Until the recent developments in breeding and artificial lighting, domesticated birds produced eggs seasonally: they would begin laying in the spring, continue through the summer, and then cease in the fall. So, just as they did for milk and for fruits and vegetables, our ancestors developed methods for preserving eggs so that they could be eaten year-round. Many of these methods simply isolated the eggs from the air and left them largely unchanged. Water saturated with lime, or calcium hydroxide, is alkaline enough to discourage bacteria, and coats the egg shell with a thin layer of calcium carbonate that partly seals the shell pores. Oiling with linseed oil apparently began on Dutch farms around 1800. The early 20th century brought the use of waterglass, or a solution of sodium silicate, which again seals the shell pores and is bactericidal. These treatments were rendered obsolete by the advent of refrigeration and year-round egg production.