Mould-making silicone (condensation cure)
Frequently asked questions
Can Mould-making silicone (condensation cure) be laser cut?
No: Mould-making silicone (condensation cure) is not suitable for laser cutting. However, it releases toxic fumes — machining is not recommended.
Can Mould-making silicone (condensation cure) be CNC machined?
No: Mould-making silicone (condensation cure) is not suitable for CNC milling.
Is Mould-making silicone (condensation cure) food safe?
No, Mould-making silicone (condensation cure) is not considered food safe.
Physical properties
| Density | 1050.0–1200.0 kg/m³ |
|---|---|
| Tensile strength | 4.0 MPa |
| Thermal expansion | 280.0 µm/m·K |
| Moisture absorption | Negligible |
Laser processing
Thermal decomposition of condensation-cure silicone releases silicon dioxide (SiO2) dust, highly abrasive to machine optics and irritating to the respiratory tract, plus volatile organic compounds from the stannous catalyst.
CO₂: Not applicable. Produces abrasive SiO2 dust and organic vapours that irreversibly damage the laser optics.
Diode: Not applicable.
Fiber: Not applicable.
CNC / milling processing
Soft elastomer: deforms and tears under the action of rotary tools. Cannot be milled or CNC-cut in a controlled manner.
Post-processing
Sanding: Not sandable: the elastomer bounces against the abrasive. Casting flash must be removed with a sharp scalpel.
Primer: Nothing chemically bonds to cured silicone, except fresh silicone applied in contact with the already-cured surface.
Gluing: Bondable or repairable only with fresh silicone of the same type. Incompatible with cyanoacrylate and epoxy glues without silicone adhesive primer (commercially available but with modest mechanical grip).
Over time: Good stability over time, resistant to UV and moisture. Less durable than platinum silicone under intensive casting cycles: tends to lose flexibility and tear more easily after 30–80 uses, compared to 100–200+ for addition-cure silicone.
Common defects
- Inhibition of epoxy and polyurethane resins cast inside the mould — the tin catalyst migrates and prevents polymerisation; always seal with PVA or a wax layer
- Greater dimensional shrinkage than addition silicone — up to 2–3% vs 0.1–0.5% for platinum; factor in for high-precision applications
- Trapped air bubbles during casting — pour in a thin stream from height
Safety
Recommended PPE: gloves_nitrile
Cured condensation-cure silicone is essentially inert and non-toxic. The liquid components contain organotin catalysts: avoid prolonged skin contact during mixing. Adequate ventilation during liquid pouring.
Availability and formats
Commercial formats: two-part A+B pourable liquid kit, paste (single-component moisture-curing cartridge for sealing)
Related materials
Sources
- Wacker Chemie — Elastosil M4600 Technical Data Sheet
- Smooth-On — Mold Max Series Technical Bulletin
Information on compatibility, processing parameters and safety is purely indicative. MakerSpecs accepts no liability for damage to persons or property arising from the use of this data. Always check the safety rules and the manufacturer's official manuals before carrying out any processing.