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Glassware – Crystal Clear or Dull and Cloudy?

Just as normal glassware, polycarbonate glassware can get dull and cloudy to look at. If treated with care, polycarbonate glassware from Glass4ever however can maintain a lifespan of up to 20 times that of ordinary glassware.

According to The Clemson University Cooperative Extension Service Glassware washed in a dishwasher can be clean, but may remain cloudy.  It is important to identify the cause of cloudiness in order to determine how to deal with it.

The two main types of cloudiness are:

  • A build-up or a film of matter on the glass
  • Etching or leaching out of metals ions    from the glass

To determine the type of cloudiness, try scratching the surface of the glassware with a pin or other sharp object.  If the pin scratches off some of the cloudiness, it is due to filming build-up.  Another way to identify the cause is to drop some vinegar on the surface in a cloudy area and rub with your finger.  If the surface is clear when it has dried, the type of cloudiness is a film.  If the surface of the glass seems pitted after scratching it with a pin or if the surface remains cloudy after rubbing it with vinegar, the cause of the cloudiness is probably etching.


The most common cause of filming is water hardness. The calcium and magnesium in hard water drops left on glassware at the end of the washing cycle will dry in place.  Detergent will not remove these spots. The next time they are washed, new spots will leave more hardness minerals which will increase the amount of filming.

Food films can form on glassware and dishes when the calcium and magnesium in hard water combine with protein in the residue of milk, soft cooked eggs or rare meat.  Hot water also will act to denature or “set” these proteins.

A hardness film build-up can be removed by treating with an acidic material such as white vinegar or citric acid.  Commercial products also are available. Exercise care when using these products to prevent damage to metals.  Follow dishwasher manufacturer’s instructions to get the best results.

If water is hard, 6 grains per gallon or more, and if glassware begins to get cloudy or becomes spotted, try using more detergent.  Adjust the water temperature to 140o F and use a rinse additive.  Rinse additives are chemical wetting agents that permit water to “sheet off” glassware instead of clinging and leaving spots.

Food films can be removed by hand washing and drying.  The reversal of protein denaturation cannot be reversed through the chemical, mechanical or thermal action of detergent solution in dishwater.

Food films often are related to water hardness, but if a pattern is recognized in this problem, such as residue from eggs or meat, it may be wise to pre-rinse items with these soils.  Also, such food films may be worse on plastics where the finish has been scratched or worn thin.  Replacing older dishes may help.


Naturally soft water is corrosive and mechanically softened water is even more so.  The combination of soft water, alkaline dishwasher detergents, the chemical composition of glassware, and excessive water temperature can cause erosion or pitting of the surface of glassware.  This condition is referred to as “etching” or permanent filming, for the film cannot be removed.

The first sign of etching is iridescence, a “rainbow” appearance on glassware or on the glaze of china. Poor quality glassware is not necessarily more likely to etch than fine crystal.  It is impossible to predict which glassware is most likely to have this problem. The true cause seems to be related to very soft water and/or the over use of detergent since the largest component of a dishwasher detergent is polyphosphate, a water softener.  Metal ions are readily dissolved out of glassware in very soft water. Extremely hot water can speed this process.  When etching is identified as a probable cause, try using only one tablespoon of dish washing detergent in each detergent cup.  Hand wash and dry antiques and other fine glassware that may be difficult to replace.

Here is the full article from The Clemson University Cooperative Extension Service about the cause of cloudy and dull looking glassware and a few ways to stay on top!

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