J’accuse: Frit 3134

Remember the Evil Clear glaze? The nasty, awful, no good clear that wasn’t clear, ran like crazy, and ruined an entire kiln load of pots? I re-threw everything. I bisqued it. I mixed up a shiny new batch of clear, double- and triple-checking the ingredients and the math.

And the same damn thing happened.

I suspect the tub of frit 3124 in the studio’s glaze kitchen is mis-labelled. Or rather, correctly labelled but containing the wrong frit.[1]

Alexis from up the road (who also suspects it’s a mixup with the frit) gave me some of her 3124 to test. There’s a test tile in the kiln now, and I should know by Thursday what’s up. On the off chance it’s not the frit, I can start fiddling with the EPK and the silica, but I strongly suspect it’s the frit.

[1] On the up side, at least now I know the fuck-up wasn’t me being inattentive about my ingredients.

The 21st Century Glaze Project

So here’s a cool place to check out: Glaze21 exists. It’s a glaze archive, which you can find here and there on the interwebs, but this one’s better in three important respects:

1- It’s got more people sending in submissions than the other ones, which means more recipes, more testing, and much more commentary on success/failure/issues.

2- It’s searchable!

3- The plan is to eventually have colour photos of each glaze, on various clays.

I am enjoying having a poke through it.

Moar Tests

Mixed up a few test tiles yesterday. I’m hunting for two glaze bases I can use over cream or white clays, one variegated, and one which will take well to being turned pink. And hopefully also be clear, or clearish.[1]

I know from this article over on Digital Fire and this batch of test tiles that it’s possible to do it with Mason Stains. I’ve got two tests mixed up of my own, using the fourth recipe variation without cornwall stone (one with talc, and one without), to see if I might have any luck getting a nice colour with tin and chrome instead f the commercial stains.

I also mixed up a glaze called “Powder Box Pink”, which elusive internet rumour has it came from a book that was featured in Ceramics Monthly in some issue or other, where the author talked about getting pinks without having to use chrome. I have one tile for the recipe as written, and one with rutile, just for shits and giggles.

Oh, and I also mixed up a glaze I found one day in the studio notebook. It’s called “Surf”, and predates my involvement with the place, but when i asked one of the oldtimers about it she got all misty-eyed and nostalgic, so I want to see what it looks like. I switched the colourants around so it should come out looking sort of turquoisey instead of dark blue, but otherwise left the recipe as it was.

[1] The plan is to mix up a bunch of buckets–one pink, one apple green, one purple, and one bright blue–and use them on the Just For Fun mugs I made back in January.

Google Requests: The Sequel Strikes Back

This week’s google request is “aqua glazes”.

Well, I’m not going to list off a bunch of recipes, because that would make for an awful lot of typing, and I’m doing this on the last few minutes of my lunch break. But I can give you some guidelines, assuming you’re firing oxidation.

1. Pick a base recipe you like, or that looks interesting. Google “sankey glaze database” or “clayart archives” (or just follow the links in the sidebar) for more recipes than you can shake a stirstick at. Or flip through some old pottery magazines; most of them have a glaze recipe section. (If you’re a CCNL member, you have an entire library of them you can access, in person or by mail.)

2. If the glaze is acidic, adding 1-2% copper carbonate should make it some shade of aqua. If not, try 1-3% copper carbonate and a teeeeny pinch of cobalt carbonate… say, 0,1-05%. Don’t overdo the cobalt; it’s strong stuff, and it’s easy to go from aqua to true blue.

There. That’s really all you need to know.

Testing, testing….

Mixed up some tests for the teapots this evening. Glaze tests are small batches (usually 100 grams plus colourants) of whatever recipe you’re planning on testing. You mix up all your minerals, add them to water, sieve the whole shebang a few times to get a homogenous mix, dip a small bisqued tile in your new sludge, and fire the tile to see what the heck the recipe looks like when *you* mix it up (because, thanks to the wonderfully varied natures of mineral deposits and tap water, the exact mix of moleclues is never the same from one studio to the next, and what the other guy says is a varied green/brown glaze breaking blue over edges could, for you, come out a plain muddy mess breaking muddy).

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I’m playing with two of the recipes I came up with from the glaze chemistry course a few months ago.

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The first one is mostly good (that particular tile there is a chrome/tin mix that came out a nice pale lavender colour, and there’s another test tile with nickel that came out almost lime green), but I want to see how it behaves over a clear glaze. I’m hoping it’ll change the texture a little–if not, I’ll have to fiddle with fluxes and refractories and try to make it melt more smoothly–and I also want to see if there’s a colour difference.

The second one is my favourite in terms of colour and feel (soooo glossy and smooth), but it started developing cracks the second it was out of the kiln. This is a sign that the glaze and the clay don’t have a good “fit”–they are expanding and contracting with temperature and humidity changes, but not at the same rate. The stress caused by the different expansion rates causes crazing. All pottery crazes with time, especially clear glazes, but it’s considered bad technique to have something craze this quickly[1]. I added some silica to the recipe, which should reduce the crazing and, as a happy side effect, reduce the epic runniness of the glaze[2]. I’m also layering this one over clear and, just for shits and giggles, doing an extra tile to see what we get with chrome and tin as colourants instead of the original copper carbonate. I’m hoping for pink or purple.

[1] Unless of course you *want* that look, like with crackle or crystalline glazes. But I don’t.

[2] Runny glazes are prone to dripping or, in bad cases, sticking their pots to the kiln shelf. Sometimes, chisels and angle grinders are involved in trying to save the kiln shelf (the pot is usually a lost cause). It’s bad.

Pics

Got a new card reader, so you get a picspam post today.

First, that third cephalopot glaze test is out of the kiln. Here’s the three of them together:

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I like the one on the end the most. May bring the fluxes back down a wee bit, though; it’s a tad runny.

And here are those tea bowls, all finished:

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I didn’t have my notebook with me when I made them, and accidentally used a third less clay than usual. They came out the same size, though, or very near… I knew my throwing skills had improved over the last year, but I didn’t think there was *that* much of a difference. Cripes.

The hoya in the studio is in bloom. It’s the same cultivar as my grandmother’s, who got hers from a cutting off her mother’s plant, which started as a cutting from the hoya in the garden in Indonesia. The smell always reminds me of my Oma.

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Aaaaand, last but not least, cephalopot cream and sugar set!

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Might even out the size of the tentacles in later incarnations. Or I might just leave ’em all different. We’ll see.