Glass should be stored in dry, ventilated conditions as damp can cause white cloudy stains. A glass wrapped in damp newspaper can be permanently marked with the newsprint and a damp glass can be permanently stained in a few hours by strong sunlight. Decanters should not be stored with their stoppers in place in case there is remaining damp inside
In common with ceramics, glassware should never be put in a dishwasher as the salts and detergents may harm the surface and cause cloudiness. Wash glass carefully by hand in a plastic bowl with a towel or foam mat on the bottom. Use warm water and a little washing-up liquid and wash only one piece at a time. If the glass is very dirty or greasy, a few drops of household ammonia can be added to the water but not if the piece is gilded. Dry carefully and thoroughly while the glass is still warm using a lint-free cloth. A warm hair dryer can be used,well away from the sink and water, to dry the inside of decanters or other vessels or place them upside down in an airing cupboard for 24 hours. You can also roll up paper kitchen towel, push it into a decanter until it touches the bottom, being careful not to loose the end, and remove it 24 hours later.
Hard water left in glass can leave deposits of calcium carbonate, and alcohol will often leave dark stains which can be treated with a solution of denture cleaner and warm water or with an organic acid such as citric acid, white vinegar or a mixture of one tablespoon of salt to a quarter of a pint of vinegar. Whichever is used, leave in the glass or decanter for 24 hours, shaking occasionally, then rinse and dry thoroughly. If stains are still there, repeat the process although it may not be possible to remove them completely. Do not use stronger acids as they may etch into old glass.Alcohol-based perfume bottle stains can be treated with methylated spirits or pure alcohol. This should be changed every hour or so until the stains have gone. If attempts to clean glass using these methods fail, the process can be done professionally for a relatively low cost. Specialist glass dealers can usually advise on reputable cleaners. Glass which has become 'crizzled' with a network of fine surface cracks and all ancient excavated glass should not be washed, and should be handled as little as possible.
It is best to leave restoration of broken ceramics and glass to a professional restorer. An amateur effort may not be easily reversible, especially if the wrong type of glue has been used, and can result in a more difficult and expensive professional repair later. When a breakage occurs, carefully collect each broken piece, no matter how small or fragmentary, wrap them in acid-free tissue paper and place in a box to prevent further damage or loss. Modern adhesives and the skilled repainting or glazing of ceramics can make repairs almost undetectable, although the restored area may discolour in time and of course the value of the piece will be affected. Repairs to glass are rarely invisible unless the break is in a place such as between the bowl and stem of a glass. However,much can be done with modern synthetic resins and some chips can be ground out causing very little loss of value.