Category Archives: pottery

Handle Diapers and Stretchy Clay

The last couple of days I broke down and made some larger mugs and tankards. I generally avoid handled forms because most of the clay in my studio is not suitable. If you make a coil and bend it around your finger, it just cracks apart instead of bending. This time, I mixed a bit of plastic clay into the normal stuff to try to improve its plasticity. The mugs threw fine on the wheel, but again, when it was time to make the handles the clay was crap.

At first I tried pulling handles from a large ‘carrot’ of clay, but once you wet it, two pulls and it would be cracking apart and dropping off in your hands. Taking a different tack, I rolled out some tapered snakes, like Opossum tails but less stinky, and tried altering and attaching those, but when I tried bending them around to attached at the other end, they just cracked apart. The very few that didn’t crack ended up cracking a few hours later as they dried. Doh!

So this brings me to the current discussion of handle diapers. Sticking with the Opossum tail method I rolled out some coils. Then, before pressing them flat, I stretched a piece of plastic wrap over them. Making sure the plastic wrap was good and stuck to the clay, I attached the flattened handle to the shoulder of the cup, then turned the cup over and set it on the edge of the table.  Grasping the tapered end of the handle and the plastic, I lifted up the handle end and attached it. If any cracks appeared they could be eliminated by pulling on the two ends of the plastic which compressed the handle. Or, rubbing the clay through the plastic would erase them too. Leaving the plastic on, I placed them in styrofoam boxes to prevent rapid drying, hoping that it would also help the moisture to equalize between the cups and the handles. Today, I checked them after about 18 hours and they seem stable. None of the handles show signs of new cracks and they have firmed up nicely. The plastic is still attached but has puckered a bit from the shrinkage in the clay. It will be interesting to see if these dry completely without cracking.

Several years ago I ordered 100kg of white clay from Seto for making some Shino and Green Oribe ware. Never got past the experimentation stage for various reasons, but the clay is still taking up room in the studio so I decided to break it out and use it. I was double bagged in thick plastic and is still quite soft after almost 5 years. Unlike the Karatsu ‘clays’, this stuff is really clay, the stretchy kind, and it was great fun to play with. I made 600 gram lumps and threw some beer tankards. Then, pulled some handles and attached them, no fuss, no cracking, easy. I could get used to this stuff. It was so easy I decided to make some more this week for the firing at the end of Feb.

Plates for February

Here are some of the things that will go into the Feb. firing. Small plates that will be about 12cm fired, and some larger plates about 24cm fired.  Clay body is Karatsu white from Hara san and Kishidake clay 50/50, with pulverized sandstone and weathered Shirakawa porcelain stone wedged in.

Shirakawa Porcelain Mine

Took a hike up the mountain today to the now closed Shirakawa Toseki (porcelain stone) mine. This was the base ingredient for Arita’s glazes for hundreds of years. The mine is extensive, but I stayed near the entrance as old mines are not among the safest places on this earth. The passages from the main entrance radiated out in several directions and where light still filtered in, you could see that some of them extended several hundred meters. And that is just what you could see from the light filtering in. Who knows how much farther they go?

In the entrance area, pillars of rock were left to hold up the roof, but there were boulders in several places on the floor, from what looked like recent rock falls. The roof of the cave is probably about 20 feet tall. The expanse of white rock is really stunning to see.

Mystery Solved

The last firing of the wood kiln, I mixed up a glaze of 65 mystery wood ash and 35 Amakusa porcelain stone. I expected a dark green or yellow glassy ash glaze that didn’t run much. I even had the test tiles from around 5 years ago that showed what I’d get.

Well, I ended up getting a rust red sintered crust on every pot I put that glaze on, and it was a lot of pots. Even in areas that got up to cone 13, that glaze did not melt. It was very confusing since I had the test tiles showing a green glossy glaze.

With the new tiny kiln, I was able to fire twice today, 2 sets of test tiles. One set using the mystery wood ash from the crusty rust refractory debacle, and the other set using my normal mixed wood ash. Each set was fired for 90 minutes to cone 9 (yep, just 90 minutes to cone 9!) and all the recipes were exactly the same save for the type of ash.

I think it is safe to say that these ashes are not interchangeable. The mystery ash was from a neighbor’s wood stove, and I have no idea what it was. At any rate, it seems to have been reduced to almost pure silica. Sure enough, the glazes with the regular mixed wood ash turned out as expected. The atmosphere in the tiny test kiln is interesting. The 80/40 test tile came out reduced while the others were oxidized, only 2-3cm apart in either direction.

So, in short, mystery solved, and it didn’t require waiting for a big kiln firing. All in all, this tiny kiln is turning out to be very useful indeed, and easy to fire.

Test Kiln II

My weed burner came in the mail this afternoon and I wasted no time getting everything ready for the first real test of the tiny test kiln.

I prepared 3 sets of glaze tile pairs and set them in the kiln, along with one Orton cone (#6). I fired it up at 4pm. At 5pm cone 6 was flat. Easy peasy! Next time, all the way to cone 10, when I have some more free time for testing.

Okamoto Sakurei Show Pictures

Karatsu potter Okamoto Sakurei just ended a show in Fukuoka this weekend at Gallery Ichibankan. For those of you who haven’t heard of him, Okamoto san is a very talented artist making Karatsu style wares. He is well known throughout the country and one of the top Karatsu ceramic artists today. He will also be doing a demonstration/lecture for the  Workshop in Taku 2012: The Simple Teabowl.

During my visit we had a chance to discuss his upcoming presentation, as well as some wood firing diagnostics. Here are some of the pictures from the show. The gallery used a lot of natural light from its windows, which made for a very nice display, however it was not so camera friendly.