Whitewash is an inexpensive paint that is generally made with hydrated lime, and, when painted on brick, it creates a soft, old-world finish. The hydrated lime in whitewash recipes may go by different names, such as slaked lime or calcium hydroxide, but they are one and the same. The hydrated lime is a dry powder made from slaking, or chemically combing, quicklime with water. Whitewash was originally used on the trunks of trees to prevent sun scald and on houses for its reflective properties. It also is also mildly antibacterial. It is often used for decorative purposes, such as painting the brick on a fireplace or to give a shabby-chic look to a wall.
Use a wire brush to scour the brick wall and remove any loose pieces of brick. Dust the wall with a duster, and wipe it down with a wet rag until it is clean.
Fill a spray bottle with water. Lightly mist the brick wall to humidify it prior to applying the whitewash. It is necessary to humidify the bricks because it prevents them from absorbing the water in the whitewash. Wait until the wall is damp and not wet to apply the whitewash.
Put on safety glasses and rubber gloves. In a large rubber bucket, mix together the salt, alum, molasses and water. In another large rubber bucket, mix together the hydrated lime and hot water. Use an electric paint-mixing paddle to mix the solutions.
Combine the two solutions into one large rubber bucket after 12 hours have passed. Mix the solution with an electric paint-mixing paddle until it is a brushable consistency.
Use a paintbrush to apply a thin layer of the whitewash to the brick wall, applying the whitewash with even strokes and pressure. Mix the wash between strokes so it does not separate in the bucket. For an interior wall, apply three coats. For an exterior wall, apply five coats.
Remist the wall using the spray bottle between layers, using larger amounts of water with each successive coat.
Allow the wash to fully dry between applications, which may take one to three days.
Rub down the dry whitewashed wall with a clean rag.
To make the whitewash more durable, mix in Type I or Type II white Portland cement with the hydrated lime and hot water solution. Substitute 10 per cent of the lime with the cement. For this recipe, it would be 20.4 Kilogram of hydrated lime mixed with 2.27 Kilogram of Portland cement.
Wear protective eye glasses and rubber gloves when working with hydrated lime. It is caustic and can burn the skin. Work in a well-ventilated area when preparing the whitewash.