Soul Cycle Mothership, a molded fiberglass speaker cabinet for bicycles.

Step 7 Create a parting between the left and right of the shape

The clay is used to define the parting line of your shape. In my case the parting line is also the center line. So it was obvious and easy to find. I used a flexible ruler and drew the line on my shape with a sharpie.

The role of the clay is to create a lip upon your parting line, upon which you can build one half of mold, in my case the left. After I built up the left half of the mold, I removed the clay (it separated from the mold and the positive form easily with a careful application of mold-release where needed.)

In the photo you see that I made a special mold-making table for this step. It has a hole slightly large than the positive form that holds it in place so that I can apply the clay, and then the liquid rubber. I used another