Whitewash is a lime-based product which was quicklime that had been saturated with water then mixed with binders to improve the durability and chalking resistance. The binders could be glue, salt, flour (rice, wheat, rye, buckwheat) skim milk, and borax. Because it is thick, it was applied with a coarse brush that left brush strokes on the surface.
Why is the White House white?
The building was first made white with lime-based whitewash in 1798, when its walls were finished, simply as a means of protecting the porous stone from freezing. Why the house was subsequently painted is not known. Perhaps presidents objected to the dirty look as the whitewash wore away.
"WHITEWASH, as used on the President's house, in Washington, is made as follows: Slack half a bushel of unslacked lime with boiling water; cover it during the process. Strain it, and add a peck of salt dissolved in warm water, three pounds ground rice, boiled to a thin paste, put in boiling hot, half a pound Spanish white, and one pound clear glue, dissolved in warm water. Mix and let the whole stand a few days. Keep in a kettle, and put on hot with a brush."
The above paragraph was from "the Ohio Valley Farmer" publication of June 1860.
Besides buildings, whitewash was also used to paint the bottom trunks of fruit trees to prevent sun scald and to prevent the tree from warming to rapidly in the early spring and causing blossoms to appear before all the frost was over with. Therefore preventing the blossoms from freezing and destroying the crop.
Below is a postcard that says "a scene near Delmar Del." Perhaps about the 1870s as one of the men is wearing a civil war style hat (one with the dog). The point of showing it is to show the whitewashed trunks of the trees.