Maria the Jewess and the Bath That Bears Her Name

Every cook who sets a cheesecake in a pan of hot water to keep its top from cracking is using a piece of equipment named for a woman who probably lived in Roman Egypt. The French call it the bain-marie and the Italians the bagno maria. The medieval Latin behind both, balneum Mariae, means simply Mary's bath.

The Mary in question is Maria the Jewess, remembered as a founder of alchemy and often described as the first alchemist in the West who is not a mythical figure. She is also one of the hardest people in the field to pin down. Not a line of her own writing survives in its original form, and the story of her famous bath is less tidy than the name suggests.

Known through one witness

Almost everything about Maria comes from Zosimos of Panopolis, a Greco-Egyptian alchemist active around 300 AD. Lawrence Principe, a historian of alchemy who trained first as a chemist, calls Zosimos the first alchemist about whom we have reasonably reliable details, and even those survive only in scraps. Zosimos is thought to have written twenty-eight books on the art, nearly all of them lost. Greek alchemy as a whole hangs by a thin thread: Britannica notes that a single manuscript of some 80,000 words is the principal source for its history.

In those scraps Maria appears as an authority from an earlier time, cited with respect. Zosimos called her "the divine Maria," said she founded a school of alchemy in Alexandria, and devoted a short work, The Four Bodies Are the Aliment of the Tinctures, to her ideas. He also credited her with a book on furnaces and apparatus. If that report is accurate, the Jewish Women's Archive points out, she is the earliest known Jewish woman to have written a book.

Her dates float. The Jewish Women's Archive places her somewhere between the first and early third centuries AD, while other accounts settle on about 200 AD. One argument for an earlier date rests on the possible influence of her school on Theodotos the Gnostic in the second century, which is suggestive rather than decisive.

The bath and its purpose

Principe's summary of her contribution is plain. Among the techniques Zosimos credits to Maria is a method of gentle, even heating with a bath of hot water instead of an open flame. The principle is simple. A vessel standing in liquid cannot get hotter than the liquid around it, and water at sea level cannot pass 100 °C, so the contents warm evenly, without the hot spots that scorch or split.