Silicone Molding

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Wacker Elastosil M 4601 part A and B


Wacker Elastosil M 4601 part A and B Note: Part A is the big white container and part B is the small container containing red chemical. (Refer to the image on the right)


  • Mixing ratio (by weight) A/B 9 : 1 - very important to be accurate otherwise the cured part will be weak
  • Curing time - approx: 12h at 22°C / approx: 30min at 70°C


Wear safety goggles, lab coat and gloves.

  • In case of skin contact: wipe off the excess material with cloth or paper. Wash with soap and water. (If possible, use a waterless hand cleaner to remove as much material as possible )
  • In case of eye contact: immediately flush eyes with water for 15 minutes.


  • Do not flush away the remaining with water. However after the silicon has hardened, you can dispose it off in the bin.



Mold for UiO logo
  • Mold (Sample mold shown in image)
  • Calculator
  • Disposable plastic mixing container
  • Disposable plastic fork/knife
  • Analytical balance
  • Disposable syringe


  1. Put the empty mixing container on the scale and press the tare button to reset the scale.
  2. Pour silicone part A (big white container) inside the empty mixing container (placed on analytical scale) leaving room for part B (small container with red colored chemical).
  3. Using the weight measured in step 2, calculate the weight for part B using B = A/9 formula.
  4. Press the tare button and pour in part B until the weight is right. (Note: steps 2-4 can be replaced by measuring the amount of chemicals required using a plastic disposable syringe).
  5. Mix it well – it is important to scrape the walls and bottom of the mixing container thoroughly. Always mix using a figure of 8 to prevent air in the mixture. For better results or critically high-quality parts, pour the mixture into a second container.
  6. Pour the mixed silicone in the casting mold.
  7. Let it hardened over night or atleast 12 hours.
Silicon molded UiO logo

To Consider

Mirroring mold

If the mold is similar to the sample mold containing text/image. Make sure to mirror before 3D printing the mold.

Viscosity challenges

Silicone wall thickness less than 3mm can be difficult to make as the liquid silicone will stick to the walls, and not float freely as you want It can be impossible to pour silicone into holes less than ca. 8mm in diameter. It may help to print a funnel over the hole.

NB1: During the curing process air bubbles will generate and float up to the surface.

NB2: It is also possible to de-air it in the vacuum chamber. The silicone volume may rise up to 5 times the original volume in the vacuum chamber so either use a large enough cup or de-air in more than 1 go.

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