I've been reading a memoir by a woman who worked as a cook's helper in the early 1900s. She explains that the cook would put egg shells in the stock and then whisk vigorously. (She doesn't say how finely broken up the shells were.) This would be done for a clear stock to be served as a consomme. It was then this helper's job to carefully skim all the fat from the surface. Does anyone know the purpose served by the eggshells? Apparently they help fat rise to the surface of a liquid? She definitely was not using the eggshells themselves to scoop fat off the surface - they were being whisked into the liquid. Thanks!