Mold Making: Two Part Silicone Mold

Step 3 Inscribe a key

For most organically shaped parts like action figures or prosthetics, your mold will fit together in a very specific way. The seam line that these organic shapes have just naturally locks together in one position. For more geometric or mechanical parts like legos or usb drives, your mold seam may be nearly flat, and therefore difficult to align or register. To make sure the mold goes together the same way each time, you add a seam line or a key to the mold. I prefer to make a quarter inch trench along the border of the part, not only to fit it together well each time but to also prevent material from leaking out when I'm casting the final parts.