We fired the wood fired raku kiln yesterday with just a few pots. I wanted to test some clay and glazes, so had pots made from 4 different clays, and tested about 4 different glazes as well. I lit the kiln at 9.10 am, and had the firing all over with and the pots out of the kiln exactly 3 hours later. The firing was to about 1050 Centigrade.
I have included 3 photos of the nicest pots that came out of the firing. The first pot has a simple glaze inside and out of alkaline fritt 4110 70 parts by weight, 18 parts china clay, and 2 parts bentonite. This has another copper bearing glaze brushed over it for decoration. I have used this copper bearing glaze by itself on the second pot, the recipe is as follows: Alkaline fritt 4110 75, China Clay 10, Silica 10, Titanium oxide 4, bentonite 1, copper carbonate 5.
The lidded jar has the simple glaze that the first pot had with the addition of some red iron oxide, about 5 percent. Wax resist patterns were painted onto this, and then the copper bearing glaze was poured over the outside and brushed on the lid.
I find that alkaline fritt 4110 is a very useful one for raku and for earthenware glazes. All that is required for a simple glaze is the addition of some china clay or some ball clay. Glaze fit can be improved by the addition of extra silica. I usually add 1 to 2 parts of bentonite to my glazes, this helps prevent the glaze from forming a rock like lump in the bottom of the glaze bucket, and also makes the surface of the glaze less powdery and delicate when it is on the pot before it is fired.
Just a quick post this as there are lots of things to do today, including fixing 2 holes in the living room floor, sorting out my studio, giving a lesson, and opening our gallery this afternoon....!
Sorry my glaze testing number 2 post hasn't quite happened yet.
I fired some stoneware chun glazed bowls in my electric kiln a few days ago, here are photos of one of them.
Following this should be a video of the wood fired raku kiln firing.
Firing The Kiln
When firing this kiln I establish a small fire in the ash pit and warm the kiln for about half an hour. At first I keep the fire box door open to allow cooling air through.
Once the kiln and pots are warm I close the fire box door and let the temperature climb to about 400 degrees centigrade. At this point I have a good bed of hot ashes in the ash pit and I am able to start a fire in the fire box above the grate.
The temperature climbs rapidly.
You will notice that I continue to occasionally stoke the ash pit as well as the fire box. This is to ensure good hot embers there to pre-heat the air going into the firebox. Later in the firing everything is so hot that this is no longer necessary.
I unload the kiln when the glazes are really shiny, this is at about 1050 degrees.
The pots are placed on shredded newspaper on a clear area that has a bed of ash and charcoal from previous firings.
Tin cans containing more shredded paper are placed over the smallest pots.
Larger pots are placed in bins, with tops sealed with damp newspaper, and a kiln shelf placed on top to stop the air getting in.
I allowed the pots to cool for two hours before looking at them.