Friday, February 25, 2011
What does one do on a snowy day trapped at home? Being a potter who father always said, "you turn money into dirt....where upon I proceed to turn dirt into money....but make chowda bowls.
Maine is a great place for chowda and what a better thing to make on a day like this (so far we have about 12" of snow) than to anticipate hot piping chowda in one of my lovely chowda bowls. I made 42 of them today and tomorrow they will be ready for handles.
After messing around in the studio I came in the house and made chocolate chip cookies. The cookies are on a plate I made in the late 70s. That's 1970s....can't believe I have been making pottery for over 30 years!!!! And I am so young!!!! LOL
The plate the cookies are on is made from chocolate stoneware, how fitting. The glaze is Albany Slip, a natural glaze that used to be mined in Albany, NY. The mines have been closed and paved over and there hasn't been any real Albany Slip to purchase since the 80s. I found a bucket recently that I have and will soon be glazing some special addition pieces with this wonderful natural glaze this spring. I add a colorant to it to bring out the texture of the glaze. Will post a picture of the plate without the cookies once they are all eaten. With my sweet tooth of a husband it won't be long.
Enjoy the warmth of your home and I will show the finished chowda mugs in a couple weeks when they are ready for hot soups!!!!!
Wednesday, February 9, 2011
Cones are used in the firing process of making pottery. They measure the level of heat absorption to ensure proper firing and finished product. Kilns are not fired just to a certain temperature, but also to a specific cone level, or, heat absorption. Pyrometric cones are made from approximately 100 carefully controlled compositions and correspond (by number) to bend once a certain level of heat absorption is reached. The higher the cone’s number, the higher the level of heat absorption the cone is composed to measure. Starting at 10 (highest level), cones range down to 1 and then continue sequentially on: 01, 02, 03, etc. Each cone number is unique and measures within 30 degree temperature range.
Once my kiln is loaded and ready for firing, I place the cones throughout the kiln to ensure even heating. During firing I check the cones to see if they have started to bend. Cones look not unlike a gnome’s hat. Prior to heating they are bent to an 8 degree angle. As heat is absorbed, they begin to bend. Since the final temperature is most affected by the rate of temperature increase over the last 300 –400 degrees, it is imperative to keep a close watch on the cones. In a perfect firing, the cone will bend to a 90 degree angle.
Usually, I use “cone 5”. Below is an example of cones post firing.
Typically, I use sets of 3 cones. The triad of cones number in succession; if firing to cone 5, I would use a cone 4 and a cone 6 as well as the 5 to best measure the level of heat absorption. Once cone 4 begins to bend, I know I will need to begin shutting down the kiln.
Cones, cones, cones!