When a handful of earth or soil in a bank or elsewhere on a camp site sticks together when squeezed, and holds the finger imprints, it will have clay content-and the camp is fortunate! Experimentation will soon prove whether the clay is of high enough quality to use in making articles.
The refining of clay is a rather long and tedious (but very satisfying) process, and should be undertaken by older campers to create a supply for others to use. A supply that has been refined as a service by one group can be used at the beginning of camp, and replenishments made by expeditions and groups organized for that purpose throughout the summer. Natural clay may have interesting hues that will make the articles developed in the specific camp very distinctive.
1. Dig several pails full of the earth, and break it up into small pieces, allowing it to dry thoroughly.
2. Pulverize the earth by pounding with a mallet, through a canvas or burlap bag, or in a box.
3. Put through a 1/8" sieve.
4. Fill a pail half full of water, then drop the sieved earth on the water, stirring thoroughly with hands. Let soak for an hour, to make slip, stirring often.
5. Let sand settle to the bottom of pail, and pour off rest into another pail, pouring it through the sieve again. Let this mixture stand overnight.
6. Pour or siphon off water on top.
7. Repeat these last two steps until the mixture is the consistency of thick cream-or slip.
8. For modeling, repeat until clay is the consistency and feel of fresh putty.
9. Store in earthenware crocks or nonrusting metal containers.
10. Cover with damp cloths while storing, and when a piece of work has been started. A good storing place is made by using a big container, with a platform of wood or stones on which the crock rests. Water is put in the bottom of the container, and cloths spread over the crock, with the ends dipping in the water below. The cloths will stay wet, and keep the clay moist (Fig. IV-4).
Clay in powdered or moist form may be purchased from craft supply houses, and from many local outlets. Commercial clay has been refined and is ready for use. One form of clay that is good for camp use is a clay used in making flower pots; this is a relatively inexpensive clay, and one that lends itself to camp ware because of its earthy, red-brown color.
There are also forms of self-hardening clay that do not need to be fired. Craft supply houses list such clay in catalogs. This is clay to which dextrin has been added. The air hardens the clay after it has been modeled. It may then be decorated with poster paint and painted with a transparent liquid glaze, or shellac. This clay is more expensive than untreated clay.
Powdered commercial clay is prepared and used as is natural clay, starting at step 4 above, and repeating until clay is of desired consistency.
Store large amounts of processed clay in earthenware, zinc-lined or enamel containers with tight covers, or with dampened cloths to cover (see Fig. IV-4). Small amounts or pieces that are in the process of being worked may be stored in plastic bags, or covered with damp cloths.
When the clay has dried out and is too stiff to use, it may be made plastic by poking holes in it almost to the bottom of the mass, then filling the holes with water. Keep holes filled, and day should be workable in a day or two.
If clay is too moist to work, wedge it on a plaster slab, or place the work on a plaster bat. and leave until moisture has been absorbed (see Fig. IV-2 for plaster bat).
Clay is full of small air bubbles which must be removed before the piece is fired, or the heated air in the pockets will cause the piece to explode in the kiln. This working of the clay to remove the air is called wedging. It takes time, but is worth the effort. It should be done thoroughly. A hard working surface and a taut wire to cut the clay are necessary for wedging (see Fig. IV-5).
1. Make a lump or ball of clay, and cut it in two with the wire (Fig. IV-5).
2. Forcibly blend the outer surfaces of the ball together by throwing or pounding the mass on the flat surface. Knead the clay with fingers, and form new ball.
3. Repeat this process until the clay seems perfectly smooth, showing no air pockets or bubbles when cut in two (Fig. IV-6).
4. Use in this form, or store for future use.