Molds are used to make many of the objects that we come into contact with on a daily basis. Molds have been in use since the Bronze Age to assist in the production of various items from spearheads, jewelry, toys, plastic bottles and dishes. There are many kinds of mold making materials. In ceramics, plaster is used in the creation of molds because of its ability to absorb water from the clay. Similar to industry, I cast the clay by pouring slip, a specific kind of liquid clay, into the plaster mold. However in my case I am making the original piece the plaster is cast from by hand.
Plaster is a very interesting material. When poured in its liquid state it has the ability to capture the detail of the surface it is poured on to. Since I am pouring clay into the molds, which also retains the surface detail, I end up with a clay piece that mimics the surface of the original or the positive. Clay is commonly used when making a positive but I began to think about different materials that could be used in this process. After becoming interested in the qualities of paper I was given a book on paper folding for designers. I began to generate vessels forms with paper and making molds from these forms. I am interested in keeping the integrity of all the creases and wrinkles that happen naturally in the paper. You can find more of these paper pieces in my shop.
It proved to be a challenge both to create vessel forms from paper and produce a usable mold from the paper positive. Months of trial and error finally produced the pieces you see on this website. I started by figuring out how to fold the paper into a vessel shape. I have been fascinated with soft triangles for years now, so I started out by cutting the paper into a triangle. By altering the shape and proportions equilateral triangle I started out with, I was able to achieve different folded shapes. To begin I measure and cut out the shape I need, then I fold and glue the paper. I use a spray bottle filled with water, rubber bands and sometimes weights to coax the paper positive into the final shape I want.
I give the outside of the paper positive a coat of water resistant varnish. I currently use spray shellac but I am still trying to find a product that will help the paper release from the mold better. After several coats of shellac, I use expanding foam to fill the interior and give the paper the rigidity needed to support the weight of the plaster. This part has been very tricky as the expanding foam can also rip open the seams or disfigure the bottom of the paper original. It is best to add the foam in several stages allowing it to cure in between. I bring the foam pieces inside to cure. In my experience colder temperatures cause the foam to shrink as it cures and consequently pull in the sides of the paper form. However the directions for expanding foam say that you should only use the expanding foam outside. Therefore I do not recommend readers bring or spray the foam indoors
When I first attempted to make the molds, I poured liquid plaster over the paper pieces once the foam inside had cured. This yielded inconsistent results and I switched over to a frosting method. With this method I wait for the plaster to thicken from a liquid to an icing consistency and I slowly build up the plaster around the piece. After the plaster cools and hardens, I clean up the mold and remove the paper positive. I let the mold dry out over the course of a few days. Then it is ready to cast.
If you are interested in a more in-depth discussion of ceramic mold making techniques, I recommend Andrew Martin’s The Essential Guide to Mold Making and Slip Casting as a resource. The paper-folding book I used to generate ideas was Folding Techniques for Designers: From Sheet to Form by Paul Jackson. Of course if you have any questions for me just comment below.
Thanks for reading.