Silicone Addition Clear 25 Set – Glass-Clear Casting Silicone for Potting LEDs & Water Effects in Model Making

Premium Glass-Clear Casting Silicone for Professional Potting and Model-Making Applications

Silicone Addition Clear 25 is a pourable, addition-curing (platinum) two-component silicone that cures at room temperature to a glass-clear, flexible rubber with a medium hardness of Shore A 24 to 27. Once mixed, the material flows well (4,000 cSt at 23 °C) and is self-de-airing, linear shrinkage stays below 0.1 % and the refractive index is 1.406 at 25 °C. With a pot life of 130 minutes at 23 °C you have plenty of time for large or complex potting jobs; the product can be demoulded after 20 hours. The mix ratio is 1:1 by weight (100 parts A to 100 parts B); only combine components with the same lot number. Clear 25 is ideally suited to flexible potting of LEDs and optical elements and to recreating water and windows in model making.

Key Benefits

• Refractive index 1.406 at 25 °C: glass clear after curing – ideal where light and vision need to pass through the material, as with LEDs and optical elements.
• Hardness Shore A 24 to 27: medium hardness – flexible enough to protect components yet dimensionally stable.
• Linear shrinkage <0.1%: virtually shrink-free – dimensionally accurate potting without stress on components.
• Viscosity 4,000 cSt: very free-flowing and self-de-airing – little trapped air, even around fine components.
• Pot life 130 minutes at 23 °C: very generous working time – suitable for large pours and vacuum de-airing without time pressure.
• Mix ratio 1:1 by weight: easy to weigh out – can be mixed by hand or by machine.

Typical Applications

• Flexible potting of LEDs and LED strips
• Potting of electronics and optical elements
• Recreating water in aquarium scenes, dioramas and model making
• Windows and other transparent parts in model making, prop making and set building

Because of its low tensile strength (0.5 N/mm²), we do not recommend Clear 25 as a mould-making silicone. For clear moulds, Silicone Addition Clear 5 is a better choice.

Processing instructions:

1. Stir component A and component B separately and thoroughly before use.
2. Weigh A and B accurately in a 1:1 ratio by weight (100 parts A to 100 parts B). Only use components with the same lot number – mixing different lots can lead to curing problems.
3. Mix by hand or by machine, slowly and thoroughly in a figure-of-eight motion without folding in air, until completely homogeneous.
4. Preferably de-air the mixture in a vacuum chamber immediately after mixing to prevent trapped air.
5. Pour the mixture slowly from a single point within the pot life of 130 minutes (23 °C).
6. Only demould once fully cured, after approximately 20 hours at 23 °C. Curing in an oven speeds up the process, but air bubbles then have less time to escape. Pot life and demoulding time depend strongly on temperature: the warmer, the shorter both become.

Modifying, Colouring and Shelf Life

• Adding silicone oil lowers the hardness. Silicone oil does not cross-link and may migrate to the surface over time.
• To spread rather than pour, add Silicone Addition Thixo A or fumed silica. Do not use Thixo C, which is intended for condensation silicones.
• Colour with silicone pigment.
• At higher temperatures the material may develop a very faint yellowish haze; for most potting applications this is not a problem.
• The components are supplied as a set only and cannot be ordered separately. Larger pack sizes than those in the webshop are available on request.
• Stored in closed packaging in a cool, frost-free place, the product has a shelf life of at least 1 year.

Silicones and More, specialist in high-quality mould-making rubbers and casting materials for professional makers.

Important Warning: Inhibition of Addition Silicones

Please note: This is an addition silicone (platinum cure). Curing can be inhibited by sulphur, nitrogen, amine compounds and metal salts. If you are unsure whether the materials you use (gloves, spatulas, cups, models) contain these substances, carry out a small test first. Inhibiting substances are found in, among other things, latex gloves, some plasticines, paints and adhesives, condensation silicones, one-component silicone sealant, natural rubber and 3D printing materials (especially stereolithography). If in doubt, apply a separating layer of polyvinyl alcohol (PVA).

Professional Support

Silicone Addition Clear 25 is our glass-clear choice for flexible potting with a long working time. If you are looking for a softer clear silicone, take a look at Silicone Addition Clear 5 or Silicone Addition Clear 0. If you are unsure which best suits your application, contact us at info@siliconesandmore.com; we are happy to advise you.