The transparent VYCOR® body and lid are made of No. 7913 glass (96% silica), which has high thermal and chemical resistance and is stable with acids, mild alkalis, water and steam. Vycor products can be used continuously at 900°C, and intermittently to 1200°C. These crucibles are useful in analytical work, particularly where ashing of the sample is required. Lids will be found useful for covering platinum or opaque crucibles. Note: Using covers of dissimilar material can cause spalling.