The classicist Mary Beard (@wmarybeard) has a saucily titled piece, Banter about Dildoes, in the latest edition of The London Review of Books, in which she reviews Shopping in Ancient Rome: The Retail Trade in the Late Republic and the Principate by Claire Holleran (Amazon uk|.com).
In her review, Beard states:
The [Pompeii and Herculaneum food and drink] bars are a well-known conundrum. It always used to be thought that the big jars set into their counters held wine and cheap hot food, soups and stews – ladled out to a poor and hungry clientèle by an accommodating landlord or landlady. But the jars are not glazed, and could not be removed for cleaning. It doesn’t take long to see that they would be completely inappropriate for liquids, hot or cold – not to mention a deadly health risk.
I visited Pompeii in 2010. Never one to walk past a bar, I went into several, and even photographed some of the jars to which Beard refers (although I had no idea at the time that they were conundrums to anyone other than me):
Ever one to hypothesise, I have just emailed the following suggestion to the LRB. I'm sure I can't be the first person to suggest this solution to the conundrum:
Mary Beard (LRB, 3 January 2013) describes the conundrum of big storage jars set into Pompeii and Herculaneum shop counters, the non-glazed nature of which would make them unsuitable for food or drink storage.
In some hot countries, such as Spain and India, porous pots are still used to cool water. In a process similar to human sweating, water stored in the pots slowly seeps to the surface and evaporates, thereby cooling the pot and the water still inside. In a more modern, patented African take on this old idea, glazed food-storage pots are placed in wet sand inside larger porous pots to make solar-powered ‘pot-in-pot refrigerators’.
Perhaps Mary Beard's enigmatic jars were the Roman equivalents of wine chillers or salad crispers.
I had a great time in Pompeii, although I failed to track down the domus of the hero of my school Latin textbooks, Lucius Caecilius Iucundus.
You can see some of my other photos from Pompeii here.
Postscript (19-Jan-2013): A slightly edited version of my letter appeared in the 24-Jan-2013 edition of The London Review of Books.