Eggs decompose from the admission of germs through their porous shells. To prevent this occurrence it is necessary to protect the eggs from contact with air. When first laid, eggs have a protective mucilaginous coating, which is, however, removed by washing. They may be coated with varnish, paraffin, tin foil, butter, glycerin, vaseline, or any fat or oil not liable to become rancid. A 2- or 3-per-cent solution of salicylic acid may be added to the oil. Packing in sawdust or bran also excludes the air to a slight extent. Lime with cream of tartar preserves eggs, but alters their taste.

According to C. F. Langworthy (U. S. Department of Agriculture Bulletin No. 128, 1901) the best preservative substance is a 10-per-cent solution of water-glass, in which eggs will keep fresh for three and one half months. Eggs also preserve their freshness for as much as a year in cold storage at 300 to 400 F. Eggs so stored must be turned twice a week to prevent gravitation of the yolk, causing its adhesion to the shell.

Eggs are also preserved by drying, canning, and similar processes, when designed for shipment upon long voyages.

Evaporated or desiccated eggs are dried in vacuo or otherwise by currents of warm air. Salt or sugar may be added, and the eggs are ground. Such eggs keep well, and are often used by bakers.