Return to... Cold Mold Powder Separation Mold

• Things you will need:
  • your model
  • Cold Mold Compound
  • mold frame
  • small brush
  • small quantity of mica powder
  • pair of mold plates
  • brass locators
  • mold cutting knife & blades
  • sprue rod and button
  • vulcanizer, clamps, or heavy object
    
    

Step 1. Prepare at least 4 brass locators by folding each of the four prongs on each locator toward the center of the locator. After bending the prongs, press each locator onto a flat surface so that the prongs are all flush with the table surface. Set aside.

Step 2. Weigh equal quantities of Part A (light blue) and Part B (purple) so that when combined, they fill approximately half of your mold frame. It is recommended that the amounts be weighed for accuracy to ensure proper curing of the compound.

Step 3. Rapidly knead together Parts A and B until a uniform color is attained. You have a total working time of approx. 2 minutes, so work quickly. Before proceeding to the next step, be sure that the compound is entirely mixed with no streaks of color. Set aside a small amount of compound to fill the locators (step 4).

Step 4. Working quickly, press the compound into the mold frame making sure that the compound reaches the bottom of the frame (the frame should be on top of one of the mold plates). Position your model in the center of the frame and press it into the compound until the top edge of the model is nearly flush with the surface of the compound.

Step 5. Fill the locators with the compound set aside in step 2. Position one locator at each corner at least 1/8" away from the side walls of the mold frame. Place your sprue button and rod into position, making sure that the sprue rod is at least 1/8" away from the model. Press down half-way. As the compound begins to cure it may be necessary to hold down your model to prevent it from rising above the surface.

Step 6. Lightly brush mica powder over the entire surface of the rubber and blow off any excess powder from the surface. It is not necessary to wait for the compound to cure completely before continuing.

Step 7. Repeat steps 2 and 3, using slightly more compound than is necessary to fill the rest of the mold frame. Again, make sure that the compound is mixed completely. There is no need to set aside compound for the locators.

Step 8. Press the compound into the mold frame. The top of the compound should be slightly above the top edge of the mold frame.

Step 9. Place the second mold plate on top of the mold frame, pressing the plate down with the palm of your hand. Although Cold Mold Compound cures without heat, slight pressure is needed to ensure a good mold. Pressure can be applied to your mold in any one of the following ways:

1. Place the mold frame in a cold vulcanizer and apply pressure until the mold plates touch the top and bottom of the mold frame. This is the preferred method because it applies even pressure over the entire mold frame.
2. Use an adequate number of C-clamps or similar clamps to bring the mold plates into contact with the mold frame.
3. Place a heavy weight, such as several large books, on top of the mold frame.

Step 10. After approximately 30 minutes under pressure the compound should be completely cured and the mold can now be removed from the mold frame. Remove the plates from either side of the frame and push the mold out with your fingers. Using a pair of scissors, remove the excess compound that has extruded between the frame and mold plates.

Step 11. To separate the mold, simply pull the two halves apart. Remove the model from the mold, flexing the mold if necessary.

Step 12. Once the model is removed, gates are cut into both halves of the mold to join the sprue to the model cavity (as shown on the right). Vents can now be cut into the mold to ensure complete filling during wax injection or white metal casting.