Here I am again firing some clay pots and tiles. Some pots are refired to try to put glaze on the sides that didnt get any last time. I think I may have gotten the kiln a bit hotter this time from the color of the glow. Took me about 8 hrs because of the cool wind early on. I also used alot more salt at the end this time.
I had a few tiles and one vase from the last firing that had really good glaze coverage this time. The rest will need to go back in again to get glazed fully. My crummy kiln is probably the main cause of the partial glazing.
Here are some results to share with all of you!
The tile warped because I had it leaning against a brick.
I had a few tiles and one vase from the last firing that had really good glaze coverage this time. The rest will need to go back in again to get glazed fully. My crummy kiln is probably the main cause of the partial glazing.
Here are some results to share with all of you!
I wonder why red clay turns almost black when salt glazed. Is it the heat or carbon from reduction firing.
The tile warped because I had it leaning against a brick.
Here are the pots that didnt get a full glaze effect from the salt.
They will have to go back in for a second try. I will place them in different locations of the kiln to even the glaze out. The back of the chamber seems to get the best glazing effect. Must be the way the gasses are flowing to the chimney flue.
You should have a crack at making those red andl black pots that the Egyptians had. The ones that have black around the rim.
ReplyDeleteFazer: Thats an interesting idea. I will take a look.
ReplyDeleteHi Richard,
ReplyDeleteReally impressed to see your experiments with salt firing. From the photos, it looks like you are acheiving quite high temperatures in the kiln, wonderful incandescent glowing pots (I wonder what the temperature actually is...? you really must get some cones in there!). I have no expertise in salt glazing, but a couple of things spring to mind regarding coverage. Most salt glaze potters fire well above 1200 degrees Centigrade (2192 F.) and begin salting around 1240 Centigrade (2264 F.). I suspect that the salt needs these temperatures to really turn into gas quickly and thoroughly, below that makes things more difficult, but not impossible. Many also report using their chimney dampers to restrict flow out of the chamber whilst salting, or to make the atmosphere in the chamber turbulant (by pulling dampers in and out). It occurs to me that at the quite possibly lower temperatures that you are trying to salt at, you probably need to hold the gasses from the salting in the chamber as long as you can, in order to allow time for the salt to completely break down and liberate all its goodies, before they go up the chimney. The other thing is that many salt glaze potters report that the first few firings of a salt kiln usually are not very good. Things improve as the salt glazes the bricks of the kiln through repeated firings. This build up of salt glaze in the kiln volitizes at high temperatures and helps coat the pots that are fired in it.
The blackness of the red clay is interesting. Certainly heat has something to do with it (it looks really hot in there for a red clay), but reduction atmosphere and fluxing of the surface of the clay is probably the real cause. The salt vapours will be fluxing the silica in the clay, and the high iron oxide levels in the red clay will be doing their best to form a tenmoko style glaze! Any iron oxide in the clay will be loosing oxygen atoms like mad in the reduction atmosphere and be turning the iron from a red to black state. Wonderful stuff!