Sigma-Aldrich Datasheets for Watch Glasses

Watch glasses are circular, slightly-concave pieces of glass that are used by chemists to evaporate liquids and cover beakers during sample preparation. They are also used to hold solids during weighing.
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Product Name Notes
Concave, clear annealed soda lime glass with fire-polished edges
Heavy-wall, borosilicate glass with fire-polished edge provides durability. May be slightly out-of-round due to O.D. variability.
Molded-in ribs allow vapors to escape during boiling to eliminate pressure buildup. Meets EPA requirements for methods 3005, 3010, 3020.
With fused edges. Manufactured from Duran borosilicate glass type 3.3 for maximum chemical and thermal shock resistance. Duran is a registered trademark of Schott AG.