PlatSil FS-20 -Platinum Silicone-

PlatSil FS-20 is a translucent platinum (addition) silicone with Shore A20 hardness, formulated to deliver exceptional tear resistance with a fast 25-minute cure. Its equal-parts mix ratio by weight and volume (1A:1B) and its naturally thixotropic behaviour before gelling make it equally suitable for direct casting and brush application without sagging.

Technical specifications

What it's used for

FS-20 is designed for situations where you need a mould ready in the shortest possible time without sacrificing any durability. Its translucency once cured makes it easy to visually locate the model inside the mould and mark parting lines with precision. You can use it directly as a casting silicone or thicken it with PlatThix to brush it onto moulds of bulky pieces.

• Casting moulds for reproducing decorative, industrial and artistic pieces
• Brush-applied moulds for large objects or complex low-relief surfaces, thickened with PlatThix
• Moulds requiring post-cure cutting, thanks to its translucency
• Reproduction of fine textures and high-resolution surface details
• Difficult demoulding situations where tear resistance is critical
• Production run moulds thanks to its fast cure cycle
• Rapid prototyping requiring reduced time between casting and demoulding

How to use it

1. Prepare the model: make sure it is free of inhibiting contaminants (sulphur, latex, epoxy, freshly cured polyester). Apply a release agent if the model material requires it.
2. Weigh or measure the two components in a 1A:1B ratio, either by weight or by volume. For small quantities, a precision scale is more reliable.
3. Mix component A with component B for at least 2 minutes, scraping the sides and bottom of the container thoroughly to ensure a homogeneous mix.
4. If you need a thicker consistency for brush application, add PlatThix at this point and mix again until evenly distributed.
5. Pour the silicone slowly in a thin stream over the lowest point of the mould so the material rises while displacing air, or brush it on if you have added thickener.
6. You have approximately 8 minutes of working time at 23 °C. Work efficiently but without rushing.
7. Allow to cure at room temperature for 25 minutes. Do not force demoulding before the cure time is complete.
8. Demould carefully. The high tear resistance of FS-20 allows the mould to be stretched during difficult demoulding without tearing.

Usage tips

Control temperature to manage working time

At 23 °C you have 8 minutes of working time, which is sufficient for medium-sized moulds. If you need more time for large or complex pieces, work in a cooler environment (below 20 °C) to slightly slow the reaction. Heat accelerates the cure and reduces the available time. Never add more than 3% of a compatible retarder; exceeding that proportion can ruin the silicone.

Use the translucency to cut moulds with precision

Once cured, FS-20 is translucent: you can see the model inside the mould. This is especially useful when you need to cut the mould to extract the piece. Mark the parting lines on the outside with a marker pen before cutting, aligning the cut with the thinnest points of the mould wall to ensure a clean and repeatable opening.

Inhibition test before you start

If you are going to mould over a material you are not familiar with, cure a small amount of FS-20 directly on that material for 30 minutes. If the result is tacky or fails to gel, the material is inhibiting and you need to seal it (shellac, compatible acrylic varnish) or replace it. This step saves you wasting an entire batch of silicone.

Frequently asked questions