Flour paste answers the same purpose, but needs zinc sulphate as a preservative.
The following are from “1,000 More Paint Questions Answered”:
(4) Durable Whitewash for Outside Use.—A whitewash that will not rub off or wash off in rainy weather can be made by mixing one half-pint of flour to a batter with cold water, then stirring into this boiling water until it becomes a thick paste.
While still hot it is poured into a pailful of ready-made lime whitewash and well stirred in.
(5) Another simple method is to add to 2 gallons of ready-made lime whitewash one half-pint each of molasses and table salt. Must be stirred frequently while being used.
Whitewash for Exterior Surfaces.—A formula for a durable whitewash for out-buildings of rough lumber. The following is reprinted from “Popular Mechanics”:
(6) Place 1 bushel good fresh lime in a barrel with 20 lbs. beef tallow; slake with hot water and cover with sackcloth to keep in steam. When the lime is slaked, the tallow will have disappeared, having formed a chemical compound with the lime. Dry colours may be added to produce any tint desired.[10]
It is better to add colour before slaking the lime, but if this is not feasible mix the colour with alcohol and add it to the strained whitewash. Thin to easy flowing consistency with clear water.
Distempers and Limewashes
Cold Water Paint that will stand the Weather.—A formula for making a white outside coating that will resist the action of the weather and remain hard even under the influence of moisture and rain. Experiments with different brands of cold water paints have proved failures.