Saturday, June 27, 2015

A Kiln Mystery

 I fired 2 of these mugs with the same glaze  --  T's green  --  in the same firing in the ECC school kiln. Same clay, same glaze, same firing. Should come out the same, right? Ha, why should it? It depends what the glaze is made of; some glazes are very invariant, some change with thickness of application, temperature, amount of reduction in the firing, and certainly over different clays.

In this case the kiln is not under perfect control; it's a fairly large, hard used, gas kiln in a communal studio, loaded by a varying group of people. The temperature of firing varies a fair amount from top to bottom, the reduction is variable and spotty, and I do not know the kiln well enough to predict what will happen to a pot in a particular place in the kiln. I did not load these cups into the kiln. A setup for mysteries.

Here is the second cup. Same...

Obviously they were not loaded together. This is what that glaze does at a slightly higher temperature: a darker color, glossy, translucent, and with those great crystal speckles. 

Is one "right"? I was aiming for the second. I do like both, though not as a set.  And I actually like it that things are somewhat out of control  -- after the initial shock.

Saturday, June 13, 2015

Itching to Open the Kiln

The kiln was cooling, overnight and in the morning, with a load of newly glazed and fired pots. Do you know how hard it is to leave it alone, even though it is really too hot to handle?

This is the point where process becomes product, hope is realized or lost, the invisible changes in the firing can be seen. Potters tend to be extravagant, mystical, a bit wild about glaze firing and the marvelous transformations that happen in it. It's the last step in the rather slow affair of making pots, so the time of success or failure.

And so opening the kiln after a glaze firing is a big deal. Some potters make it a party or an event to share with customers. I do it privately, to absorb what has happened with my latest pots before anybody else sees them. By noon the kiln really was cool enough to empty, after several pretenses in that direction. First I propped he lid up for a few hours, checked it too often, then opened the door and waited some more, then just had to look below the visible top shelf.

That's the first view, the top shelf in my rather small kiln. Looks good so far. But what's down under there? It's a treasure hunt, every time.

Whew, that big platter survived. But the people who asked for it want the same colors as this plate:

Not close. I made a guess, that the colored slips used on both would come out the same color in firings at two different temperatures, and one oxidation, one reduction firing. I think the slips (liquid clay) were colored with stains, which tend to be fairly uniform. They do have top temperatures for keeping their color. I've got another platter to fire at a school, the same way the plate was fired, and hope it will work. Never make just one for an order; "things" happen. So why fire the platter at home? It's bigger than the space on a kiln shelf in the school kiln. The other platter is oval and barely fits there.

These came out fine, just enough thinning of the glaze on the top edges to emphasize the shapes a bit. I like it.

This one was refired with some glaze added to cover, I hoped, a couple of raw spots on the bottom. It sort of worked, not great.But the colors!

Hmmm. What an odd color.Think I'll try again.

Ah, yes. A new glaze I've only seen so far on tiny test pieces. I really like it.

Yeah, but thin glaze. Why? Maybe I'll refire with more glaze. I feel fairly free to do that, as my kiln doesn't use much electricity.

That's a lot better than before, a refired piece with more glaze on it.

So, as usual, a mix of more and less successful pieces. I learn this time to pay better attention to glaze thickness.

The treasure hunt went fine. The mystery continues, the surprises kept coming, and there are some usable new pots. Nothing fabulous this time. The red glaze is promising in it's variety of shade. Onward!