On their way to class I have my students pick up a "super size"
drink at the local fast food restaurant. We use the lids for "shims"
to lift the stones when the bezel is too high or the stone is very
thin. They just lay the stone on the lid, trace around it and cut it
out with scissors.
We then use the empty cup as a mixing bowl for mixing investment
during the casting projects. After they have poured the investment
into the flask they throw the excess investment and "mixing bowl" in
the trash. That way there is no opportunity for them to be motivated
to wash out one of the rubber mixing bowls in the sink and plugging