We've all seen them. Those perfectly round rocks that look like discs. They are no more than a quarter of an inch or so thick and have consistently been found around pots.
I was told that these are pot lids, and that they have been found on pots. But then I also heard that someone said that their Indian grandmother used them to scrape and clean the inside of their pottery pots…
Just recently though, I heard probably the most convincing idea, because some people today are still using things that look just like them and are even buying them on the internet!
One website offers the following description:
Boil Over Preventer
"This is a product that controls or protects liquids from boiling over while cooking, often referred to as a "pot watcher" that is used to keep the liquid contained to a rolling boil rather than foaming boil. Various types of kitchen utensils and tips are suggested to prevent liquids from boiling over, such as placing a wooden spoon in the pan or to add a small amount of cooking oil to the contents being boiled such as pasta. However, as a means to use some type of tool that will assist with the preparation of foods when boiling water or liquid, there are solutions that have been developed as Boil over Prevention tools that can be placed in pots or pans, thus eliminating the need to place added ingredients into the water.
A cooking tool such as a small, round glass disk is manufactured which rattles in the pan as the water boils, thus making a sound to indicate the boiling point has been reached. Other solutions include small ceramic or clay-like disks designed to lie in the bottom of pots and pans that actually help to prevent the water from foaming out over the pan as it boils. The disks may be produced as a round disk or be formed into the shape of a food item for marketing purposes only, but regardless of shape, the material contained in the disk does effectively work to prevent water or liquids from boiling over."
So for this Thanksgiving holiday before your gravy boils over again this year, you might want to add an ancient tool to your list of kitchen utensils !