All fired up

This is another thing I’ve been up to lately.

Raku bowls

This is raku.

Raku bowls

Recently, while I had my light tent set up taking the jewelry a couple of posts back, I took these too.

Raku bowls

The shiny-but-dark is tricky to photograph, especially with the cell phone.

Raku bowls

I’m totally in love with this style of pottery. There are lots of styles of pottery and glaze techniques. Raku originates in Japan. Part of the glazes on mine contain a lot of copper, creating a very distinctive look, although there are other completely different glazes as well.

Raku bowls

The main hallmarks are that raku is typically fired at lower temperatures (1800 degrees) usually in a gas kiln (not electric) for a much shorter time. While it is glowing hot, it is pulled from the kiln and dropped into an awaiting metal container filled with combustible material. The heat of the piece immediately bursts it into flames. A lid is slapped on, the flame continues to burn inside, using up the oxygen, creating an oxygen reduction atmosphere. Sometimes after the flames are gone and it’s cooled slightly, but still very hot, it might be plunged into water.

All the temperature changes and thermal shocks, on purpose, produce a crazing in the glaze. The burning material will turn any cracks or unglazed areas black.

Diz and buttons

Sometimes the combination of all the factors can result in brilliant colors.

The oxygen reduction atmosphere and other factors react with the glazes, like with the copper-containing ones, it will create utterly unique and unpredictable results.

Diz and buttons

Raku is typically considered decorative rather than food-safe. One, there may be components in the glazes that wouldn’t be food-safe. Since it’s only fired to 1800 or so, the clay body doesn’t reach a state of vitrification (tiny little glass crystals form throughout), which is what makes clay hard and non-porous. Also, because of the thermal shocks and lack of vitrification, the pieces can be a little more fragile.

Raku process 1

At the beginning of the process, we use paint brushes to apply the glaze, usually several coats. Like most ceramic glazes, the color of the glaze can look nothing like the finished results. The bucket with the black goop is the one that made all the pretty copper colors.

Raku process 1

Here, we’re waiting for the glazes to dry thoroughly. Trying to help it along with a hair-dryer. In the picture, the spiky thing that looks like a denuded tree has high-temperature wire poking out of it and is what I have my buttons hanging on. Glaze can’t be on the bottom of things or when it melts it will glue itself to the kiln shelf. Not good. Things like beads can be suspended on high-temp wire to get around that issue.

Raku process 1

Once the glaze is dry, pieces are placed into the kiln to start firing. While waiting for the glaze to get hot enough and start to change, we prepare the cans the hot pieces will go into. We pick metal cans and tins a little larger than the piece, then line those with shredded newspaper and some sawdust. Anything combustible, but these are common. Pine needles can be used, whatever. That can be an art unto itself. We also prepare a lid, ultimately wrapped in wet newspaper. It has to be wet so that it won’t catch fire because you want it to make a tight seal when the oxygen starts burning away.

Raku process 1

Here, after a peek, the glazes look ready, so it’s time to start pulling the pieces. It’s a three person job. In the picture, on the left, is my instructor Barrie. If you’ll notice, she’s got on long gloves (we all do), and is using long iron tongs to reach into the kiln to pick up a piece and bring it out. It’s very hot, even with all the protection. These pictures are from when I did it last, but after handling the raku firing some people did today (we do once a month or so), she looked like she had a sunburn.

Another person is working the sliding kiln door so that it’s not open too long and loses a minimum of heat. It’s possible with only two people, but it’s easier to work more quickly with someone working the door. The idea is to not lose too much heat from the kiln while the door is open, or let the piece cool too much before it is put in the combustibles. Although some let it cool a bit…that whole thermal shock thing, more crazing in the glaze.

Standing ready, one of the students has the lid wrapped in layers of wet newspaper ready to cover the cannister once the piece is in.

Raku process 1

In this picture you can see the very good reason for gloves.

Raku process 2

Once the lid is on, holding it all tightly together, the cannister is moved away from the work area so it’s not in the way and we don’t inhale the clouds of smoke it creates. A brick is put on top as a weight to keep a good seal. The smoke eventually dies down, but I always smell like I’ve been around a campfire. Not unpleasant unless I accidentally get in a cloud of it.

Raku process 2

We wait for the cannisters to cool and once we can handle the pottery bare-handed, we get to open things up and see what happened. That is totally the best part! It’s so neat, like unwrapping a gift to see what you got.

Here’s some of my little bowls, buttons and the diz laid out. Awesome! Love some of the effects I got. I keep notes on what I did, but by its nature, raku is hard to reproduce. But that is what makes it special.

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