Mysteries of Sick Glass
Sick glass can best be explained by placing it in three categories. The first and most commonly encountered is a blue-white cloudy sickness that we will call oxidation sickness. The second is Crizzling or crackle sickness and the third and least encountered is soapy deposit sickness.
First let us discuss oxidation sickness. This sick glass is the result of surface degradation due to oxidation. The most common cause is water residue but other fluids and gasses speed the process such as salt, vinegar, wine or just plain air. The surface rusts just like iron and is the same chemical oxidation and reduction process. To identify oxidation sickness hold the sick glass under a spot light or desk lamp with the room lights off, if a blue haze is apparent with rings of white erosion towards or on the bottom oxidation has taken its toll. Sometimes it can be blotchy in appearance or evenly distributed perhaps getting lighter towards the top as will be the case for most decanters and bottles. Decanters that appear clear in normal daylight frequently show a light blue haze that is the beginning of the erosion process. In many cases the glass has also started to cloud up on the exterior due to oxidation by air but constant cleaning and less contact with dampness delays the process considerably.
The difference between good clear blanks and duller ones is frequently deterioration due to oxidation this applies to all cut glass shapes be it a tray or a decanter. Products and methods are available to mask oxidation sickness such as wax coatings, oil coatings or just damp interiors as in the case of decanters and bottles but the good news is permanent cleaning requiring resurfacing the sick glass surface is available. When this has been done the glass should remain clear for a long as it took to go cloudy from new, 70-100 years being typical.
Now lets discuss the second most common glass sickness, Crizzling or crackle sickness. This type of sickness can also be seen best under a bright spotlight in a darkened room. It appears as thousands of minute fractures over the entire surface sometimes arranged like miniature spider webs. The glass will seem to be dull in normal day light conditions and have a gray appearance. This sickness is the deterioration of the physical structure of the glass or devitrification as it is called. This condition is caused by the glass formulas or manufacturing techniques being faulty and no reversal of this condition is possible without melting the glass. It is however possible to improve the external and internal surfaces of this type of sick glass but considerable expense is involved and only the rarest pieces are worth saving.
The third most common type of sickness is soapy sickness. It looks like dried soap in the bottom of the miter cuts but it is actually a surface degradation or erosion similar to oxidation sickness. This sickness can be removed readily by mechanical buffing and is inexpensive for the results obtained.
Current methods available for restoring sick glass are mechanical- abrasive techniques and chemical milling. Chemical milling combines the acid formula used to polish cut glass when it was originally polished with current technology to stabilize the mixture to handle the wide variances in the glass formulas of the Brilliant Period.
In closing remember these things. Dont buy sick glass without allowing for the cost of restoration. Dont be fooled by damp interiors, oiled or waxed surfaces. Dont think that sediment can be just washed out, if it could be washed out it would have been. And finally dont buy Crizzling or crackle sick glass without expert consultation first. We hope this article is of help