Water Damage Plaster Repair is very common in WNY
These are all genuine plaster patches. Some small, some rather large. The dark grey/brown substance is the plaster basecoat, which is subsequently covered with lime and Plaster of Paris or Diamond finish. genuine plaster is continuously worked until it sets (becomes hard) and is polished using specialized finishing trowels. Which is why plaster often has the finish of glass. The process of finishing genuine plaster is significantly more labor-intensive compared to drywall finishing, as a plaster patch must be completed in one go, whereas with a drywall patch, you can apply multiple coats in staggered fashion.