Although not properly belonging to the plasterer's trade, this work is often included in the plasterer's specifications.
Common whitewash is made by simply slaking fresh lime in water. It is better to use boiling water for slaking. The addition of 2 pounds of sulphate of zinc and 1 of common salt for every half bushel of lime will cause the wash to harden and prevent its cracking. One pint of linseed oil, added to a gallon of whitewash immediately after slaking, will add to its durability, particularly for outside work. Yellow ochre, lampblack, Indian red or raw umber may be used for coloring matter if desired.
Whitewash not only prevents the decay of wood, but conduces greatly to the healthiness of all buildings, whether of wood or stone. It does not adhere well, however, to very smooth or non-porous surfaces. Two coats of whitewash are required on new work to make a good job.