Part of my third day was spent running a very large cornice. The horse, or template that contains the knife, was at least 36″ x 40″ in dimension and it took two people to run it. A fellow plasterer, Rubin, and I were asked to run this thing and it was interesting to say the least.
This running will eventually be coated in silicone rubber and be used as a mould, but before that can happen, the positive must be created. A core of styrofoam was built up to fill the mass of the sides and plaster was then poured on top. It took over five bags of plaster to create an eight foot section of this cornice! That’s a lot.
As hard as Rubin and I tried, we still ended up with a couple of waves and texturing. In other words, it was no good. To resolve this, plastic sheeting, similar to plastic wrap, was placed on top of the existing plaster. This creates a barrier between the old and new plaster so that moisture isn’t drawn from one plaster into the other. WHile Rubin was tending to other shop needs, Nathan and I ran the horse over the existing piece by adding a 0.5″ piece of plywood to the bottom of the horse. This elevated the horse just enough to go over the piece again.
Although we fixed the waves, texturing, similar to a basketball still occurred. This was due to inconsistent pressure along either side of the horse. A fan was placed on the piece to accelerate the drying time, and Nathan was scheduled to resolve the texturing effect the next day.