Plaster of Paris ground

Plaster of Paris is produced by the grinding of gypsum and subsequent heating to 150C to get rid of water. For this recipe, any plaster without additives {resins} can be used.

The recipe:
  1. Put a measure of plaster in a pot. Keep adding water, while vigorously stirring, until you get a milky solution. The large amount of water will prevent the gypsum from setting.
  2. Keep stirring for about an hour.
  3. Stir /or shake/ every other hour for a whole day.
  4. Stir /or shake/ once a day for a whole week.
  5. If necessary, add more water so that it stays withing the consistency of, somewhat creamy, milk.

You have now prepared the ground solution. The remaining plaster can be left in the jar or allowed to dry to be used on the next instrument. If left dry, just add some water before using it again.

Application:
  1. Put the milk first on the back of the violin, using a brush.
  2. Before it sets, wipe off with a towel trying to remove as much as possible rubbing it at the same time into the pores. Great care should be taken especially with the edges of the plates and the areas of the scroll where most of the end grain is.
  3. Let it dry. Don`t be alarmed at the plaster-like looks of the instrument at this point.
  4. Take your colorless oil varnish. It should be of the viscosity of honey. Apply a patch of this varnish, the size of a quarter of the plate, with your brush, on the back plate. Right away, wipe off all the excessive varnish with a cloth so that a silky smooth surface of the color of honey remains. Move onto the next section.
  5. When you are finished with the back plate, you can expose the new ground to UV for about ten minutes to harden it. Or if you have a varnishing cradle, just continue on the front plate.
  6. Continue to the front panel, then ribs, then the pegbox and scroll. Work in small sections so that you can wipe off the varnish before it sets.
  7. If necessary, apply to difficult end grain parts more gypsum and wipe off again, repeating the whole process {including varnishing} where needed. The whole surface of the instrument must be sealed having that silky sheen.
  8. Put in your UV box or out in the sun and let dry thoroughly.

Special thanks to the Roger Hargrave for the recipe and application.

Category: Varnishing