Long ago, homes, sheds and fences were white washed to renew their white paint appearance. White wash may seem like a paint, but it isn't. It is actually a lime and water mixture that is allowed to activate into a paste overnight. There are many recipes available for white washing, some of which include additives that help to give a stronger bond to the wash's surface.
White wash applications are more like a thin layer of plaster than paint. White wash doesn't peel as paint does and has lasted on many houses as an exterior finish for over 30 years.
The base of a white wash paint is lime and water. For a very small batch of slaked lime, mix about 0.907kg. of lime powder with about 1 gallon of water. The water activates the lime, and the reaction generates its own heat, so there is no need to use boiling water. Mix thoroughly and let sit for about 24 hours.
The next step in preparing the white wash is to mix the same composition of salt and water, 0.907kg. of salt to 1 gallon of water. This can be made in advance and set aside until the lime is ready.
Once the lime is ready, pour off the excess water and mix in the salt mixture. The consistency will be very creamy. If you prefer a thinner white wash, add more water. Continue to mix well, then let it sit for another 24 hours before applying to the exterior surfaces.
While the basic lime, salt and water mixture is sufficient to make a good whitewash, there are many variations to this recipe and several different additives that can be used. The ratios of lime to water or salt to water may vary from place to place.
Some additives include overcooked rice or flour to add more adhesion to the white wash by reacting with the lime. Powdered white chalk may be added to give the white wash a more opaque white appearance. Diluted glue may be added for extra adhesion, and milk may be used to thin the white wash and react with the lime for a stronger bonding to the surface.
Prepare your work area by covering the floor or ground and washing the walls to remove any dirt or markings. Dampen the wall to help the white wash adhere to it. Apply the white wash with a paint brush, as its consistency does not work well with paint rollers. Use short but even strokes. Continue to cover the entire surface, then let dry overnight to see the true white wash finish. Touch up as necessary.