Table 2. Products mentioned in the text.

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Hydrostone: Gypsum cement, manufactured by United States Gypsum, Chicago, IL 60606
Mortar Color: Concentrated dye, manufactured by Solomon Girnd-Chem Service Inc., Springfield, IL 62705
Specimen Boxes: Clear plastic containers (about 19x14x10 cm) with friction fitting lids, manufactured by Tri State Moldeed Plastics, Inc., Dixon, KY 42409
3-in-One Household Oil: Light lubricant, manufactured by Boyle-Midway Inc., New York, NY 10017