Creating a Two-Part Plaster Mold

1. Using petroleum jelly, grease a free-release container appropriate for the size of the object for which you will be making a mold.

2. Grease the object for which you are making a mold (celery root).

3. Make reinforcement fibers by cutting strands of thick hemp rope and unraveling them.

4. Fill a bucket or other medium sized container with water. Gradually add plaster by sprinkling it over the surface of the water--mixing by hand until the plaster sprinkles begin to sit on the surface of the mixture.

 

5. Quickly begin scooping plaster into greased container until plaster coats bottom at least 1" deep. Add some shredded hemp fibers and more plaster until a substantial thickness is reached in proportion to the weight of your mold object. Place object in plaster and begin filling the container with plaster and hemp around the object until it reaches halfway up the object.

6.  Prepare another batch of plaster if necessary to reach halfway up the object. Smooth out the surface but add a nodule on either side of the object. This will create a groove for the two-part mold to lock in place. Let mold set at least 1 hour.

7. Clean up any debris of plaster and smooth out edges and nodules. Be sure no hemp is exposed or your "two-part" mold will not separate.  Grease top of object, plaster, and container well keeping in mind that any deep recesses or protruding fragile appendages may be lost or cause the mold to fail.

8. After at least one hour prepare more hemp strands and make a hemp rope handle by tying off two ends of a piece of hemp rope with enough room in between the knots for a handle. Fray the ends of the rope (beyond the knots) so that the frays can be embedded in the wet plaster.

9. Prepare plaster mixture and coat top of object layering plaster and hemp threads until you reach the top of the container or there is at least 3" of plaster covering the top of the object. Quickly place the handle on top and cover frayed ends with plaster. Let sit at least one hour. Since the activation and setting of plaster is a chemical reaction you can tell if the correct proportions of water to plaster were used if the mixture begins to heat up. If after 30-45 minutes the plaster is still damp to the touch the proportions were not exactly correct and the plaster will remain chalky and the product will be much more fragile.