Garret D. Bonnema on sat 20 may 00
Since throwing with coils is being discussed I want to share my experiences
throwing with coils on slab bases.
Certain pots that I make develope bottom cracks during drying. It may be my
throwing technique, our clay body, the drying conditions in our studio, the
shape of the piece, or all or some of the above. For example, I throw a lamp
shape out of stoneware clay that we call a Beehive Lamp. It has about a 10"
diameter bottom, is round and fat and is about 12" tall, sort of a beehive
shape. This March I had an order for one and I threw 4, using 12 lb. lumps.
Three out of the four developed bottom cracks drying. (We use wood heat and
live in Maine, so drying is a problem in the winter.) The next throwing
cycle I threw 8 beehives, using the slab and coil method, and none developed
cracks.
I rolled out a slab, 1/2" thick, and cut it into 10" diameter discs. I
placed a slab disc on a bat on the wheel and "worked" it in, as if throwing
a flat shape, thinning it somewhat in the process, and then retrimmed it to
the desired diameter. I rolled out a 10 pound coil and attached it to the
top of the outside edge and then threw that. I felt that the resulting
pieces where better thrown than if I had started with the 12 lb. lumps, and
they didn't crack. They did take longer to make, but the trade off was worth
it.
I have been using this method for quite a few years with the bigger pots
that I throw, 25-125 lbs raw, and have almost no problem with bottom
cracking. There is the extra benefit for me that I never have to handle any
more than 15 lbs. of clay at a time, and "centering" a 15 lb coil seems a
lot easier on the arms and wrists than a 15 lb. lump.
If anyone is experiencing bottom drying cracks or problems centering large
lumps of clay this might be a technique to try.
Garret Bonnema
Bethel, Maine
Dennis, Rhonda, Rachel Oldland on mon 22 may 00
Several years ago I used to have this problem.
I started turning the pots upside down when the upper part appeared almost
dry. I haven't had the problem since.Regards Rhonda
At 18:28 5/20/00 -0400, you wrote:
>Since throwing with coils is being discussed I want to share my experiences
>throwing with coils on slab bases.
>
>Certain pots that I make develope bottom cracks during drying. It may be my
>throwing technique, our clay body, the drying conditions in our studio, the
>shape of the piece, or all or some of the above. For example, I throw a lamp
>shape out of stoneware clay that we call a Beehive Lamp. It has about a 10"
>diameter bottom, is round and fat and is about 12" tall, sort of a beehive
>shape. This March I had an order for one and I threw 4, using 12 lb. lumps.
>Three out of the four developed bottom cracks drying. (We use wood heat and
>live in Maine, so drying is a problem in the winter.) The next throwing
>cycle I threw 8 beehives, using the slab and coil method, and none developed
>cracks.
>
>I rolled out a slab, 1/2" thick, and cut it into 10" diameter discs. I
>placed a slab disc on a bat on the wheel and "worked" it in, as if throwing
>a flat shape, thinning it somewhat in the process, and then retrimmed it to
>the desired diameter. I rolled out a 10 pound coil and attached it to the
>top of the outside edge and then threw that. I felt that the resulting
>pieces where better thrown than if I had started with the 12 lb. lumps, and
>they didn't crack. They did take longer to make, but the trade off was worth
>it.
>
>I have been using this method for quite a few years with the bigger pots
>that I throw, 25-125 lbs raw, and have almost no problem with bottom
>cracking. There is the extra benefit for me that I never have to handle any
>more than 15 lbs. of clay at a time, and "centering" a 15 lb coil seems a
>lot easier on the arms and wrists than a 15 lb. lump.
>
>If anyone is experiencing bottom drying cracks or problems centering large
>lumps of clay this might be a technique to try.
>
>Garret Bonnema
>Bethel, Maine
>
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