(13 August, 2000)
[Note to copyeditors: I know, "Over" shouldn't be
capitalized, because it's only 4 letters. I did it to
match with "Under", because local consistency won the
toss of the penguin this evening.]
The red vase that I show in the previous Biscuit has now survived biscuit firing (that's another term that is loosely equivalent to what we usually call "bisque" these days in pottery). I keep forgetting to bring it back to the lab & wax the base, but that's okay because I still need to make a glaze test on stoneware, and if I wax it now, the wax will probably fall off before I get around to glazing the fool thing.
Meanwhile, I have made two more of a similar sort; but the first one is easily the best, or so it seems to me.
For what reason I know not, I decided to make a black glaze. I guess part of this is the fact that the famous "Rhodes Black" glaze is very lovely, and has only about three ingredients... one of which is no longer available. I figured my magic brick clay would substitute well, so I tried it. My balance was slightly off, but the result is definitely a keeper. Unfortunately, a silvery-black glaze is so difficult to photograph that I still don't have a picture I really like.
On the other hand, I've got a second test of that glaze in the kiln now, and if it works I'll show a photograph of it regardless: it should have silvery crystals on a black ground (presuming it works about the same way on stoneware as it did on porcelain), and a swipe of golden crystals across the silver. This may, in practice, prove to be a bit sterile, but perhaps I'll luck out and it will carry enough interest to work. (That, or I'll get to be good enough at decoration that it will work even if the glaze itself doesn't have enough going on in it. ...I should be so lucky...)
I am also going to flux it a bit more heavily, and see whether I can get something closer to Rhodes's glaze out of it. I think I have a fair chance, and I stand to learn a lot regardless of whether I succeed.
I have just read the excellent Chinese Glazes, by Nigel Wood. While this book suffers from some typical British copyediting problems (more than just a few typos, inability to distinguish "that" from "which" ["which" is for dependent clauses; this is not rocket science], and so on), the book is absolutely fabulous. Wood goes through just about the entire history of Chinese ceramics, giving photos of exemplary pieces and discussing materials and techniques. That would be good enough all by itself, but he gives analyses of bodies and glazes both. If he stopped there, the book would be really fine... but he doesn't. Instead, he closes by presenting formulas that approximate many of the ancient glazes, but using modern British materials. (He even includes a version of one Japanese glaze, a Kaki [persimmon-color] from Mashiko, with some hints about good effects to be had from it.)
With all this, Wood presents a rather solid argument in favor of adding a "straight percentages" model for thinking about and dealing with glazes to our usual R2O:RO:R2O3 pseudomolecular model, which was invented by Hermann Seger in the 1800s. Having been extremely uneasy with Seger's method since I first encountered it (Does B2O3 go with fluxes or glassformers? To what extent have you reduced the iron in your glaze, and how do you note that in the formula, especially when you won't know the answer until after you fire? P2O5 is not exactly R2O3, though that's the closest thing I can see, and it's very acid, so where do I put it? ...etc.), I'm all for this. Neither method tells the whole story, but together they provide a more solid basis for dealing with a rather slippery subject.
I have been having a truly jolly time these last few days, tweaking the British formulations over into US ingredients. I don't trust my results yet, because I detect certain discrepancies, but I'm working on it. (For example, I detected an incorrect formula weight for Red Iron Oxide in my glaze program when I built a recipe that calculated to contain a smaller percentage of Fe2O3 than I was putting in, something I could never have detected by looking at the usual Seger-style numbers. The error was my own, but has now been expunged. I had to recalculate dozens of glazes, argh.)
I still haven't made holes in the lugs of the teapot, and I still haven't put the lugs onto the pot, but I may try to get by the hardware store tomorrow and look for a suitable tool for making round holes in mush.
The other night I went to the pottery and combined almost all of my "slop bucket" stoneware, after which I tried to throw a platter. Hah. As usual, I got just about to the end, whereupon the platter flopped. Too bad, too -- it was a nice big one. I am not easily deterred, though: I just folded it up, kneaded the clay again, and threw a 17" bowl. I figured I'd be back in a couple days to clean it up, and I didn't want to distort it, so I didn't wrap it.
What I forgot, in the heat of the moment, was that our concert was two days later, and there was zip chance that I'd make it back. I then failed to make it back the next day, so I didn't manage to reach it until yesterday (Saturday) morning, by which time it was developing a drying crack. I did the stupid thing: carved out a thin layer of the inside bottom to make some clay, wetted it down, and sorta re-threw the top layer of the inside of the bottom. Then I put some plastic wrap in the bowl, placed a very wet sponge on the plastic wrap, and stuck the whole thing inside a trashbag, which I folded shut to keep the water from whistling off into the ether.
I was at Glen Echo for a short time again today, but neglected to check this assembly or to add water to the sponge. I just hope I can get down there on Tuesday to make sure it's all stable, because after that I go away for a week. I'm going to a wonderful place (Seattle) to do Good Works, see friends, and have fun; but I'm still griped about leaving all this work in progress. Sigh. (Besides, on Sunday they'll probably empty the kiln, and I want to see how my glaze tests work!)
The big bowl is easily the largest thing I've ever
thrown, and because I lack upper-body strength I had a
tough time centering the clay the second time I threw
it. Good exercise, though, and another milestone along
the path of learning to throw. (...And yes, I'll be
somewhat put out if it cracks through, especially now
that I've put extra effort into trying stupidly to fix
it.)
More as it happens...
Pseudo-mailto: jon [at] bazilians [put it here] org
Last modified: Mon Jan 29 20:17:03 PST 2001