Premium condensation hardener for professional mold making and reproduction applications

Wacker Catalyst T 51 is the standard hardener (B-component) for the condensation-curing ELASTOSIL® M silicone rubbers, such as Elastosil M 4511, M 4512, M 4514, and M 4541. This reddish-brown, low-viscosity catalyst based on an organotin compound and silicic acid ester has a density of 0.92 g/cm³ and a dynamic viscosity of 50 mPa·s at 23 °C. T 51 is specifically optimized for excellent chemical resistance to polyester resins, significantly extending the mold's lifespan. The standard dosage is 5 weight percent of the A-component (100:5 ratio). Less hardener extends the pot life and demolding time and allows air bubbles more time to escape; more hardener accelerates curing but increases shrinkage and mold aging. At a 5% dosage with Elastosil M 4514, the pot life is approximately 60 to 90 minutes and the demolding time is 8 to 12 hours at 23 °C and 50% relative humidity.

Key Benefits

• Dosage 5% (100:5) – fixed, easy-to-measure weight ratio to the A-component for reliable curing.
• Density 0.92 g/cm³ and viscosity 50 mPa·s – low-viscosity, mixes quickly and evenly with the base component.
• Excellent polyester resistance – significantly extends mold life when casting polyester resins.
• Mixable with Catalyst T 47 – pot life and demolding time precisely adjustable; at 95:5 (T 51 : T 47), the pot life drops to approximately 30 minutes, and the mold can be demolded after about 4 hours.
• Reddish-brown color – provides visual mixing control, so you can see when the hardener is evenly distributed.
• Long shelf life – stable storage, even in larger quantities, if stored dry and cool.

Typical Applications

• Hardening of Elastosil M 4511, M 4512, M 4514, and M 4541 condensation silicones.
• Mold making for casting polyester resins.
• Reproduction molds for plaster, concrete, and artificial stone.
• Molds for wax, candles, and low-melting metal alloys.
• Mixing with Catalyst T 47 for accelerated curing in time-critical production.

Processing Instructions

1. Stir the condensation silicone (A-component) thoroughly before use to distribute any sedimentation.
2. Weigh the hardener at 5% of the A-component's weight, so 5 grams of T 51 per 100 grams of silicone. You can use 0.5% less or more: less extends curing (more time for de-aeration), more accelerates it but increases shrinkage. Never use too little hardener, otherwise the silicone will not cure (properly).
3. For faster curing, you can mix T 51 with Catalyst T 47, for example, in a 95:5 ratio (per 100 grams of A: 4.75 grams of T 51 with 0.25 grams of T 47).
4. Mix the hardener carefully and evenly into the silicone until the color is uniform.
5. Process the mixture within the pot life and never prepare more than you can process within that time.
6. Wait until the mixture is fully cured before demolding.

Note: pot life (working time) and demolding time are highly dependent on the mixing ratio and humidity. With more hardener or higher humidity, both pot life and demolding time will be shorter. Below 40% relative humidity, the silicone surface may remain tacky; in this case, increase the humidity in the room.

Wacker Chemie AG is a global market leader in the development and production of silicones for industrial and technical applications.

Shelf life: if stored in sealed packaging, dry and cool, the shelf life is at least the period stated on the label. Exceeding this does not automatically render the product unusable; check its properties before use.

This product is intended for the business market. For larger quantities or customized products, please contact us at info@nedform.com or +31 (0)46-3030989.

Professional Support

Are you unsure about the correct dosage or mixing with T 47 for faster curing? Our specialists are happy to advise you on the best hardener combination for your application. Feel free to contact us.