn't red; B VI is opaque. As you can see, my path is a wobbly one. (Argh!)

420 x 480 version

640 x 480 version

640 x 480 version

B VI seems to me to be fairly close to a "hare's-fur" glaze. I liked it well enough that I applied it to a teacup, which worked out fairly well.

A Bit of Technoid Scunge

My general impression is that:

• More clay makes it more opaque and browner;
• more ash makes it clearer, stringier or "leggier" the way wine is said to be leggy in the glass (if enough ash is present), and greener;
• more silica makes it more beige, and frequently more opaque;
• more iron oxide makes it darker and runnier (and usually browner as well);
• ...and I am now hoping that more calcium will make it runnier and redder, so I can balance that against the rest to get to the goal. I have just dipped a pair of 32.5:31:12W:20:4.5 test tiles, and I should have results by around Halloween of 2000. (The first number is the percentage of brick clay; the second is the wood ash; the middle number, if present, is Whiting (W) or Wollastonite (O); the next-to-last is silica; and the last is red iron oxide.)

"B IV" is 47:35:10:8; "B V" is 50:30:12:8; and "B VI" is 48:28:14:10. As you can see from the images, reducing the ash from 30 to 28 and increasing the silica from 12 to 14 is enough to change a hare's-fur glaze to something much more closely resembling milk chocolate. (This sort of large change in appearance from moderate changes in composition is typical of some glaze families but not others.)

Here, to show you more of what happens when I vary the composition a bit further, is 55:25:14:6 on stoneware:

640 x 465 version

If you want to see some vaguely comparable tests using synthetic wood ash, you can take a look at Episode 6 of my journal. Unfortunately I was using a different numbering system at that time (total of 20 parts rather than percentages), but it's easy enough to convert.

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Last modified: Wed Jan 3 20:37:27 PST 2001