Glaze, glass, clothes for pots, clothes make the man.
Like clay, glazes are in theory pretty straightforward: a stone that, when heated up high enough, melts into a glass. The simplest would be using 100% silica – sand – but silica melts only at 1400°C, and most pottery is fired between 1000 and 1300°C. So we need to add something to the silica to make it melt earlier.
So oh my how many different ways there are to make (and to fail at making) a glaze.
You can buy pre-mixed glazes from suppliers, it’ll be pure and predictable but then you’re paying for their work – you don’t know exactly what’s in the glaze – you can’t modify it for your purposes – it’s usually rather boring.
You can mix your own glazes from raw ingredients, it’ll be yours but then all the successes or failures fall on you. Does it stick to the pot, or flake off? Is it completely melted, or still a little rough? Does it have blisters or pinholes, or is it smooth across? Are those cracks supposed to be there? Does it scratch when you’re cutting through that steak? Oh, and: is it the right color?
So I’m trying to get better. So last month I went off to spend a week learning about glazes. The teacher, Markus Böhm, is if anything interested in formulating glazes through empirical methods. Way back when the Japanese apprentices might learn “take one scoop of this, two of that, heat it up until the fire burns this&/that color, and it’ll turn out”. That did work, and still works, but those there potters are building on centuries and generations of experience. Chemical analyses and computer programs can make the learning process a bit faster.
So we (six of us in total, a mix of hobbyists and career potters, all wanting to make a better glaze needn’t be said) used chemical analyses and computer programs and from about 6 base ingredients made over 1.400 different variations of ceramic glazes. A little bit more of this ingredient, or a little bit more of that, and you’ll get a range of results from the utterly unusable to the cosmic.
The whole thing happened at the International Ceramics Studio, this delightful former porcelain factory smack dab in the middle of Kecskemét, Hungary that’s been turned into a state-then-city-run base for potters of all walks to come and make and fire their work.
And so we made and glazed and fired our work. 2 days of theory about glazes, 2 days of practice making the glazes, 2 days to fire and open the kiln.
And then when we opened the kiln: results. What we learned about glazes, the mixtures we made, the ones we thought would succeed or fail; all laid bare before us.
I came away with knowledge, firstly, but also a few cups. Some of them are up for sale at my Etsy.