Since there were 3 rolls of insulating fiber left over from building the kiln, I decided to use them as added insulation over the first chamber. It took two of the rolls to cover the kiln, with one roll left over for future repairs. This new layer of fiber alone should help a lot with heat loss during firing, and it will be covered with more clay/straw mix, pretty much doubling the insulation over the first chamber.

I found a place in Karatsu that makes a clay/straw/sand mixture that they sell as the base layer for tile roofs. They can ship one ton of the stuff to my studio for about $90, or two tons for $120. REALLY worth it considering the work it takes to mix that much mud and straw. Also, it has much less shrinkage than the regular clay mix I used for the first layer. I made a 100mm test tile to test shrinkage, and the stuff only shrank 3mm from very wet to bone dry.

Here, the first stage is done, with some bricks holding the fiber in place, just in case some high winds come through. I’ll apply the mud in the next week or two, hopefully before the firing happens.

Today I spent a few hours making stop signs. Well, not really. I made bats. The recent discussion about bats on clayart got me to thinking about them, then I got an order for some large beer mugs and realized I needed some bats. Usually all the throwing done on the electric wheel is off the hump, so bats are unnecessary.

Anyway, the whole bat thread started with a little tiff over whether or not bat pins should be standard fare on all wheels. I am a non-pinner, because of the aforementioned hump throwing and although I am not against pins, I am against the exorbitant prices they get here in Japan for bats. More about that below.

During the clayart bat pin death match, David Hendley (a Texas potter) mentioned his bats, which fit around the wheelhead, not on pins. This type, incidentally, are the preferred bats in Japan, but they cost a bloody fortune at around $25 each. No really. They are a breeze to make, so I bought some plywood and went to work.

Plywood at the hardware store was about $16 per sheet and was pre treated on one side with some sort of water proof urethane finish. I got 3 sheets, which made me 24 bats in all.

Cutting the plywood sheets into 40cm squares.

Cutting off the corners, gives a nice stop sign. I could have done circles, but I didn’t have the right bit for my router. If you don’t have means to cut a circle this shape works well. If you are worried about the corners you can keep cutting them until you have close to a circle. My saw horses were lent out, but this ladder on it’s side worked great.

Tap center the bats on your wheel head, and sneak a sharpie under them to draw a circle around the circ. of the wheel head.

Here I used some screws to set blocks in place, to test tightness of fit. They were a bit loose, so later when I attached them for good a jiggled them in over the line just a tad.

Here it is sitting on the wheel.

And underneath view… You can see the cleat contacting the wheel head.

Final gluing. Titebond III is my favorite wood glue. Very strong, water resistant when dry, and no fuss. Cleans up with a wet sponge. I did the first couple with screws to clamp down the wood cleats, but it really wasn’t necessary with the weight method (below) which is much easier.

All the bats finished with 2 pugs of clay ‘clamping’ them down. Make sure all the cleats stack over one another, just like how you stack shelves in the kiln. The first few I put the cleats on with the bats in different directions. Makes no difference in the end, but for this clamping method, it prevents having a cool looking uniform stack. Dang. After the first 7, I finally got wise and assembled the bats oriented the same direction.

Here you can see the cleats lined up in the stack. After a night to dry, they should be good to go!

So, all in all, 24 new bats for about $50 and 3 hours of work. 24 new bats of this type would have cost about $600. All in all a worthwhile project.

It was my eldest son’s birthday, and he requested we go fishing. It has become a sort of birthday ritual for us by now and we have a great time, especially when we catch fish. Today we did pretty well. Our neighbor’s daughter came with us, she is a fishing machine! Total concentration.
Two Bream and 7 small Yellowtail were the catch of the day. I lost 2 large Yellowtail, one to a weak leader line, and the next to a hook that wasn’t set properly. Fought it for a good 3 or 4 minutes before it shook the hook off. I’m still frustrated about that one. It came up high enough once that we could see it and it was probably about a 12 pounder. Aargh!

Here are some of the flowers starting to bloom in the garden/area.

 Cherries in the park at about 60% open.

Weeping fruitless peach in our yard, with nice bright colored buds.

There was a recent thread on clayart about sand vs grog, and sand has been on my mind since I  started making some teabowls for the upcoming firing. While I cannot speak to the truth of any of the statements made in the email thread, such as excessive cristabolite formation, sand creating micro pockets of space as the grains shrink, etc… I can speak a bit about the function of sand in Karatsu pottery.

I really goes back to the technology that the Koreans brought over with them. They commonly worked with porcelain stone which is not a clay but rather closer to a high alumina content feldspar. They knew how to work with stone as a clay body. Here in Saga there are a great many clays that have reasonable plasticity but they are so refractory that it is difficult to vitrify them, or they have such large particles that even if they do vitrify, they still leak.

How they solved these problems to create vitrified bodies is still a bit of a mystery, since the technology was all but lost, but recent research has indicated there may be significant additions of crushed sandstone in the clay bodies, OR the clay bodies may be entirely of crushed sandstone in some cases. I know of one contemporary potter here who does this successfully.

Of course sandstones vary and I’m sure some are not suited to add in large amounts, however there are many places here where feldspathic sandstone can be collected. It is very fine since it was run through a stamp mill. Here is some I collected in Sasebo, Nagasaki. There is about 1.5 kg there in the picture and it will get mixed in to about 4kg of clay.

You can add more, but it starts to affect workability pretty quickly. My teacher often adds up to 50%.  There are several benefits:
1. the clay body is more easily vitrified.
2. the body is strengthened and actually less prone to slumping at high temps. (this is kind of counter intuitive from no.1 above, but testing shows it to be true).
3. you get a much more interesting trimmed foot with much crinkling and tearing. With feldspar glazes, you get a nice crawling of the glaze on the trimmed surfaces, called “kairagi” or plum tree  bark, such as can be seen on the famous bowl Kizaemon.

The workability of the clay is affected, depending on the mesh size of the sand, and you may find that you need a different firmness in the clay to throw successfully. This hump was too firm because I let it sit too long on the plaster, and I had some problems with it.

I hate it when this happens.

I really hate it when this happens.

 Finally got one right here. It has a few of the important points for an Ido style bowl. The inside of the bowl is not round at the bottom but rather pointed, which is a better shape for preparing thick tea (koicha), and the inside surface is smooth, so that the tea will flow to the lips without sticking and hanging in bumps and ridges. Also, the inside lip surface doesn’t curve in or out, just extends into space, and the outside of the lip curves upward and in to meet the inside. This creates a ‘sharp’ edge which cuts the flow of liquid nicely against the upper lip. I never really got the importance of this last one, until I had a chance to drink koicha from an Ido style bowl. The whole process of drinking and wiping for the next drinker made the efficacy of this lip treatment very apparent. It was one of those “Oh, I get it now…” moments.

Bottom picture is taken in my nifty new pot mirror, 540 yen at Nitori. I love this mirror because I can see the profile of the pot without leaning over. When I lean over, I usually whack my head on the ware racks to my right. And no, I don’t seem to remember from time to time, so it is always an annoying surprise.

Lastly, the ‘rack that whacks’ with pots all lined up and happy. That rod sticking out horizontally at the center left is the one that is particularly dangerous. If you don’t hit that, then you hit a ware board edge, or worse yet, a nice fresh pot gets squished by your temple and you have to clean clay out of your hair.