Sick Glass Can Be Healed

by Alex Citron
Issue No. 379 - November 2004

Some time back, when I was helping clean the glass the NCC had acquired from the Bellaire Museum, I heard the term "sick glass." That was new bit of jargon to me, so I asked around a bit. Apparently, this malady coats crystal or transparent colored glass with an unwanted fog. To most, its cause was a mystery, and its cure a cause of some frustration.

Unlike the patina that develops on old furniture or farm implements, this fog is entirely unwelcome to glass collectors. Besides cracks,chips and obvious repairs, it seems to be the number one turn-off in glass. It's damage, plain and simple, and it will drive down both the appearance and value of a piece dramatically.

I've learned that it does not only affect old glass. New glass can develop this fog as well; etched by dishwashers or marked with hard water stains. My recent research on the Internet has presented several remedies for sick glass. I have tried a few with good results.

The Calcium... To understand how to clean sick glass, one needs to know what causes it. It's no accident that the malady most often afflicts glass that is filled with water, such as vases, bowls, or drinking glasses. That's because most water, especially the variety that runs from your tap, contains dissolved mineral deposits, including calcium. The calcium, which exists in high concentrations in water that is considered "hard," is near invisible until the water evaporates, leaving calcium deposits behind.

The Cures... In cases where the calcium build-up is light, experts recommend an old-fashioned mix of 3 parts water and 1 part vinegar. If you leave slightly cloudy glass to soak in this mixture for a few days, it can help quite a bit.

I have read that some dealers rub Vaseline on glass to cover hard water stains. This will hide the fog well, until the Vaseline has dried or rubbed off. It's a temporary fix, and a pretty shady one if you're selling the glass in question.

I have read stories from people who, desperate to clean their clouded glass, have soaked it in straight ammonia or hydrochloric acid. These strong chemicals will eat through the calcium, but they don't stop there. They can also eat into your glass, leaving rough spots - even small craters. There's not much to do to repair that kind of damage. Collectors would be wise to avoid acids and harsh chemicals, unless they have experience with them.

Toothpaste or a denture whitener will take calcium off glass. These tooth cleaners also clean the tar deposits from cigarette smoke off old glass. Put a dab on your index finger, rather than a toothbrush, and then give the glass a gentle, circular rub. Rinse it off well. Bathroom cleaners also seem to be effective calcium cleaners. Tub and tile cleaners have worked on some glass; one dealer I e-mailed also recommends cleaners designed to take calcium deposits off of glass shower doors. She told me that CLR was her favorite glass cleaner, but that Dow "Scrubbing Bubbles" works well too.

Whatever cleansing agent you use, experts say you shouldn't let the chemicals sit on the glass for too long. Wash it off immediately with some mild soap and rinse it with luke-warm water. If the water is too cold or too hot, the glass could crack or shatter, so be careful.

Perhaps the best way to keep your glass free of calcium deposits is to never let them build up in the first place. Obviously, don't let water stand too long in glass. Keeping water out of glass prevents it from evaporating and leaving calcium behind. After you empty a vase or bowl, wash it out with mild soap and water. Don't let it air dry; use a soft, lint-free dish towel.