Silicone for Production Molds and Mold Making

Silicone for production molds and mold making

A production mold doesn't have to be good once, it has to be good a hundred times. In serial production of decorative stones, ornaments, facade elements, prototypes or technical parts, three things matter: tear strength, dimensional accuracy and resistance to the casting material. This collection brings together the professional mold making silicones that hold up to that, from Wacker Elastosil, Polytek PlatSil, Zhermack, CHT and Dow Silastic.

• ✓ High tear strength for molds with undercuts that are demolded often
• ✓ Low shrink platinum silicones for dimensionally accurate reproductions
• ✓ Hardness from Shore A 13 to 70, from flexible molds to rigid tooling
• ✓ Suitable for plaster, concrete, cast stone, casting resins, wax and low melting metals
• ✓ Bulk packaging for business customers and advice on choosing the right grade

Addition or condensation cure: which to choose for a production mold?

Chemical difference

Addition cure silicones (platinum) cure without by-products. As a result they shrink less than 0.1% and remain stable for years. Condensation cure silicones (tin) release alcohol while curing and shrink 0.2 to 0.4%. For dimensionally accurate tooling and long runs, platinum is therefore usually the first choice.

Resistance and cure inhibition

Platinum silicones are sensitive to cure inhibition by sulfur, latex, tin and some 3D prints: the silicone then fails to cure on the model. Condensation silicones don't have this issue and in practice are often robust against aggressive resins such as polyester and polyurethane. Unsure about your model? Run a small test first.

Mix ratio

Platinum silicones usually mix 1:1 or 10:1 by weight, and that ratio must be exact. Condensation silicones use a small percentage of catalyst, such as 100:3 or 100:5. Always weigh on a digital scale, never by volume.

Platinum silicones for production molds

Wacker Elastosil and Cenusil

• Wacker Elastosil M 4601: Shore A 28, reddish brown, 9:1, tear strength 30 N/mm. Low shrink all-rounder for reproduction molds.
• Wacker Elastosil M 4630: Shore A 28, white, 10:1, tear strength 30 N/mm. Widely used for concrete molds and casting resins.
• Wacker Cenusil M 825: Shore A 25, 1:1, free flowing. Suited to concrete molds and reproduction molds with deep undercuts.
• Wacker Elastosil RT 625: Shore A 25, translucent, tear strength 30 N/mm. A flexible mold that lets you follow the pour.
• Wacker Elastosil M 4644: Shore A 40, transparent, for vacuum casting and rapid tooling with a long mold life.
• Wacker Elastosil M 4670: Shore A 55, beige, 10:1. Rigid mold for accurate reproductions in casting resins. Fairly viscous, so vacuum degassing is recommended.
• Wacker Elastosil M 4370: Shore A 55, heat resistant, for rigid reproduction molds and casting low melting metals.
• Wacker Elastosil C 1200: Shore A 25, for reusable vacuum bags in composite manufacturing.

Polytek PlatSil

• PlatSil HTS-25 and PlatSil HTS-40: very high tear strength and elongation, developed for production molds that must survive many castings.
• PlatSil FS-10 and PlatSil FS-20: 1:1, demold after about 25 minutes. Ideal when you quickly need an extra mold to scale up production.
• Looking for PlatSil 73-40 or the tin silicones in Polytek's TinSil range? We supply these on request through Silicones and More.

Zhermack

• Zhermack ZA 13 Mould WT 45: Shore A 13, translucent, 1:1, long working time. Soft mold for concrete, plaster and cast stone with fine detail.
• Zhermack ZA 10 Orange: Shore A 13, 1:1, fast demold. Also listed by Zhermack for polyurethane.
• Zhermack ZA 22 Mould: Shore A 22, blue, 1:1, tear strength 20 N/mm. The middle ground for concrete and cast stone molds.
• Zhermack HT 33 Translucent: Shore A 33, 1:1, for firmer molds that keep their shape with larger castings.
• Zhermack HT 45 Translucent: Shore A 45, 1:1, for tooling and prototypes where dimensional stability comes first.
• Casting polyurethane in series? Zhermack offers ZA 43 PU and XTX 45 Oil Bleeding for this. We supply both on request.

CHT

• CHT QM 270: Shore A 62, 10:1, heat resistant up to about 200 °C. Rigid tooling for architectural reproductions, furniture and frame moldings.
• The hard casting silicones CHT QM 262 (Shore A 60, blue) and QM 272 (Shore A 70) for rubber rollers and concrete molds are also available on request.

Condensation cure silicones for production molds

• Dow Silastic RTV 3481 R: Shore A 19, tear strength 26 N/mm, excellent release. Robust against polyester and polyurethane. Also available as RTV 3481 Fast for shorter cycle times.
• Wacker Elastosil M 4514: Shore A 25, for molds for polyester, plaster, concrete, cast stone and wax. The catalyst determines what the mold is best suited for.
• Wacker Elastosil M 4440: Shore A 37, economical mold for simple shapes with few undercuts.
• Wacker Elastosil M 4470 with T 40: Shore A 60, stiff and heat resistant, for molds for tin and zamak.

Private or business? Wacker's tin catalysts are subject to European REACH restrictions and can only be ordered by business customers. The Dow RTV 3481 sets are also available to private customers.

Tips for a long mold life

• → Degas the mixed silicone under vacuum, especially viscous grades above 20,000 mPa·s.
• → Let the mold cure fully before the first pour, even if it can be demolded earlier.
• → Use a release agent with casting resins and concrete.
• → Build large molds as a thin skin with a support shell. This saves silicone and keeps the mold dimensionally stable.
• → Use a mold box so the wall thickness is even everywhere.
• → For large quantities, rotate between several molds so each mold can cool down and rest.

Frequently asked questions

How many castings can I get from a silicone production mold?
That mainly depends on the casting material. With plaster, concrete and wax a good mold lasts hundreds of castings. With polyester, polyurethane and epoxy the surface is gradually attacked and the number is lower. A silicone with high tear strength and a release agent extend mold life.

Which hardness should I choose for a production mold?
Soft silicones up to Shore A 20 demold easily from deep undercuts. Shore A 25 to 35 is the all-round choice. From Shore A 40 the mold keeps its shape with large or heavy castings and in vacuum casting.

Can I have silicone custom formulated or a mold made for me?
Yes. We adjust hardness, color and working time through custom RTV-2 silicone. Prefer to outsource the mold? Ask about our custom molds.

Can I order CHT, Polytek or Zhermack products that are not in the webshop?
Yes. Contact us and we will source the product for you and supply it through Silicones and More.

Related categories

• Silicone for concrete molds and WetCast molds for precast concrete
• Silicone for plaster and porcelain plaster
• Silicone for polyurethane, epoxy and polyester
• Rapid prototyping and polyurethane casting rubber as an alternative to silicone
• All premium silicone brands

Advice for your production mold

Tell us what you are casting, how many pieces you need and how large the model is. We will then recommend the silicone that best fits your production. Email info@siliconesandmore.com.