Silicone for acrylic resin molds Water-based acrylic resin, such as A1 acrylic resin (Acrylic One) and Jesmonite, is one of the friendliest materials to cast in a silicone mold. It contains no solvents or isocyanates that attack silicone, and the resin doesn't stick to silicone. So the life of your...
Silicone for Acrylic Resin Molds | Acrylic One (A1) & Jesmonite (20)
Silicone for acrylic resin molds
Water-based acrylic resin, such as A1 acrylic resin (Acrylic One) and Jesmonite, is one of the friendliest materials to cast in a silicone mold. It contains no solvents or isocyanates that attack silicone, and the resin doesn't stick to silicone. So the life of your mold is mainly determined by something else: the tear strength of the silicone and how you build the mold. Acrylic resin contains mineral fillers and is often laminated in thin layers with glass fibre. That calls for a mold that can be demolded often without tearing and that keeps its shape.
- ✓ Suitable for A1 acrylic resin (Acrylic One), Jesmonite and similar acrylic composites
- ✓ Usually no release agent needed
- ✓ Tin and platinum silicones from Shore A 5 to 40
- ✓ For terrazzo, coasters, bowls, planters, ornaments and sculptures
Which silicone should you choose for acrylic resin?
Condensation or addition cure
Condensation cure silicones (tin) are economical, not sensitive to cure inhibition and therefore a good choice for most acrylic resin molds. They shrink slightly more (0.2 to 0.4%) and become stiffer after long storage. Addition cure silicones (platinum) are low shrink, cure faster and remain stable for years. Choose platinum when dimensional accuracy matters, for example coasters and tiles that must fit exactly, or when you want to keep the mold for a long time. With platinum, watch out for cure inhibition from sulfur-based clay, latex and some 3D prints on your model.
Hardness
- → Shore A 5 to 15: very flexible, for deep undercuts and delicate details. Use a support shell, or the mold will deform under the weight of the resin.
- → Shore A 20 to 30: the all-round choice for terrazzo, bowls, coasters and ornaments.
- → Shore A 35 to 40: firm and dimensionally stable, for flat products, tiles and large molds without undercuts.
Our silicones for acrylic resin
Condensation cure silicones
- Silicone Condensation 20 Universal: our economical all-rounder for acrylic resin, plaster and concrete.
- Silicone Condensation 5 and Condensation 35 with catalyst B 5: the same range in soft and firm.
- Dow Silastic RTV 3481 R and RTV 3481 Fast: Shore A 19 and 23, high tear strength and excellent release. Also available to private customers.
Addition cure silicones
- Wacker Cenusil M 810 Pink 10: Shore A 10, soft and flexible for undercuts and fine details.
- Silicone Addition Yellow 25 and Green 30: 1:1, our platinum all-rounders for terrazzo, bowls and ornaments.
- Silicone Addition Clear 25: Shore A 25, 1:1, low viscosity and tear resistant. The clear mold lets you see air bubbles and place terrazzo chips precisely.
- Wacker Elastosil Vario 15 and Vario 40: translucent, hardness adjustable between Shore A 15 and 40 by blending the two. Also available as Vario 15 Fast and Vario 40 Fast.
- Wacker Cenusil M 825: Shore A 25, 1:1, free flowing for molds with deep undercuts.
- Polytek PlatSil FS-10 and FS-20: 1:1, demold after about 25 minutes. Handy when you quickly need an extra mold.
- Zhermack ZA 13 Mould, ZA 22 Mould and HT 33: 1:1, developed by Zhermack for plaster, concrete and cast stone, and therefore also suited to mineral-filled acrylic resin.
Jesmonite or A1 acrylic resin?
All silicones on this page are suitable for Jesmonite. We work with A1 acrylic resin (Acrylic One) ourselves, a water-based acrylic composite that is processed the same way: mix powder and liquid, then cast or laminate.
Advantages of A1 acrylic resin
- ✓ Available directly from our stock, together with the silicone for your mold
- ✓ A complete system with pigments, fillers and additives, glass fibre and sealer
- ✓ Solvent free, suitable for indoor and outdoor use
- ✓ Advice from our own team on mold and material
Points to note
- → A1 has a different mix ratio than you may be used to with Jesmonite. Always follow the A1 processing instructions, not a Jesmonite recipe.
- → Videos and forums show more examples with Jesmonite than with A1. The method is largely the same, but test a new recipe on a small scale first.
Tips for acrylic resin in a silicone mold
- → Let the silicone cure fully before the first pour.
- → When laminating, apply a thin gel coat first so all details are filled, then build up with glass fibre.
- → Use a support shell of plaster or acrylic resin for large or soft molds so the mold doesn't sag.
- → Use a mold box for an even mold wall thickness.
- → Clean the mold with water after use and let it dry thoroughly.
Frequently asked questions
Can I cast acrylic resin in any silicone mold?
In principle yes, water-based acrylic resin doesn't attack silicone. The difference lies in tear strength and hardness. A soft silicone with low tear strength wears out faster when demolded often.
Do I need a release agent?
Usually not. Acrylic resin doesn't stick to silicone. A release agent can help with very deep undercuts or a new mold that still feels grippy.
Which silicone is best for terrazzo and coasters?
A silicone of Shore A 20 to 30, such as Yellow 25, Clear 25 or Condensation 20 Universal. For flat tiles that must be dimensionally accurate, choose platinum.
Do these silicones also work for plaster?
Yes. For plaster and porcelain plaster we have a separate page with tips: silicone for plaster and porcelain plaster.
Related categories
- A1 acrylic resin (Acrylic One) and accessories
- Silicone for plaster and porcelain plaster
- Silicone for concrete molds
- DIY terrazzo kits
- Silicone for production molds
Advice for your acrylic resin mold
Tell us what you want to make, how large the model is and how many castings you need. We will then recommend the silicone that fits best. Email info@siliconesandmore.com.