After the pigment trials and recipe tweaking was over, it was time to get to work on colorwashing the house.
Before the use of commercial paint was widespread, people made their own. Most communities had a lime kiln, or their lime was shipped in--often the lime was made from baked and ground oyster shells. The mixes were various combinations of water, lime and pigment, with a protein fixative added to keep the pigment and lime tight to the wall. On the farm (and in town) milk proteins were used to bind pigment to the walls for light colors and interiors. For exteriors, especially for farm buildings, paint is not for aesthetics, but to protect wood and keep it from rotting. Where huge exterior spaces had to be covered, typically a more abundant source of protein came out of butchering, when blood was reserved to fix pigment during autumnal painting. It's no accident that traditionally barns are red.
Obviously, we weren't interested in using either milk or animal blood to colorwash the house. However, alternatives to the traditional fixative materials are hard to come by. Fortunately, we found a supplier of casein protein, which we can use in place of milk or blood. The other option, which we tried first, is linseed oil. It works but, being oil, it's a real pain to use. It's hard enough to keep the lime and pigment in suspension by near constant stirring, without having to worry about the oil separating out. Casein is at least water soluble, which also makes cleanup a lot easier.
We've developed a protocol for colorwashing. The first coat is plain limewash, or whitewash, the stuff Tom Sawyer got out of painting on the fence. Limewash, applied to properly damp mortar, forms a chemical bond that seals the lime to the face of the brick, particularly good for fixing the faces of badly weathered bricks. The first coat dries white.
Weathering on brick faces, partially smoothed by first coat of limewash.
The second coat smooths the weathering and fills the little cracks and fissures more. This coat contains a little pigment, enough that, when it dries, it dries pink.
Even deeply flawed bricks, like the one in the header course, get some renewal from the lime treatment.
Several coats of limewash (approximately eighteen pounds of lime spread over a twenty-five foot wide, two and a half story surface) on a wall effectively ensures that water at least won't pour into cracks and further degrade the wall. Nothing will stop the old bricks from absorption, but the trick is really to manage the absorption and allow the water to evaporate to the exterior. Otherwise it would work its way through three courses of brick and damage the plaster on the interior, causing efflourescence and flaking.
Finally, the last coat is mostly red ochre, or hydrated iron oxide. The color is mined in the Blue Ridge and was, we strongly suspect, the original color of the house. We found Earth Pigments in Arizona, who provide pure pigments for restoration, and got both casein and ochre from them.
The final coat is heavy on the ochre, light on the lime, and this is the coat that restores the color. The photos below are of the south wall, finished, on the left, and the north wall, half-done, on the right. The bottom section of wall has first and second coats in place, the left side unpainted and the right with its first coat in place.