Category Archives: kiln

Rain, rain, GO AWAY…. REALLY!

It has been raining cats and dogs since this morning, and we must have gotten about 8 inches in as many hours. Unreal. It is the first time the water has risen in my kiln to a level that would affect pots if they were loaded into the first chamber. In the past it has always stopped short of the front floor but today it was a couple of inches deep in the front floor area.

At least I had good weather yesterday and into early this morning for firing the gas kiln. Turned off the kiln at around 5 am (fired for 18 hours) and when I woke up at 6, it was pouring. Later in the day, I peeked into the kiln when it was still around 700C. Snapped a couple of pictures, with and w/o the flash. The first glance doesn’t look too good. Ame yu was a bit too thin, I think, but won’t know for sure until I open the kiln up completely and have a good look. One thing I am happy about is that the new clay blend I was testing seems to have stayed together nicely, no bad slumping (a little slumping, I like).

The Final Coat part II

Got two more tons of cob mix delivered yesterday morning and finished up the top coat on the kiln. Lots of mix left over for filling cracks later, and also for finishing up the pizza oven next week.

One thing I was really happy about was not coming across any dead frogs in the cob, like the last load.

As you can see, great care has been taken to keep the front crack free. I’ve been paddling  and burnishing it in a vain effort to keep it smooth.

You would think there is no real practical reason to keep the surface smooth, but the way it was explained to me, this is actually quite important, because during firing when the kiln leaves orbit and begins re-entry into the Ceramisphere, the temperatures and stresses exerted are phenomenal. Any crack or weak spot in the top coat could lead to catastrophic failure in the kiln structure. ; )

The Koi Pond

My apologies if you are getting sick of these water pictures. Whenever it rains and fills up, I for some reason am compelled to take a picture and post it. Some sort of weird compulsion I guess.

Anyway, I had an epiphany after the latest rain (we are into rainy season here now, with a vengeance). Why not use the kiln area as a koi pond when not firing? Not only would it likely be the first kiln in the world to also double as a water feature in the yard, but visitors could also enjoy the koi, and perhaps would even pay for those little packs of koi food, like at the zoo. Genius, no? OK, well, maybe not.

Still here’s that picture I am compelled to post.

With the primary air dampers closed, couldn’t the area under the grates be used as a separate enclosure for raising the fry?

The Final Coat

The mud that I ordered came on Monday, and even though the kiln is still warm, I’ve started applying it. Actually, it really helps it harden faster and stay in place. It will crack pretty badly but it would anyway, and I plan to go back later and fill in cracks and joints later anyway. What you see here is one ton of cob, which is composed of unrefined red mountain clay, decomposed granite sand, and straw. I don’t know the proportions, but it shrinks about 3% from wet to dry.

Now that the first ton is used up, I need to order one more, and that should be enough to finish the job, then have leftovers for crack mending and a finishing coat, plus enough to insulate the new pizza oven that we are building from leftover kiln bricks.

While working this morning my twisted mind came up with this, you may be familiar with a slightly different version:

“I held the spade in trembling hands
Prepared to slap it on but just then the phone rang
I never had the nerve to add the final….    coat. “

I know, really bad…. Sorry.

The maiden voyage of the Uber-Blend 5000 Turbo

 I acquired this piece of machinery, the Uber Blend 5000 Turbo, from a kindergarten that had used it for mixing large batches of powdered milk. It is basically just a very heavy motor suspended beneath a large reservoir, driving some wicked looking 4 inch wide mixer blades. It is so heavy that it needs its own frame to support it and stand it up. When mixing is done, the entire reservoir can be tipped down to decant the contents.

I’ve been doing lots of glazing this last week, and decided at the last minute to test a new glaze in the upcoming firing. This glaze is basically just stamped feldspar and ash, in a 9 to 1 ratio. Anyway, mixing up this stamped feldspar is always a time consuming, tiring affair, because it comes in cakes straight from the filter press, and is like a stiff clay. Getting this to melt in water is tough. If you let it dry completely, as I have started doing, it gets rock hard, but is easy to break into smaller chunks. I’d been slaking these small chunks in water over a period of days or weeks to prepare it for thorough blending with a drill mixer, but this time I had the Uber-Blend 5000 Turbo!

Here are some of the chunks of Taishu feldspar. These were the smaller ones, measuring a couple of cm across. The largest chunks were up to about 7cm.

The Uber-Blend 5000 Turbo, in all of its sleek elegance. It is an absolute chick-magnet. With this baby parked in the studio, who needs a Lamborghini?

This is 9kg of spar and 1kg of ash turned almost instantly to smooth, silky glaze, requiring NO screening. There were a few tiny lumps left after the initial 30 seconds, an additional 5 minutes of uber blending and they were history too…

And in conclusion:  IN YER FACE, Magic Bullet!

Happy potting everyone.

Some more improvements

The first firing showed some of the flaws in the stoke hole cover for the front of the kiln, the first being not enough extra overlap around the edges, and the second more dramatic one being the loosening of the frame in the heat, causing the cover to fall out of its frame in the middle of the firing, which was an exciting event.

I cast a new, larger cover for the front stoke, and moved the original to the rear chamber stoke hole, where it is looking quite sharp and happy. The implementation of the frame for the front stoke was done a bit differently, just to see how it plays. I think it will be more stable, balanced and less likely to come apart during firing. At some point, I’d like to do a welded door, but for now this will work.

Here is the cover assembly. I had to drill holes for the rods, but it allows for the angle iron to be oriented across the center line of the slab.

 Detail of the angle iron, threaded rod, and shims. My plan is that the shims  allow for the angle iron to be tightened to a slight bow, and hence to be in a state of tension, so that when the frame heats up in the firing, there may/will be a loss of tension, but the frame will remain tight and secure around the slab.

 Here it is hanging in place. Twisted 2.1mm stainless iwire on the cover assembly. 3.2mm stainless wire twisted around another threaded rod, connected from the overhead beam. In the first firing there was no discernible softening or stretch in the wire (2.1mm) from the heat, so this 3.2mm wire should last a good long time.

The next improvement is by mother nature, who is giving us our first really good bunch of wisteria blossoms:

The coverage is a little sparse, but with a few good prunings over the next couple of years, this little gal should fill in nicely. I’ll post pictures again when the blossoms are in full bloom.