Category Archives: tools

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 new pizza oven

Today we got to work on the actual oven finally. We did the base a few weeks back and have been waiting for the rain to abate. We started out pretty straight with our chisel split bricks, the top 20% though gets a bit dodgy, but we hammered the keys in and it is standing on its own, if not very pretty. Over what you see here will be a 5″ thick layer of mud and straw, to seal everything up and add some mass to soak up heat.

The cooking surface is hard castable. Under that is hard fire brick, under which is soft insulating castable, under which are empty beer and sake bottles. The base is a mortared brick cylinder filled with a ‘lasagna’ layered matrix of large and small rocks, and concrete. We needed somewhere to get rid of all the rocks that had surfaced in our landscaping projects, and this got rid of  more than half.

A few strips of bamboo make a quick and dirty arch support for the edges.

Not too bad for a few hour’s work. The bricks are all scavenged, and the dome bricks are wedges cut in half. Arch brick for the door. Left over wedge scraps stuffed in at the apex with mud to fill gaps. The same top coat I used for the big wood kiln will work great for this oven. Inside diameter of oven is 70cm, and inside height is about 46cm. Door height is 63% of the inside height.

The advantage of having the big thick mud exterior layer is that later after a few firings, if the brick dome starts to fall in, the mud dome will remain. Not only that, the interior of the oven will actually get bigger….. : )

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.

Loading it up…

I started loading the kiln on Sunday, but didn’t get very far. By Monday evening the rear setting was finally finished. For some reason the rear setting is time consuming. Today (tues) I started the middle setting and got it about half finished in 2 hours.

Here is the rear setting going in:
Fairly low temp glazes at the bottom rear. That rear bag wall has holes along the bottom for a bit of flow, but I want to see what I get there as far as temp and reduction with limited flow. Most of the rear setting stuff will mature at Orton cone 6-8.

 The plates on the floor should get nice and covered in embers. The top left, behind the beer mugs, has another large jar that is not very visible in the picture.

It rained all night monday night and this is what greeted me in the morning:
The water missed the mattress by about one cm. To get an idea of the depth, look on the left side and you can see the shovel handle.

 There is a black spot on the blue mattress and if you look closely you can see it is a frog. Unfortunately, he is dead. One of the neighborhood cats has taken to having his midnight snacks in my kiln. I wish he/she would clean up after eating…

 All pumped out now, but with the continuing rain, I have to turn on the pump frequently. I leave my sandals in front of the kiln when I go in and load. If I don’t pay attention I could get stranded in the kiln and my shoes would be floating around in that front area. So, I load pots and glance back now and then to check the water level, plugging the pump in when it gets too high. I REALLY need one of those automatic sump pumps so I don’t have to keep switching it on and off manually. The water made it into the firebox Monday night, but not up onto the front floor of the kiln yet. We’ll see if it gets any higher by tomorrow (Wed) morning.

We are expecting rain through Thursday, so I’m a little worried about finishing the front setting on Wed evening, then waking up Thur morning to find all the pots sitting in and inch of water.

Even with the front area pumped out, the wind has been blowing the rain in, making it difficult to load the kiln. I nailed up a tarp to cover the entrance area. Later in the year, I’ll extend the roof properly to keep things dry.

One last item of interest: The company that manufactures Seger cones (Japan uses Seger cones rather than Orton) was in Fukushima, and was apparently seriously affected by the recent disaster. Consequently, Seger cone prices have tripled. They were 200 yen (about $2) each to begin with, but can you imagine paying $6 for a cone?! I had trouble shelling out $2, so I switched to Orton a couple years back. It is still WAY cheaper to pay shipping on Orton cones from America than pay for Seger cones here, even when they were practically a steal at $2 each.

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.