Thursday, July 09, 2009

Dirty Potter

I guess that I have been absent for most of the week. Sorry about that , but I have been playing in the mud. I have, for the last few days, become a dirty potter.

I have been taking part in an EdVentures workshop. As some of you may have read earlier, I am teaching a workshop in Temari Balls this summer as part of a workshop series . And since Monday, I have been taking a Raku Pottery Workshop. Monday, Tuesday, and Wednesday were devoted to making things to fire. They were then bisqued so that we could glaze them and then glaze fire them in the raku kiln. Bisquing is basically cooking the pots so that some of the chemicals are driven off and the pot becomes hard enough to handle without fear of breaking.

So sorry for no photos of the actual making of the pots. I spent most of the time with my hands (and various other parts of me) covered in clay. Clay and camera don't mix, and ever time I thought of taking pictures, I would think "I'll take pictures as soon as I wash my hands". Unfortunately, washed hands were quickly followed by something else equally dirty. So, sorry. no pictures of any sort of production.

Here is the set up for out raku firing. Normally, pottery is fired to a bisque then glazed and fired to what ever temperature the clay body can stand before melting. This process takes a couple of days. In raku, the clay is bisqued, then glazed and fired quickly. In fact, it takes about 45 minutes from the time that the pots get put into the kiln until they are ready to be taken out. It is TOTALLY AWESOME!

Here is the set up that we have. We first put the kiln in place (which you can't see here) then put the metal garbage cans at the ready. The garbage cans have a layer of sawdust in the bottom to give a good surface for the pots to sit on once they come out of the kiln.
Here are the different glazes that we are using. There are 11 different ones. So many possibilities! Erica, one of my class mates, is contemplating the possibilities.

Here is the kiln. It is a gas fired kiln that, once warmed up, takes about 40 to 45 minutes to reach about 920 C. We gradually increase the temperature over the time by turning up the burner.
This is the first firing in the kiln. It is easy to load because the kiln is cold. After the initial firing, the kiln is hot (oh baby so HOT) and it is a little more challenging to load it.

Here you see me and Shaun getting ready to unload. We have in protective leather jackets and aprons. The heat is intense. By the end of the first unloading and reloading, my face was beet red and stayed that way for about 40 minutes. After that, I used a face shield. As I said to someone, I am NOT a "real man".
The caution tape is to keep the general public from wandering in and burning themselves or getting in the way.
The pots come out of the kiln and go into the sawdust bins. After a few pots get put in, some newspaper gets dropped in and because of the heat of the post starts to burn. This causes what is called reduction. The burning paper causes the oxygen in the garbage can to burn out and the oxygen molecules that are in the various glazes start to be leached out by the oxygen deprived environment and a shift in colour occurs.
The lids are put back on the bins after each pot is put in it to keep the oxygen low.
Here are a few of the test pieces that some of the students have done just after being put in the bin.

We had a lot of interesting observers. There were periods of waiting......and waiting.....and checking of the kiln......and then suddenly a flurry of activity.

After the kiln was unloaded, the small pieces of fire brick that each pot was sitting on had to be unloaded and then new fire brick put on the shelves and on each piece of brick, a new pot was placed. It was very challenging to load the kiln. it radiated heat and so each fire brick needs to be put in with the long tongs (relatively easy) and then a new pot needs to be gently placed on each piece of fire brick with the tongs (not so easy). The pots can not be too close to the edge, nor can they be touching and you really don't want the pots in any place that is in a "hot spot", which is where the flames lick along sides of the kiln and the pots and makes a localized area where the temperature is hotter. The problem with this is that the glazes have all been tweaked to melt at about the same temperature ( thank you Peter!) and hot spots will melt the glaze in that area sooner. Melted glaze is molten glass and molten glass runs. Which can create one hell of a mess.

After the pots have sat in the sawdust and newsprint bins for about 15 minutes, it is time to quench them. The tongs are again used to lift the pots from the bins and gently placed into vats of water.

After a few minutes the pots are then cool enough to handle and the black from the smoke is scrubbed off. And there you have it! Raku pots!

And by the end of the day, I was totally bagged. This was just about the first day that we have had all summer that actually felt like a summer day. The sun was shining and really really hot. When we weren't "on duty" ( we each took turns loading and unloading the kiln as well as being the one who watched the kiln to make sure that it didn't over fire and run glaze all over the place) we would duck back inside to glaze a few more pots or grab a drink of water.
After we fired the last kiln of the day, most of us went out for a beer. And I meant to take a picture but... I have to admit that once that tall frosty beer was set in front of me, thoughts of pictures flew away.

Tomorrow, Day two of firing and .... my pots.
But be warned, it will be late in the day or maybe not even until Saturday. Tomorrow, we will fire until we are done. No matter now late that may be.

Oh my.


Julia said...

Raku sounds interesting. Glad that you are enjoying it.

One question, do they use kiln wash in a Raku kiln and on the bricks that supports the pieces of pottery?

jackie said...

No kiln wash. Just the little fire bricks. If any glaze gets on the bricks, it just gets chipped off when it cools off.
Teh reason for the small bricks is so that the cool pots don't get a huge shock from being put of a hot shelf. Raku clay is really shock resistant but even it has its limits!