In the last week, the masons have started to apply the scratch coat. After they chipped off about 1 1/2″ of the damaged brownstone, they built the surface back up by applying layers of the scratch coat. Before they applied the scratch coat, they first applied a slurry coat as bonding agent. The scratch coat is composed of portland cement, lime, sand and water that was mixed on site. In order for the scratch coat to harden properly, it needs to cure for at least 21 days with temperatures above 40°. The masons started applying the scratch coat from the top down. Each scratch layer is scored for better adhesion.