Plaster of Paris derives its name from the fact that it was originally obtained from rock quarried at Montmartre, a suburb of Paris. This common construction material indirectly led to the first law governing food adulteration in England in 1860. The addition of Plaster of Paris to flour and sugar was commonplace in those days in order to "extend" these expensive commodities with a cheap adulterant.
Unfortunately, one day a druggist's boy was instructed to add Plaster of Paris to a batch of peppermint lozenges but reached into the wrong bin and added white arsenic, a rat poison, instead. Thirty people died, but the tragedy precipitated the passage of the Food and Drug Adulteration Act of 1860. In a bizarre twist, calcium sulfate was one of the first food additives approved under the new Act. It is still used today by commercial bakers to provide yeast with calcium, an essential nutrient for these microbes. And that is why rye bread today is plastered!
