Martz Memories, by
Wedging Boards
A popular oriental method for removing the air from clay before using it for modeling, or throwing, is called kneading. The process is similar to the way we knead bread dough. However, that method was not good enough for Karl Martz and his students, so he showed another method that was more useful to us. We agreed the oriental way was successful with kneading, but working with clay day in and day out gave him experience that as students, we did not have.
One day I watched a professional flower-pot maker as he made pot after pot. It took him about a minute to throw each pot, and when he came to an air pocket in a pot, he would take a pinch of clay, press it into the hole, and continue throwing. With a few seconds more of throwing, he had a repair. Since then I have used that technique with success, but as students we were not expected to repair flower-pots or perform as skilled professional workers.
The device Karl had us use was called a “wedging board,” which started with a box about 15”x20”x8”. The box was filled with liquid plaster, and made watertight at bottom and sides with a long strip of scrap canvas. About twenty-one inches of the canvas were left hanging at the right side for later use. Holes and cracks were filled with moist clay. A backboard about twenty inches high helped support a sturdy post fixed to the back center. The post functioned to hold a wire for cutting moist clay, and the wire ran diagonally from the top of the post to the front center of the open topped box.
This container was filled with liquid plaster that was allowed to set. Then the twenty-one inches of canvas left hanging was brought over the top of the plaster and tucked in at the left. The wedging board was finished. In about two weeks the plaster would have dried enough to allow the block to be used. This “board” was meant to be heavy. It was designed to resist easy movement, and it resisted well.
To wedge, the potter selected a lump of moist clay, and began by kneading, in much the same way as one would knead bread on a bread-board. After a minute or two, the clay lump was cut in two by passing it through the cutting wire. The cut surfaces were examined to see if there were any air pockets exposed. The lumps were then thrown onto the canvas to drive air from the cut faces towards the backboard which now served as a spatter board. Advantages of this process gave the worker opportunities to examine the clay at the cuts, and to draw moisture from the clay to the plaster by prolonged wedging if that was the need.
Few class-room teachers could spare the space Karl’s heavy wedging board occupied in his studio. However, the advantages over the simple kneading process were obvious. Could a compromise be found? Would a smaller box containing less plaster serve a teacher’s purpose? For Karl’s board we started with a box. Obviously, that was a good place to start. My friendly green-grocer was happy to give me fruit boxes. They would hold four-inches of plaster. My artist friends often had strips of unwanted canvas, and two or three strips could be sewn together to cover the sides and bottoms of our boxes. In this way, making portable wedging boards employed re-cycling practices, and we were grateful for Karl’s problem-solving principles that helped us all.
Thank you, Karl.