PlatSil 73-15 -Platinum Silicone-

PlatSil 73-15 is a two-component, translucent platinum (addition) silicone with a low Shore A15 hardness, mixing in equal parts (1A:1B by weight or volume). Developed by Polytek, it offers exceptional detail reproduction, virtually negligible shrinkage, and a flexible, durable rubber ideal for casting moulds with complex geometry. Its translucency once cured makes it easy to locate parting lines and ensures the silicone has penetrated all hard-to-reach areas of the model.

Technical specifications

What it's used for

PlatSil 73-15 is a professional-grade casting silicone, particularly suited when a highly flexible, translucent, fine-detail mould is required. It can also be thickened with thixotropic agents such as PlatThix for brush application in blanket moulds. Its most common applications are:

• Casting moulds for reproductions in resin, plaster, wax or polyurethane.
• Moulds for parts with complex geometries, undercuts or fine textures where translucency helps detect bubbles or unfilled areas.
• Soft prosthetics for special effects and character make-up, including facial and body prosthetics.
• Moulds for Food Safe applications (FDA compatible), such as chocolate moulds, fondant moulds or artisan pastry.
• Casting moulds that will require cutting after demoulding, thanks to the visibility of the model through the rubber.
• Reproduction of artistic sculptures, collectible figures and special effects pieces.
• Manufacture of reborn dolls and hyperrealistic figures in combination with silicone pigments.
• Translucent silicone pieces tinted with specific pigments for platinum silicone.

How to use it

1. Prepare the model: ensure the surface is clean, dry and free of contaminants (sulphur, latex, tin, uncured epoxy). Apply a release agent if the model material requires it.
2. Weigh or measure the components: mix Part A and Part B in a 1:1 ratio by weight or volume. Use clean containers and spatulas, free of residues from other materials.
3. Mix: stir slowly for at least 2-3 minutes, scraping the sides and bottom of the container thoroughly, to achieve a homogeneous mixture without streaks. Avoid incorporating excessive air.
4. Degas (recommended): if you have a vacuum chamber, apply vacuum to the mixture for 1-2 minutes before casting to eliminate trapped bubbles.
5. Cast: pour the silicone in a thin stream from a low point of the mould box so the material rises gradually and displaces air. You have 20 minutes of working time.
6. Cure: allow to cure at room temperature (25 °C) for 4-5 hours without moving the mould. Curing can be slightly accelerated by raising the ambient temperature.
7. Demould: once cured, the silicone will not adhere to most materials. Demould carefully and remove the model.
8. Post-cure (optional): for demanding applications (food contact, prosthetics), a post-cure in an oven at 60-70 °C for 1-2 hours improves mechanical properties and eliminates any traces of free platinum.

Usage tips

Thixotroping for brush-on blanket moulds

PlatSil 73-15 has a viscosity of 2,500 cP, fluid enough for casting, but can be thickened by adding PlatThix (thixotropic agent for platinum silicones) in small proportions until achieving the consistency of thick paint or putty. This allows it to be applied in successive layers over vertical models without the silicone running, reducing the total material consumption compared to a solid block mould.

Tinting and prosthetic character work

The translucency of the cured rubber makes it an ideal base for hyperrealistic character work. Add specific pigments for platinum silicones directly to Part A before mixing with Part B. For special effects prosthetics requiring feathered edges on skin, combine it with an encapsulant such as Key-Cap Plastic to achieve imperceptible transitions during make-up application. If you need an even softer rubber for areas with greater movement, see the PlatSil Gel-00 range.

Temperature and cure time

The 4-5 hour cure time corresponds to 25 °C. At lower temperatures (cold workshops in winter) curing is considerably longer, potentially exceeding 8 hours at 15 °C. If you need to speed up the process, work in a heated environment or use a thermal blanket over the mould. Never use heat to compensate for inhibition: if the silicone does not cure under normal conditions, the problem is contamination and must be resolved by cleaning or sealing the model.

Frequently asked questions