The WATER OF PLASTICITY is the percentage of water needed to make 100 parts of dry clay into a plastic workable clay. Some clays have a higher WOP than others (it is related to particle size and plasiticity). Students do not need to know any of this in order to answer the questions below.
Teacher can ask students a questions such as:
How could we start with this small piece of perfectly mixed soft clay in order to find out exactly how much water to use when we weigh out our dry scraps of clay to be soaked and made into perfectly workable clay?
If they cannot figure it individually, maybe they can do it as teams. Some lower grade children can think this through. Others have forgotten or never really learned how to think. Maybe they can solve it if allowed to think on it for a few days. Those that develop ideas can be asked to explain how they figured it out (some children resist using their brains because they have learned that waiting for the answer is easier less failure prone, some will find a willing adult to do their thinking, but others may report that the answer came to them by thinking). Once students have developed a theory (right or wrong), try it. When the problem is solved, the conclusion might be stated as a poster or placed on the white board. At this point I would congratulate them and explain the meaning of WOP.
USING THE RESULTS
One way to use the WOP number is described below. However, many teachers may want to relate art and science by having several teams of student scientists experiment to arrive a successful working process. The method below is not from the Big Book of Ceramics. It was developed experimentally.
1. Students put the correct amount of water in a plastic bucket or garbage can.
2. Pick out the big lumps of dry clay (scrap and abandoned or broken projects) and place them in the water (do not stir).
3. Let it set. Dry clay chunks will slake to mush.
4. Add the medium size and smaller lumps (do not stir).
5. Let it set. Dry clay chunks will slake to mush.
6. After all the big stuff is mush (overnight), mix it with the fine stuff (trimmings and remaining dust). Physically mix (kneading and wedging). Roll the too-soft clay into the fine crumbs and dust by reaching into the container to pick it up from inside the container. This thickens up the mix by wedging a bit. Caution students to fold the dust in carefully and gently to avoid breathing clay dust. Instead of handling dust, reach into the fine clay container with lumps of soft clay.
7. Let it set a few days.
8. Give it a final wedging and use it again.
If you had the right WOP it will be ready to use (note that evaporation can happen unless you keep the containers covered along the way)
Teaching PHILOSOPHY Question:
Is it more important to know how to do everything, or is it more important to learn how to think in ways to learn to do anything? Which takes more TIME to teach in the long run? Of course if you only need to learn a few things that are already known, it is always faster to learn it by rote or from example from others. However, when we are educated, we need to be able to learn an unlimited number of things in our lives. Many of these things are not yet known when we are students.