By ShowMeStepByStepPublished Updated
Based on a video by Red Rocking Bird.
Pourable two-part silicone is a different animal to the silicone-caulk putty method. You weigh it, mix it, pour it and let it find its own level, which is what lets it pick up detail a putty press never will.
Red Rocking Bird builds a simple housing, sticks the master pieces to a clear base and fills the space around them. The one thing worth respecting is the weighing - this is a ratio product, and eyeballing it gives you a mold that never fully cures.
10 steps · about 11 minutes.Check off each step as you go and your progress saves automatically.
You need something to cast into. A simple plastic mold housing works, and it does not have to be anything purpose-made.
Whatever you use just needs straight sides and a base you can seal, so the liquid silicone cannot escape.
Run double-sided tape all the way around the rim of the housing, checking there are no gaps in the run.
Some people hot-glue the housing down instead. Tape is enough and it comes apart far more easily afterwards.
Press a sheet of acetate or wide clear tape across the taped rim to close the bottom.
A clear base does two jobs - it seals the housing, and it gives you a sticky surface to mount your master pieces onto.
Tip
Check the seal all the way round before you mix anything. Silicone finds every gap.
Glove up, work somewhere well ventilated and protect your surfaces before you open anything.
Weigh part A and part B out on a digital scale. This is a ratio product, so measuring by eye leaves you with a mold that stays tacky and never fully cures.
Combine the two parts with a wooden stick and keep going. Most kits ask for three to five minutes.
Scrape the sides and the bottom of the cup as you stir. Unmixed streaks left in the corners will not cure.
Tip
A good kit mixes smoothly and pours almost bubble-free, so do not rush this part looking for shortcuts.
Stick the pieces you are moulding down onto the clear base inside the housing.
Pack in as many as the space will take. Silicone is the expensive part, so every gap you leave empty is money poured away.
Tip
Anything hollow will float up once the silicone goes in. Stick those down firmly or weight them.
Pour the mixed silicone into the housing in a thin steady stream from one corner, letting it flow around the masters.
Pouring from height and in a thin stream helps break any bubbles on the way down.
Tip
Leave it clear if you plan to cure UV resin in the finished mold. Pigment blocks the light.
Set the filled housing somewhere genuinely level and leave it for about 24 hours.
A levelling table is ideal but any flat shelf works. Cure it on a slope and the back face of your mold sets at an angle.
Peel the housing away from the cured block and pop the mold out. It should release with gentle pressure - run a knife around the edge only if it sticks.
Flex it open and check the cavity picked up the detail you wanted before you cast anything into it.
Mix your resin, pour it into the new mold and let it set.
A little warmth underneath from a heat pad helps the resin flow into fine detail. Add pigments or embellishments at this stage.
Tip
A silicone mixing cup is worth using for resin - it peels clean once cured and you can reuse it.
Keep going
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LET'S RESIN
LET'S RESIN UV Resin, Crystal Clear (500g)
Low-odor, low-shrink UV resin that cures hard and stays yellow-resistant. Sunlight or a lamp sets it in minutes, so no mixing or 24-hour waits.
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LET'S RESIN Coaster & Keychain Molds (18 pc)
Flexible silicone in the shapes beginners actually make, and they pop out clean and reuse for years. The mold set to start casting with.
LET'S RESIN
LET'S RESIN 36W Two-Sided UV Lamp
Cures faster and more evenly than sunlight, with timer presets so pieces do not over- or under-set. What turns UV resin from fiddly to reliable.
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Quick reference
5 questions, answers, and one-line explanations. Tap to expand.
1.What must the mold housing have?
Answer: Straight sides and a sealed base
The liquid silicone just needs somewhere it cannot escape from.
2.Why fit a clear acetate base across the taped rim?
Answer: It seals and holds masters in place
The clear sheet closes the bottom and gives a sticky surface to mount onto.
3.Why weigh part A and part B on a digital scale?
Answer: It is a ratio product that must be exact
Measuring by eye leaves you a mold that stays tacky and never cures.
4.Why scrape the sides and bottom while stirring?
Answer: Unmixed streaks will not cure
Corners are where the two parts hide from the stirring stick.
5.Why pack in as many masters as the housing will take?
Answer: Silicone is the expensive part
Every empty gap is silicone you paid for and cannot cast into.
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