[Daffynition]

>>I was just wondering if they actually could distinguish between a vessel that had contained wine and one that had contained wine vinegar.<<

I think they can...Bobby Ballard can. ;)

http://news.nationalgeographic.com/news/2003/01/0110_030113_blacksea.html

[TigersEye]

Thanks, Daffy! That is certainly close to an answer. Olive oil and fish would certainly leave a residue easily distinguished from wine. Oily substances would also have a much greater chance of surviving the centuries than those that are water soluble. There probably are chemical differences between wine and vinegar that would leave some trace fixed in the ceramic.