Wednesday, June 1, 2011

The Clay Has Arrived!

Well, it was two weeks later than expected, but the clay finally arrived. One ton - 2000 pounds - sitting in the driveway when I got to the pottery after work last Thursday. One ton of clay doesn't take up a lot of square footage. It looked pretty small sitting there, piled three boxes high in places, sitting on a palette and wrapped in that extra sticky plastic that keeps loads from shifting in the back of a delivery truck. But trust me when I say that there was a lot of clay.

To get it inside, I had to unstack it in the driveway first. The floor in the clay room tends to be damp, so putting the boxes directly on the floor would be a bad idea. That meant getting the palette out from under the stack. I haven't been in the gym for a month, so the exercise seemed like a good idea. I took great care to use mu legs rather then my back in lifting. Even though it's only fifty pounds at a time, it's a lot of fifty-pound lifts - specifically 40 of them - to get to one ton. The boxes were stacked a few feet over from the original pile, then I took the palette in and found a good spot for it in the clay room. Two ramps, one wheelbarrow and twenty trips later, all that clay was sitting indoors right by the pug mill.

Then I started reminiscing.

I had cleaned the pug mill out very carefully to avoid mixing any old clay in with the new. A little mixing is inevitable given that this particular machine has been in operation since the 1940s. It was built by the Crosley Machine Company of Trenton, NJ, which no longer exists. But they built this beast to last a very long time and with very little maintenance, it has done just that. Come the day that I move into my own digs, I won't be able to take this machine with me because its footprint is too big and I won't have the required three-phase power to run its motor. I will dearly miss it.

They built machines to last back when Rowantrees was first getting started. Still in residence at the pottery are the original filter press and pug mill from Crosley. The pug mill is still going strong, its huge 5 hp motor purring like a kitten and its gears meshing as well now as they ever did. You don't find many like them in the world these days.
The flywheel on the mill at Rowantrees is a lot larger than this illustration, and there is no clutch, but materially it is the same machine. The barrel holds about 150 pounds of clay and I would estimate its output at a good 600 pounds an hour (Crosely said 1 ton per day).

It has never broken down. Not once. Never. It requires grease from time to time, but that's it.

The filter press has had a somewhat more troubled past, but it has a lot more moving parts. And really, it's the pump that had most of the problems. Most of those problems stemmed from the fact that those of us using it on a regular basis were not machinists and consequently didn't quite know how to relate to it. So a small leak around the piston packing got fixed by putting in more packing. The occasional pebble that made it through the screening process might cause a valve to stick open. And the blankets could get creased easily, which would lead to a high-pressure spray of clay that could hit ceiling and windows before anyone knew what was going on. It led a merry chase now and then, but was generally faithful to its mission. I can still hear it's gentle whirr and thumping noises as the giant piston moved clay slip out of the tank and into the press. A few minutes of that would be followed by the sound of rain as water started raining and then dripping from the blankets. Three hours of that, and the clay cakes inside were usually ready for pugging and storage.
A tank beneath the press caught the excess water, which would be pumped back into the mixing tank and recycled for the next batch of clay. This illustration does not feature some options that the Rowantrees press has, like a relief valve that maintained a steady pressure of 80 psi.

Usually. It was a valve. Pebbles, you know.

The last time I used the press was probably sometime in 2008. I recall running a couple batches of clay through it without any fuss. But it has sat dormant ever since. By now the piping and valves are probably encased in dry clay. To operate the press now would require me to disassemble it, clean it and rebuild it. Time does not permit.

Rowantrees used local clay that usually came from local contractors. When I first arrived in Blue Hill, the clay supply had come from a local school construction project. It was unearthed when the foundation hole was dug. The problem with clay like that is that it is mixed with rocks, gravel and top soil, all of which has to be removed. Hence this process.

There are other ways of refining local clay that are less machine and labor intensive. They all require using clay that is dug from a much deeper depth and is consequently more pure. The potteries I know of that still use local clay use very pure deposits. Rowantrees never owned its own clay field, so the process is used was necessary.

But when you are a one-person operation, you have to choose how you will spend your time. I can mix and process clay or throw it on my wheel. Given the additional safety issues with mixing and processing clay, I decided long ago to switch to a commercial clay body. There are reasons beyond time in the shop, but I discussed those some time ago in earlier posts.

Despite this change in the traditional Rowantrees process, some continuity remains. The clay I have chosen is manufactured by the Standard Ceramic Supply Company of Pittsburgh, PA. Throughout its history, Rowantrees bought its raw glaze materials from Standard. Now the clay comes from them as well.

I have been throwing since last Friday. So far, I have produced 60 jam jar lids, 116 jam jars, 50 jumbo mugs and 60 cocoa mugs. I trimmed the jam jars today and will start on the large mugs tomorrow. This clay is fantastic to work with and will provide the same deep red color that the local clay did. I am looking forward to further exploration with this stuff.

But for now, I need bisque ware. Off and potting!