The replacement for the pearl ash (or pot ash) I discussed in my last post was something called salterus.

Salterus is bicarbonate of soda – yes, the stuff used for stomach acid or whitening teeth. We know it as baking soda and it is the leavening agent in soda bread.

This substance has been known for millenia. The Ancient Egyptians used it as a component of natron, the salt they employed to mummify bodies.

Umm, yummy. Using it for cooking seems more recent. (I read that the Native Americans used it but haven’t found additional documentation for this.) Anyway, baking soda works with something like buttermilk, which has a lot of lactic acid. In chemistry 101, we learn that the combination of an acid and a base yields carbon dioxide and that is what raises the bread.

Baking soda itself is pretty bitter. When I make soda bread I usually use baking powder as well. Pop quiz: what is baking powder? Well, it is baking soda combined with the powdered form of a weak acid but it also leaves less of a bitter aftertaste.