Last Updated: Jul 19, 2018 Views: 976
Hello! Thank you for your question. The film you describe is caused by the atmospheric deterioration of glass known as "crizzling" or "glass disease," in which the glass is sometimes referred to as "weeping." See the full definition of "crizzling" in the Glass Dictionary.
Pages 117-120 of Stephen P. Koob's book, Conservation and Care of Glass Objects (London : Archetype Publications in association with the Corning Museum of Glass, 2006) explain why some glass crizzles and describe the initial stages of crizzling. You can also check out the following brief article, "Crizzling," in All About Glass on the Museum's website. The CMoG blog post, "The Osler Candelabrum and Incipient Crizzling," also discusses the early stage of crizzling and how our conservation lab addresses the issue with Museum objects.
In a conversation with Koob, he added that we don’t use the word “oily” to describe the feel, but “slippery" or "slimy." He explains, "It’s the alkali leaching out, so it’s slippery like soap (another alkali)."
Please do not hesitate to contact us with glass-related questions in the future!
- Is glassware that has leached this slippery film safe to use (after washing it, of course), or is it advisable to throw it away? Should I be worried about food storage in certain glass jars? I can't seem to find any information on this that talks about whether glassware that leaches alkali is hazardous.