R PRO 20 - Silicone rubber 1:1 for medium hardness moulds, making kit for DIY

In accordance with Regulation No. 1272/2008 (CLP), the product is not classified as hazardous.

Medium hardness silicone rubber for molds

R Pro 20 is a liquid silicone rubber for addition curing, meaning it requires mixing of two components—a base and a catalyst—to cure. This blue rubber is odorless and suitable for both professional and hobby use because it's safe and easy to handle, thanks to its platinum catalyst, which makes it completely safe.

Thanks to its low viscosity and high elasticity, the R Pro 20 casting silicone rubber allows for the creation of medium hardness molds, faithfully reproducing even the smallest details without any air bubbles. It also has excellent resistance to high temperatures and outstanding release properties.

R Pro 20 is a silicone rubber with a Shore A hardness of 21, making it particularly elastic and giving it superior technical and mechanical performance compared to other rubbers. It also has excellent dimensional stability, with a linear shrinkage of 0%, meaning the mold retains its original dimensions over time and resists aging.

How to use medium hardness silicone rubber for molds

To use R Pro 20 silicone rubber, mix component A (base) and component B (catalyst) in equal parts until a uniform color is achieved. The mixing ratio is 1:1 (e.g., 100g of base A and 100g of catalyst B). Weigh both parts and place them into a clean, dry, grease-free container, then mix for about 1 minute, making sure to scrape the bottom and sides of the container.

It's important to follow the recommended proportions to ensure the final product’s properties. Pour the mixed silicone into a mold from a height of 20–30 cm and from the same point to help break air bubbles formed during mixing.

The working time (WT), i.e. the time available to pour the mixed material, is about 40 minutes from the start of mixing, and curing takes about 3 hours at 23°C (higher temperatures speed up curing, lower temperatures slow it down).

After 3 hours, you can demold the model from the medium hardness rubber mold.

If the amount of liquid silicone rubber used is less than needed to complete the mold, you can add more silicone within 24 hours. The second layer will bond with the first one without compromising the final result.

Liquid silicone rubber for soft molds R Pro 20: usage tips

The use of R Pro 20 liquid rubber is recommended for making detailed medium hardness molds.

R Pro 20 rubber is not suitable for matrices containing sulfur or plastiline, as these inhibit the curing process. In such cases, use R15. For hard molds, use R PRO 30. For softer molds, we recommend R PRO 10.