Table 2: Products mentioned in the text.

Hydrostone: gypsum cement, manufactured by United States Gypsum, Chicago, IL 60606, USA.
Mortor Color: concentrated dye, manufactured by Solomon Grind-Chem Service Inc., Springfield, IL 62705, USA.
Specimen Boxes: clear, plastic, rectangular containers with friction fitting lids, manufactured by Tri State Molded Plastics, Inc., Dixon, KY 42409, USA.