The past couple of week, I have been working with a new (to me) product called Jesmonite. It is a gypsum-based acrylic resin compound that, like other resins, accepts fiberglass reinforcement to provide strength and stability, and best of all is water-based– so no messy chemical cleanup. I purchased AC-300, which is rated for long term indoor use and brief outdoor use, and is also much less expensive than the other mixtures. It hardens quickly and with reinforcement, becomes very sturdy.
The procedure is fairly simple. Since I have open molds, I am making a fiberglass laminate rather than a solid piece. There are basically 3 layers of Jesmonite in the laminate along with two of woven fiberglass. The first layer is plain Jesmonite, laid in with a paintbrush. This is called the gel coat and will become the exterior layer. Next, while the gel coat is still tacky, you place in a layer of woven fiberglass. The next layer is Jesmonite mixed with chopped fiberglass strands, then another layer of woven fiberglass. Finally another layer of plain Jesmonite is painted in on top of that.
Like other resin products, you can add pigment to color the Jesmonite or you can add other fillers to try to simulate different materials, or you can paint the final result. My intention was to use powdered metals to simulate cast metal; this process is called “cold casting” since you don’t need to heat the metal. Other available materials include granite, marble and sandstone. AllScot, the company from whom I purchased the Jesmonite, had several powdered metals to choose from and being the skinflint that I am, I bought the least expensive, iron and aluminum.
So far I made three casts using Jesmonite and have been generally pleased with the outcome. My initial cast was done in order to get a feel for the process. This came out pretty well, although some areas failed to cast due to air pockets. This was operator error, though and not a fault of the Jesmonite. My next two, I attempted to use the metal powders. I adjusted the proportions according to the instructions, but the Jesmonite was quite thick this time and I practically had to trowel it into the mold, rather than paint it. The final results were not quite what I wanted; upon reading further I discovered that the AC300, although it will work with the metal powders, it has a lower resin content than the others (hence the cheaper price) and therefore does not achieve the same effect.
I then ordered some pigments and am hoping to get those casts underway this week.
In the meantime, I have sculpted and am molding one more piece and should have that completed this week as well, giving me a total of three masks for this semester.
Below are some photos of my first attempts working with Jesmonite. The blocks in the foreground are hot-melt vinyl which I am using to mold the latest mask. More on that later.