Paul taught me a different method of plaster molds. Usually one is taught the “island” technique of plaster mixing. His was the method of weighting the plaster and water.
One of the first materials we worked with to create molds was rubber latex (Rub-R-Mold). This type of mold is great for one part molds, small objects, and ones with complex forms. The valuable characteristic about a rubber latex mold is its ability to be flexible. It can be turned inside out, twisted, popped, and causes no damage to the mold if made properly. This allows for complex forms casted to be removed with ease. Paul had us bring with us small objects that were fairly complex so that we could learn the techniques necessary for mold making. I brought a small pendant and a sculpture of a toro. You can use this with leather hard or bisque ware as well.
We used many different products to create molds and the Silicone Rubber #30 by Smooth-On was very effective. Our first task was to create a plasticine form to create our mold from. We used chip board again to create a barrier for our mold and once poured it took about 6 hrs to cure, but I let it sit overnight.
We used our Silicone Rubber mold to create many types of castings. White Liquid Plastic #300 by Smooth-On was used. We also learned to cast Wax (Paraffin) and Cement (Quikrete.) A neat trick when casting the liquid plastic is to pour water in the mold first so you can determine how much material you may need to mix up. Always use gloves when mixing the plastic! If you plan to paint your plastic you can apply a thin layer of gesso to the surface to help many paints adhere to the surface. You will want a cement with no large particles and no aggregate! If you are creating outdoor sculpture you can add a fortifier to strengthen your cement. Paul stressed that you store your molds together so that the surface inside does not change and that the mold continues to fit together properly.
We created press molds and plaster molds to cast paper pulp. I found the bisque press molds to be more effective than the plaster molds. They seemed to dry out the paper faster, where the plaster castings took much longer to dry. You can also use the latex mold but the moisture must be sponged out since it is not absorbant. Once the paper has dried completely it is surprisingly very durable!
Paper pulp can be created by many materials. You can use paper towel and toilet paper as a cheaper material. We created molds from cotton, denim, and old t-shirts too but those were mixed with the proper machine and technique. The paper towel and toilet paper can be mixed with a basic blender and water.
The paper will only adhere properly if you consider it like clay. The pulp must be of the same consistency and with similar amounts of water for them to bond strongly.
Some References From Paul...