How to Mix Casting Plaster

This is the sixth video in a series of quick coving tips that explain how to install plaster coving and plaster cornice. A professional plaster coving installer explains how to mix casting plaster to the right consistency for filling plaster coving after the fitting stage. 

To do this properly and correctly you’ll need the following tools:

  • Plasterers trowel 
  • Indian bowl 
  • Bucket of clean water.

Step 1 (0:18-0:45):

Fill the Indian Bowl between a quarter and a third full with clean water, take a big handful of casting plaster (Plaster of Paris) and start “knocking it up” (mixing it) with the Small Tool.The correct consistency to aim for is that of single cream. Mix thoroughly making sure everything is mixed off the bottom of the bowl and then let it rest.

Step 2 (0:47:1:10):

Over a period of 5 minutes the mixture will thicken naturally and will be ready to be used when you can pick it up with the Small Tool. 

Step 3 (1:15:1:40):

This mix will be in a usable state for the next 5-7 minutes and then it will become useless, so don’t knock up more casting plaster than you can comfortably use for filling the fitted cornice in that 5-7 minute horizon.