I don’t know of anywhere outside “the colonies,” but here in the United States, after the eggs are cleaned, they are treated with water glass, which is ”..a substance consisting usually of sodium silicate, but sometimes of potassium silicate, or both (” double” water glass), found in commerce as a glassy mass, a stony powder, or dissolved in water as a viscous syrupy liquid. It is used as a cement, as a protective coating and fireproofing agent, and in preserving eggs, etc.” – from Webster’s New Collegiate Dictionary, 1960 ed.
I have used it to seal porous cast iron engine blocks.