The tops are marked in blue enamel and the bottoms are marked in white enamel to make sorting easier. Bottoms also have a triangular, enamel reference point for serial dilutions.
These flat, clear dishes will withstand repeated sterilization (wet or dry). The edges are beaded to provide greater mechanical strength. The bead also provides a means to equally space the sidewalls of the bottom and cover, thereby reducing the capillary action of condensed moisture on the slides. They are not effected chemically or thermally by any of the methods commonly employed in laboratories where sterilization is a major factor in routine or in specialized work. The covered dish is not airtight.