Glass Care – Part 1

We all use a lot of glass products in our every day life, and caring for the more common glass items is typically just a run through the dish washer. However, if you have antique glass vases, compotes, stem ware, etc., it may be helpful to know some of the following.

Glass is basically made of sand heated with lime and soda -with the manufacture method affecting the performance. If glass – particularly antique glass – has not been properly annealed (a controlled heat treatment to release stress), the glass may develop cracks for no apparent reason. Other outside elements that can contribute to this are smoke, sunlight or heat. In some cases, items can spontaneously crack causing the item to break into pieces. On a personal note, I had this happen to a lovely crystal compote. I was in the other room and heard it break -went into the dining room and there it way,  laying  in two pieces on the table. 

Glass can also crystallize causing it to lose its clarity and become delicate. You may have seen some glass that appears to have an iridescent look. This is caused by a chemical change when carbon dioxide in moisture reacts with a substance in the glass forming sodium carbonate and calcium silicate. This process usually takes many years – Roman glass has been found in this condition –  with the resulting patina typically being desirable. However, it is possible to remove the iridescence from some items  by very long soaking in several bowls of distilled water, followed by celluloid varnish.

Glass is absorbent and slightly soluble – in water. For example, if glass is stored in paper it can absorb dye or acid from the wrapping. Even if the paper is acid free, it would seem that too has an affect.Note: For this reason never store liquor for any length of time in lead-crystal decanters. The lead can leach into the liquid causing problems when you drink it.

The most common problem encountered with glass – in the home – would be the clouding or staining of glass. Unlike tarnish on silver, this clouding or discoloration is not simply a surface problem.

It is possible that the liquid may have very slightly dissolved some of the glass itself causing the glass to react with the liquid’s components. Some of the components in these liquids might be lime in water, salts in flower water, and tartrates in wine. There are many ideas about how to remove this ‘layer’ of film, but some removal processes can cause more damage than good. Some less aggressive ‘home remedies’ that have been tried are:

  • Ammonia
  • Vinegar
  • Denture tablets
  • Toothpaste

There are those that think the best ‘home remedy’ is to rub the stain with a fine abrasive. We’re not talking kitchen scouring powders. Using these will cause more scratches and damage. There are polishing agents on the market suited for glass and mirrors – and if you plan on trying to polish your own glass, be sure you get the correct product and follow package directions.

The only sure way is to have the thin layer of damaged glass removed is by acid – by a professional.   And, should you take the item to be restored, you will need to let the restorer  know what agents you used to try to clean the item. This will help to avert any possibility of damage to the item (or harm to the person) by the mixing of conflicting chemicals, so be sure to keep a record of the materials used trying to clean each item.

Next time we’ll cover glass breaks, chips, and stoppers.


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