My recent failures with creating a silicone mold have prompted me to dig deeper into the processes of creating a mold of an object to cast in a different material. I'm going to start with the basics:
What is Casting?
A cast is a reproduction of an original item in new material.
Common Materials to cast with:
- Resin
- Plaster
- Plastic
- Wax
- Latex/Rubber/Silicone
- Food (Ice, Chocolate, Hard Candy, etc)
- Molten Metal
Common methods for casting are:
Slip Casting - makes a thin layer, commonly used for latex masks
2-part Cast - Make a mold with 2 halves sandwiched together
Pour Mold - put material into a divot
What is a Mold?
FYI, this didn't work out. |
A "mold" is an imprint of an object that we can pour the material into.
Common materials to make a mold with:
- Plastic
- Silicone/Rubber
- Metal
- Clay
- Plaster
What is a Buck?
A "buck" is what we call the subject of the casting, the original piece, so to speak. Whether you are sculpting something to cast later or have an item, you want to reproduce. The buck can be made from all kinds of materials, but sulfur-free Clay is the most common.
Often times during the mold-making process, the clay buck is destroyed.
☣Precautions: Some of these materials are toxic! ☣
Mixing molds can be messy and can cause skin irritation. Latex can cause an allergic reaction.
Epoxy Resin can be toxic, and it heats up! It's a kind of amazing material but handle with care. Sanding resin without a respirator can be incredibly detrimental to your respiratory and nervous systems!
☝Read all safety instructions included with your materials to make sure you have the appropriate safety gear! (A Dust mask is not enough to protect you from resin dust.)
Costume Usage
The most common use for casting in costume making is accessories. Latex masks and prosthetics are commonly made with a mold. It's also helpful for accessories you need to make multiples of. Instead of sculpting it multiple times, sculpt it once and then reproduce it.
Because molding and casting are unique skills, they can be very marketable. Being able to sell a reproduced item is a model of business.
Things I have learned (that no one told me beforehand)
- This is a MESSY process. And clean-up sucks.
- The success rate will vary based on your experience. There are a lot of variables to get right.
- Secure lightweight bucks! Hot glue, apoxie sculpt, clay and such can hold it in place. Otherwise, it will float in the mold before it cures. Or hey...if it does float, make it work.
- Some mold mixes are more beginner-friendly than others.
- Mold mixes are expensive.
- You can mold 3D-printed objects, but the lines will show up if you don't add a finish and sand things down.
- Use smaller Lego blocks if you are making a box, Duplo-style blocks have bigger gaps that can leak. You may still need to seal some of the bricks though.
- Tupperware makes for a good mold container.
- PVC board and hot glue or a sulfur-free clay base is the way to go. A lego base doesn't cut it.
- You can use hot glue, construction silicone, polymer clay, or plasticine as an alternative to specialized mold-making materials.
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