1. Into a clean cup, pour 90 g of Ecoflex 10 part A and 90 g Ecoflex 10 part B. The final mixture should therefore weigh 180 g.
2. Using a rigid stirrer (e.g., a tongue depressor), mix the two halves together slowly, to avoid creating air bubbles. Air bubbles, when the silicone has cured, can result in rupturing at lower stresses than you would need the silicone bladder to be able to withstand during inflation.
3. To eliminate any air bubbles, put the mixing cup in a vacuum chamber. Removal of the air just above the surface of the liquid silicone in the cup will draw out any pockets of air under the surface.
4. Coat the interior of the mold halves with a mold release, then let them dry for the appropriate amount of time (generally listed on the side of the mold release can).
5. Pour half of the Ecoflex 10 mixture in each mold half, carefully coating the walls. Ecoflex 10 has a relatively low viscosity, but you should still be able to get some of it all over the interior of the mold. This will help the silicone spread once we put the filled mold on the rotational caster.
6. Carefully fit the mold halves together. While not necessary, it is generally advised that you use some kind of external binding to make sure the halves stay together.
7. Fix the mold on the rotational caster, centering it about the axis of rotation. Depending on your rotational caster, you may have to affix the mold using zip ties, bolts, etc. Your rotational caster should have an approximate 2:1 spin rate. We used 0.77 rotations per second and 1.54 rotations per second. Place the mold vertically, upside down (the bottom part is the cylindrical nozzle) in the caster for 30 seconds. This will spread the silicone.
8. Turn the mold with the nozzle facing down, and put it on the caster using the same settings.
9. Let cure for 2 hours.
10. Take the mold off the rotational caster and place it in the oven at 65 Celsius for 30 minutes.
11. Remove the mold and let it cool down.
12. Open the mold and carefully demold the silicone chamber.
