I have an old crystal decanter, bought at Tiffany's circa 1950, that I would like to keep filled with port (18 percent alcohol) on my sideboard. I have heard that alcoholic liquids can leach the lead out. Would that be sufficient to be of real danger? And, even more important for my peace of mind, is it possible to determine whether it is, in fact, lead crystal?It was bought at Tiffany's, and you question its authenticity? O ye of little faith!

But first things first: Assuming it is genuine, don't keep your wine in that decanter. I'll explain.

True, there is enough fake "crystal" floating around to justify some suspicion. The word "crystal" cannot be trademarked, and every huckster peddling a chunk of glass can call it crystal with impunity. It's not very easy to be fooled, however, because genuine lead crystal is heavier and has a special brilliance. Moreover, the labor involved in cutting decorative patterns into glass bowls and decanters is not likely to be wasted on junk.

Lead crystal, known less ostentatiously as lead glass, contains between 18 and 38 percent lead oxide instead of the calcium oxide in ordinary glass. Lead oxide gives the glass a higher refractive index -- light-bending power -- so when decorative facets are cut into it, whether by hand or machine, it sparkles more brightly.

Old decorative crystal pieces were traditionally made of glass containing 32 percent lead oxide or higher. But today, manufacturers adhere to a maximum of 24 percent, the minimum amount that, according to a 1969 European Union directive, can be called crystal. The reduction was due to concern about lead leaching out of crystal decanters. Studies had found that wines and spirits stored for even only 24 hours in lead glass decanters contained alarming amounts of lead. As a result, the International Crystal Federation, an industry group, voluntarily set 1.5 milligrams per liter as the maximum amount of lead that could be leached over a 24-hour period from a small crystal decanter into vinegar (admittedly, a pretty sad facsimile of wine).

In practical terms, how much lead is this?

The U.S. Environmental Protection Agency has established an "action level" for lead in drinking water -- the level that will trigger regulatory action -- of 0.015 milligrams per liter. The 1.5 milligrams per liter of lead that may be lurking in your decanter is 100 times that amount.

Scary? Let's do the math.

Assume that your drinking water contains the action level of lead. If you drink two liters of water per day, you would ingest 0.03 milligrams of lead. In comparison, an after-dinner glass (3 ounces) of port from your decanter would contain 0.13 milligrams of lead. That's more than four times as much lead as you would get from all that water.

So to stay below the EPA's action guidelines, you have two options: Have a glass of port from your crystal decanter no more than once every four or five days, without drinking any water in between, or do not keep your wine in the decanter.

I strongly recommend the second option.

What about drinking wine from those beautiful crystal glasses you got as a wedding present and are afraid to use anyway, for fear of breakage? Tests have shown that the amount of lead transferred into wine by drinking it from a crystal glass over the course of a meal is well below the U.S. Food and Drug Administration's action level of 1 to 2 milligrams per liter in beverages.

But pour that wine from a bottle, not from a decanter kept on your sideboard. Or if you're determined to use that fancy decanter to impress your dinner guests, don't put the wine in it until only an hour or so before serving.

We brought some dishes back from Mexico and they occasionally have a white film on them. It appears when they dry after washing. Is it possible that this is an indication of lead in the ceramic? If so, can we test for it?Without analyzing it, I can't tell you what the white film is. But many clays used for pottery contain salts that can be extracted into hot water and then dry up on the surface. Ceramic ware can indeed contain lead, however, especially in the glazes, and that makes them hazardous for food use. Acidic foods are most effective in extracting lead from ceramics and earthenware.

Utensils manufactured in the United States can be expected to conform to the FDA's limits of lead content, especially in items intended for contact with food. But the materials used by independent craftspeople in this country may not have been inspected for lead content and should be viewed with suspicion.

Consumers should also be wary of pottery made in other countries. While commercially imported goods are inspected, travelers often bring home indigenous earthenware. The last time I was in Mexico I bought several bowls and cazuelas (terra cotta cooking dishes), all the while wondering whether I would risk using them after I got home. As it happens, I was spared having to make that decision because they all arrived broken.

But I could have tested them for lead, as can you. Many inexpensive lead test kits are available in hardware and paint stores and on the Internet. Just Google "lead test kit" and take your choice. But bear in mind that the sensitivities of these kits vary, and small amounts of lead may go undetected. Even for a utensil that tests negative, play it safe by not keeping food in contact with the utensil for any more time than necessary.

Robert L. Wolke (http://www.robertwolke.com) is professor emeritus of chemistry at the University of Pittsburgh. His latest book is "What Einstein Told His Cook 2, the Sequel: Further Adventures in Kitchen Science" (W.W. Norton, 2005). He can be reached at wolke@pitt.edu.