Horsehair was mixed into plaster to keep it from cracking. The hair was cut from the tail and the mane and washed and chopped to two inches and stirred into the wet plaster. The hair distributed through the plaster like threads in cloth. When the plaster dried the hair held the plaster together across the shrinkage cracks. The cracks still formed but the cracks did not open because the hair bridged them. The hair was the reinforcement. The plaster was the matrix. Together they made a wall surface that lasted a hundred years without falling off the lath.

The plasterer bought horsehair by the bale. The bale came from the slaughterhouse or the tannery or the brush factory. The hair was a byproduct. The horse was dead and the hair was cut and the hair went to the plasterer and the plasterer put the dead horse into the wall of the living building. The building was alive with the remnant of the horse. Every wall in every tenement built before nineteen forty had horsehair in the plaster. Every wall had a piece of a horse in it. The horse that pulled the cart that delivered the brick that built the wall was in the wall.

The first coat was the scratch coat. Heavy on the hair. The scratch coat went on thick and the plasterer scored it with a comb to give the next coat something to grip. The brown coat went on thinner. Less hair. The finish coat went on thinnest. No hair. The finish coat was the face. The scratch coat was the muscle. The hair was the tendon. The three coats together made a plaster wall that was hard and smooth on the surface and tough and fibrous underneath. The surface lied about what was behind it. The smooth white wall had a rough hairy core.

Fiberglass mesh replaced horsehair. The mesh is stronger. The mesh does not rot. The mesh does not smell when the plaster is wet. Horsehair plaster smelled like a barn when it was fresh. The wet plaster released the smell of the horse and the room smelled like an animal for a week until the plaster dried. The plasterer did not notice. The homeowner noticed. The homeowner opened the windows and the smell went out and the plaster dried and the wall was white and smooth and the horse was inside the wall and the smell was gone and nobody remembered that the wall was part animal.

See also: Plaster Hawk, Lath