Handling the Model
A silicone mould is a versatile solution when you want to make moulds for applications such as epoxy, concrete, plaster, resin or candle casting. In this guide, we go through silicone mould making step by step, including one-part moulds, two-part moulds and moulds supported with a hard shell.
Mold silicones usually release easily from various materials. However, the model should be gently cleaned from dirt, oils, dust, etc., for example with acetone. If there are cracks or uneven areas you don’t want copied, fill and smooth them. Porous surfaces should be sealed. Materials like plastilina or beeswax may inhibit silicone curing and should be sealed with varnish.
Silicone can chemically bond with certain materials such as silicone itself, glass or porcelain. If needed, a release agent like petroleum jelly can be used.
The model’s surface color may change due to silicone, so testing before mold making is recommended.
Making the Mold Silicone
1. Mix parts A and B thoroughly in their original containers, scraping the bottom and sides.
2. Measure parts A and B in a 1:1 ratio. Kevra’s addition-cure silicones include Mold Silicone 1520, 1540, and 623.
3. Mix parts thoroughly, bottom and edges included. Poor mixing can cause uneven curing.
4. Mixing introduces air bubbles. These can be removed with vacuum (10–20 mbar). Note that silicone expands in vacuum. Without a vacuum, gentle stirring or pouring from a wide container edge can reduce bubbles.
One-piece silicone mold
1. Clean the model thoroughly and if needed, seal any porous or delicate surfaces.
2. Position the model in a mold box (container) so that there is at least 2 cm of space around all sides and on top.
3. For improved surface detail and to prevent air bubbles on the model’s surface, apply a thin coat of silicone with a brush before pouring.
4. Kaada silikoni tasaisesti ja hitaasti laatikkoon, niin että sen pinta on vähintään 1 cm mallin yläpuolella.
5. Kun silikoni on kovettunut, poista se laatikosta ja irrota mallista.
6. Silikonimuotti on valmis käytettäväksi.
Two-Part Silicone Mold
Planning is key for a two-part mold.
1. Puhdista ja käsittele tarvittaessa malli
2. Mark the model roughly halfway. Protect one half with plastic wrap or foil.
3. Aseta laatikon pohjalle esim. plastisiinia ja paina malli siihen merkkiin asti. Paina kohdistusreiät plastisiiniin.
Plastisiini voi estää silikonin kovettumisen joten pinta tulee suojata lakalla/muovikalvolla yms.
4. Sivele mallin pinta tarvittaessa silikonilla ilmakuplien ehkäisemiseksi.
5. Kaada silikoni tasaisesti ja hitaasti laatikkoon, niin että sen pinta on vähintään 1 cm mallin yläpuolella.
6. After curing, remove silicone from the box without detaching from the model. Flip the mold and model in the box.
7. Treat all surfaces with a release agent like 10% Fairy liquid solution (dish soap), as silicone sticks to silicone.
8. Brush silicone again if needed and pour at least 1 cm over the model.
9. Anna silikonin kuivua ja irrota osat toisistaan.
10. If you haven’t pre-made any pouring or air vent holes in the mold, you can drill them now. An air vent is necessary to ensure that the casting material spreads evenly throughout the mold.
11. Join mold halves with tape or straps before casting.
Mold with Hard Support Shell
1. Protect the model surface with plastic wrap or foil and place it in a box (box sides should be removable and can be fixed with Plasticine).
2. Apply approx. 1 cm thick Plasticine layer on model surface. A protective film can be added.
3. Pour plaster or similar over the model. Ensure at least 3 cm of plaster around. (The shell can also be made with fiberglass and epoxy/polyester laminate instead of a box.)
4. Separate parts and remove Plastilina and protective film from model.
5. Drill pouring and air vent holes in the hard shell. Pour holes must be lower than vent holes. Clean the inside of the shell from dust and dirt. Plasticine residue can prevent silicone curing.
6. Place the model and shell back into the box. Ensure that the shell is positioned correctly. Prepare silicone and pour from the pouring hole until silicone appears in the vent hole.
7. Let silicone cure and remove mold from box and model. Mold is now ready to use.
Need supplies for silicone mould making? Explore our mould-making silicones and choose the right silicone for making your own silicone mould.