How 2 Make a Cornice Mould (Crown Moulding in Plaster of Paris)

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A section of Cornice Mould
A running mould is constructed , with the template being an exact 1-1 copy of the finished profile Using the same techniques as running a panel mould A section of moulding is then run on the bench. This is know as the core
Once the core has dried out it needs to be sealed with three coats of shellac, then two coats of vegetable oil to act as a release agent
Using screws the core is secured to the bench. Also stop end need fixing into place
A canvas hessian will be used for reinforcement, this needs measuring and cutting prior to mixing the casting plaster
Using a splash brush , the firstings are splashed onto the core. By splashing you get a better cover, and less air pockets on the face of the cast
When the core is totally covered , the strike offs need cleaning to remove any splashed material
When the firstings have started to set the canvass hessians can be laid into place. The edges of the canvass hessian are folded back into the cast so the do not protruded the finished cast.
The seconds are mixed and poured over the canvass hessian , and filled level with the strike off points
Using a joint rule the seconds are ruled off level with the strike off points
All the strikes offs are cleaned and the cast is left to set
Once the cast has set , and all the heat has died away, the cast can be released from the core.  First remove the stop ends, and using a joint rule slowly separate the cast fro the core. When you have separated the two pieces put the cast in a safe dry location , then clean off the core and the process can repeated .  
Plasterwork Decorative Moulding in paperback by David Winchester
Plasterwork Decorative Moulding ine Book by David Winchester
Plastering Books
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