I have received some surprise when I mention that my floor sand melts during firings. It really does, but it will only become glassy where it is thin enough to spread out on something harder, like the bricks I pointed out in my previous post. Where the sand is thick, only the top layer will melt.
Here is an example from the sixth firing, one of the most beautiful firings and the most disastrous due to multi-level shelf collapsing.
Full size image.
This piece was just back of the firebox — a band of black koge can be seen in the front of the image. The rest of the images from the sixth firing are posted on this site, but the location is pretty buried — I should add them to the photogallery.
Anyway, Furutani’s kiln design has no trouble melting sand. In fact, it is beginning to dawn on me that I will have to work harder to keep firing temperatures down a bit, as I believe I’ve been overfiring to some degree.
I video taped a little during the sixth firing, imported the tape into my laptop, and then let it languish for the last five months. I’ve been wanting to recover the 15gb of hard drive space it took up, and I was finally bored enough to stay up all night, cut it into little bits, and paste together a four minute clip.
You’ll see the anagama being fed, make a tiny steam tornado, and breathe fire. When the fire is pouring out the chimney, it’s like a river of bright water rushing over rapids. I could watch that almost endlessly.
One part may need a little explaining: about midway through the video, and at about the hottest temperature during the firing, I take out a “pull”. A “pull” is a piece specifically made to be pulled from the kiln so that the amount of glaze build-up can be evaluated. Pulls are crucial because the end of the anagama firing is determined by how well the pieces have developed ash glaze. Temperature is obviously a factor, but cones typically flatten out by the end of the first day of the three to four day wood firing period — where cones really fall down, is that they say nothing about the level of glaze build-up. By loading a few pulls, the glaze level can be checked quite thoroughly.
Without further ado, here are links to the video. Note: quicktime format; both are the same content but the 20mb clip is better quality, though a somewhat hefty download. I’d suggest doing a “save as” on the link as it might take five minutes or so even with a broadband connection.
~6mb video clip, really low quality
~20mb video clip, acceptable quality
