Soaking new crystal in vinegar may sound like a superstitious old wives' tale, but it does have a purpose. Not all crystal glasses need a vinegar soak, however. If you have a type of crystal that contains no lead oxide, such as titanium crystal, it's not necessary -- though it can still benefit from vinegar for regular cleaning.
Lead Crystal Dangers
Lead crystal contains lead oxide, which can leach out of the glass and into your beverage. This is primarily an issue when the liquid is acidic, such as wine or juice. While the amount of lead that enters the beverage during an average-length meal is well below the safe threshold established by the U.S. Food and Drug Administration, acidic beverages should not be consumed from lead crystal glasses on a daily basis or by pregnant women or young children.
Vinegar is a highly acidic liquid that will attract lead from the crystal. Soaking new crystal glasses in a vinegar solution for 24 hours causes lead to leach out, leaving less surface lead to potentially leach into your beverages. Soaking in vinegar won't remove all of the lead in the crystal, so you should still avoid regular use of lead crystal glasses.
How to Soak Crystal
To soak your new lead crystal glasses, place a soft dish towel on the bottom of a plastic basin and pour 1 to 2 qts. of distilled white vinegar over it. Pure vinegar will leach out the most lead, but you can dilute it with up to 50 percent of the amount of vinegar to ensure that the glasses are completely submerged. Place the glasses gently in the solution; the dish towel will help prevent the glasses from moving and hitting each other. After at least 24 hours, wash the glasses with mild soap and rinse thoroughly with warm water.
Your new crystal glasses should be spotless, but if they appear dull from shelf wear, the vinegar will brighten them up. Washing crystal glasses by hand or in the dishwasher can leave water spots and a dull film from hard water, which can also be remedied by a soak in diluted vinegar -- about one part vinegar to four parts water does the trick. And, if you only use your crystal glasses a couple of times a year as recommended, the diluted vinegar solution removes any dust that's collected on them.