Foam rubber is used in many applications, including make-up prosthetics, puppet bodies, toys, body suits and fantasy costumes. Manufacturing foam rubber is tricky because the components must be mixed, whipped and poured into a mould or pan before being baked to vulcanise the rubber. Foam rubber is very sensitive to temperature and humidity, and often fails to come out right if conditions during preparation and vulcanisation aren't perfect.
- Skill level:
Things you need
- Mold or pan
- Mold release
- Paint brushes
- Mixer and bowl
- Foam latex base
- Foaming agent
- Curing agent
- Gelling agent
- Separate cup
- Foam oven
Establish the room temperature and humidity as close to 20.6 to 22.2 degrees Celsius and 45 to 55 per cent, respectively, as possible.
Coat the mould or pan with a mould release agent. Stearic acid paste is often used. It is brushed in and allowed to dry. The excess is buffed out.
Set a mixing bowl on a scale. After resetting the weight to zero, add 150 grams of foam latex base; 30 grams of foaming agent, which causes the latex to froth when whipped; and 15 grams of curing agent, which vulcanises the rubber when baked.
Put 12 grams of gelling agent into a separate cup. Gelling agent causes the liquid foam latex to gel into a semi-solid state, allowing you to transport it to the oven.
Mix the foam latex. Different brands have different mixing instructions that should be followed carefully, but there are four main mixing stages. The mix stage, which is typically speed setting one for 1 minute, the components are simply blended. Whip is typically done on maximum speed for 3 to 4 minutes. This froths the latex into a meringue-like foam. Refine is typically done on speed setting four for 4 to 6 minutes. This stage begins to break any air bubbles that were incorporated during the Whip stage. Ultra Refine is typically done on speed setting one for 3 to 5 minutes. This stage further breaks down air bubbles, producing a smooth consistency to the foam latex.
Drizzle the gelling agent into the foam latex at the end of the Ultra-Refine stage, taking 30 seconds to complete the task. Allow the mixer to run for another 30 to 60 seconds to fully mix the gelling agent.
Pour or brush the foam into the mould or pan. You must work quickly, the foam will typically gel in 3 to 5 minutes. At the same time, you must be gentle to keep the foam soft.
Allow the foam to gel. Use the foam left in the bowl to test. When you can poke it with a finger and it stays indented -- as opposed to sticking to your finger -- it is ready.
Put the mould or pan in a foam oven and bake it at 82.2 degrees Cor 2 to 3 hours for exposed foam (such as in a pan) and 3 to 5 for foam encased in a mould.
Tips and warnings
- Grams can be converted to ounces: 150g equals 14997gr; 30g equals 2977gr; 15g equals 1503gr; and 12g equals 1191gr
- Foam latex kits can be purchased from a number of manufacturers. Expect your first few batches to go wrong and shop accordingly.
- Foam latex is typically made in a Sunbeam Mixmaster because you can turn the bowl backward to help things mix (called backbowling).
- Do not bake foam latex in a kitchen oven. It releases sulphur fumes that will affect the taste of food prepared in the oven for a long time.
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