Why does Tree-ear suppose Min touched the clay with his eyes closed?

Tree-ear closely watches Min at work. As part of the process of making pottery, Min needs to drain the clay. This is because water needs to be mixed in with the clay and then poured through a sieve until all the pebbles and other impurities are removed. All of this takes a very long time, and this step must be repeated multiple times to achieve the right consistency of clay.
Tree-ear notices that when Min feels the clay, he closes his eyes. He supposes that this is because the right consistency of clay must be felt, rather than seen. Feeling the clay allows Min to appreciate the difference in the clay as it is poured through the sieve. As part of his apprenticeship in Min's workshop, Tree-ear tries to copy his master. But because Tree-ear is so inexperienced, it takes him quite a long time to get the process right.