More Decanting

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By Robert L. Wolke
Wednesday, June 21, 2006

As a result of my June 7 column on the risk of lead leaching into wine kept in crystal decanters, I received several anxious e-mails from readers who want to know whether distilled spirits can also leach lead from the glass, as wines do. Here is a sampling.

Do whiskey and scotch also leach out lead, or are they not acidic? Is it the alcohol or the acidity of wine that causes the problem?

It's both. Most of the research on this subject has used a 4 percent solution of acetic acid (vinegar) as an excessively acidic but reproducible stand-in for wine. The more acidic the liquid, the more lead has been found to leach out. But the leaching of lead into water-alcohol mixtures depends quite strongly on the type of glass, so the effects of beverages with higher alcohol contents are not easily predictable.

My curiosity having been aroused by this question, I measured the acidities (pHs) of several of the liquors in my cabinet, all about 40 percent alcohol by volume. My collection of tequilas, mezcals and rums (Mexico and the Caribbean are my favorite fonts for firewater) all measured around pH 5.0, or about the same acidity as coffee. Jack Daniel's black label whiskey, Jim Beam bourbon and J&B scotch were more acidic at about pH 4.0, which is comparable to tomato juice. The two brandies I measured, Courvoisier cognac and Gran Duque d'Alba, were more acidic yet, at about pH 3.5.

How do these compare with wine? The pH of wines varies but is most commonly between 3.0 and 4.0. Thus, according to my small sampling, liquors can be expected to be less acidic than wine. But, of course, they contain more alcohol, so it's pretty much a wash.

Does the same danger of leaching lead exist with hard liquor? I keep single-malt Scotch and other liquors in Waterford decanters.

I always knew my readers were sophisticated eaters and drinkers, but single-malt Scotch in a Waterford crystal decanter? I'm impressed.

The degree to which you should worry depends not only on the acidities and alcohol contents of your beverages, but on quite a few other factors, including the age of the glass (brand-new and stored glassware have different leaching properties), how often it has been used and washed, and the amount of surface area and duration of contact between the liquid and the glass.

A comprehensive study of these factors, and the most thorough and best-controlled work on the topic I have seen, was published in Packing Technology and Science, 11, 45-57 (1998) by E. Guadagnino et al. of the Stazione Sperimentale del Vetro in Italy.

They found some good news and bad news. The bad news is that lead continued to leach out for as long as the experiment lasted -- 105 days, in the case of brandy -- although at an ever-diminishing rate. (For the mathematically unchallenged, the amount of lead extracted increases as the square root of the extraction time. That is, if 1 milligram of lead is extracted in the first day, there will be 2 milligrams after four days, 3 milligrams after nine days, 4 milligrams after 16 days and so on.) So the longer you leave the brandy in the decanter, the more lead it will contain.

The good news is that repeated extractions will remove ever-diminishing amounts of lead. That is, the more times a decanter or wine glass has been filled and emptied, the less lead will be extracted from the glass the next time.

I have four lead crystal decanters with vodka, rum and whiskey that I use for my evening drink (or two) every day. Do I have lead poisoning? I have no symptoms.

You seem to be more worried than most, and you apparently visit your decanters more regularly. So let me suggest an alternative.

I keep my fancy decanters in a glass cabinet in my dining room, just for show. But at my bar I keep my "provisions" in Pyrex laboratory flasks. Don't laugh. They're quite good-looking, they're practical and they're utterly harmless. Besides, they make you look scientific. There are two kinds: Erlenmeyer flasks have a conical shape, while Florence flasks have a round bottom. You can obtain Erlenmeyer flasks from Edmund Scientific Co. ( http://scientificsonline.com ) or Science Co. ( http://secure.sciencecompany.com ). A 1,000-milliliter Florence flask can be had from Science Co.

Find the right size cork stoppers from American Science & Surplus at http://sciplus.com .

Salud!

Robert L. Wolke (http://www.robertwolke.com) is professor emeritus of chemistry at the University of Pittsburgh. He can be reached atwolke@pitt.edu.


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