Barbara Tipton, (Tipton 1983)
Clay forming processes
To determine the percent of shrinkage in a clay body, roll out a small slab slightly over 10 centimeters long. Press a plastic ruler (with raised numerals […]) into the clay from 0 to 10 centimeters. Even backwards, the numbers can be read easily. Then fire the slab as usual. With the ruler, measure the amount that the 10-centimeter length has shrunk. If it is 1 centimeter shorter, then the amount of shrinkage is 10%, and so forth.
Place a mirror in front of the wheel to reflect the wheel head. This is an invaluable aid when studying hand positions; it also makes it easier to compare them with photos when using a book as a guide. This process is also useful for viewing the pot as it is being made on the wheel, since it abolishes the necessiyt for the potter to step back to get a good view.
Centering with eyes closed is a useful teaching exercise for beginning potters. It helps them to regocnize that centering is first a tactile and then a visual process.