Ever tried to pour silicone and ended up with a sticky mess? Or wondered why one mould lasts years and another cracks after a week?

If you’re looking for the best silicone for mould making UK-wide, you’re in the right place. Whether you’re casting resin, wax, or even prosthetics, the type of mould making silicone you use can make or break your results. In this article, we will walk you through the differences between condensation and addition cure silicones, how shore hardness matters, what causes inhibition, and what to look for when buying.

Key Points:

Why Use Silicone for Mould Making?

If you’re looking for the best silicone for mould making UK suppliers offer, it helps to first understand why silicone is such a popular choice. 

Whether you’re casting resin figures, wax models, scar wax, soaps, or SFX makeup prosthetics, silicone gives you reliable results with impressive detail. It’s also much more forgiving to work with compared to other materials.

For more on adhesives used in SFX work alongside silicone moulds, read up on what is spirit gum.

Flexibility

One of the biggest benefits of mould making silicone is how flexible it is. Unlike rigid plastic moulds, silicone bends and stretches, making it easier to remove your final cast without damaging it. This makes it ideal for capturing intricate details or working with undercuts.

Temperature Resistance

Silicone handles a wide range of temperatures, from freezing cold to baking heat (up to 400°C). That means you can pour in hot wax or resin without worrying about warping or melting the mould. Once cured, your mould is ready for anything—freezing, heating, or stretching.

Reusability

The best silicone for mould making isn’t just flexible—it’s also long-lasting. You can reuse it many times without losing accuracy, especially if you follow simple care tips. Clean the mould gently, avoid stacking during storage, and make sure it’s completely dry between uses.

Limitations to Know

Like any material, silicone has its downsides. It’s more expensive than liquid latex or rubber, and if stretched too far, it can tear. Not all silicone products are the same either—some cheaper options may not cure properly or may degrade quickly over time.

Tip: When buying silicone for mould making, always choose a trusted brand with good user reviews. Low-cost options may seem appealing but can lead to failed casts and wasted materials.

Types of Silicone for Mould Making

When looking for the best silicone for mould making UK makers rely on, understanding the different types available is a solid starting point. 

The two most commonly used are tin cure (also called condensation cure) and platinum cure (also called addition cure). Each has specific benefits, depending on the project.

Tin vs Platinum: What’s the Difference?

Both tin and platinum silicones are RTV (room temperature vulcanising), which means they cure without added heat. The difference lies in the catalyst used:

• Tin silicone uses tin salts to start the curing process
• Platinum silicone uses platinum as the catalyst

This small change makes a big impact on working time, flexibility, cost, and durability.

Tin Cure (Condensation Cure) Silicone

Tin cure is one of the most accessible types of silicone for mould making, especially for large-scale or one-off projects. It’s cheaper, easier to mix, and typically has a longer pot life (more time to work before it begins curing).

Key Features:

• Often used for industrial moulds, props, candle waxes, and general casting
• Compatible with resin, plaster, and wax
• Resistant to inhibition — cures well on almost any surface
• Typically mixed at a 10:1 ratio (base to catalyst)
• Not skin-safe and not suitable for life casting

However, tin silicone has a shorter shelf life. A mould making silicone made with a tin base may only last 12 months before it begins to tear or leach. It’s ideal for short-term or high-volume use, but not for making long-lasting moulds.

Platinum Cure (Addition Cure) Silicone

If you’re casting prosthetics, life-casting, or making detailed reusable moulds, platinum cure silicone is usually the best silicone for mould making. It offers greater tear strength, longer mould life, and higher detail capture.

Key Features:

• High tear strength and reusability
• Very low shrinkage
• Skin-safe (ideal for special effects and prosthetics)
• Can be mixed with additives like thinners, thickeners, or pigments
• Shorter working time, may require a retarder for complex pours

However, platinum silicones are more sensitive to inhibition. If your master or tools contain sulphur (like some clays or latex gloves), curing can fail entirely.

Tip: Silicone sticks to silicone—always use a release agent when pouring one into another, and avoid cross-contamination between tin and platinum cure systems.

Addition Cure Silicones

When choosing the best silicone for mould making UK artists can trust for professional work, addition cure (platinum cure) silicones often come out on top. These are the go-to choice for lifecasting, prosthetic applications, and any project where detail and durability matter.

Why Use Addition Cure Silicone?

Addition cure silicones are incredibly versatile. They’re skin-safe, have virtually no shrinkage, and can be used to cast everything from fine art pieces to wearable SFX prosthetics. If you’re working in makeup, props, or model-making, these silicones give you the accuracy and finish you need.

What makes them even more flexible (no pun intended) is the wide range of additives available. Depending on the job, you can tweak the mix with:

• Thickeners for vertical application
• Thinners for better flow into fine detail
• Retarders to slow down curing if you need more working time
• Accelerators to speed up the process for quick moulds
• Pigments to colour your silicone for visible prosthetics or finished castings

This customisation is one of the reasons why platinum silicone is often seen as the best silicone for mold making, especially for professionals.

Avoiding Inhibition

One thing to watch out for with platinum cure silicones is inhibition—when the silicone refuses to cure. This is usually caused by contaminants like:

• Sulphur (found in some clays)
• Latex (found in gloves and mask materials)
• Residue from tin-cure silicones

To avoid inhibition, use sulphur-free clay and nitrile or vinyl gloves. Keep your working environment clean and separate materials that could interfere with curing.

Tip: Always check that your gloves, tools, and master are free of latex and sulphur before pouring a platinum silicone. Even a small amount can stop it from curing properly.

Working Time and Cure Time

One of the key differences between platinum and tin cure silicones is how fast they set. Platinum silicones often have shorter working times. This can be helpful for quick casts, but if you’re working with a larger or more detailed mould, it might be too fast.

You can slow the process down using a retarder or by chilling your materials slightly. This gives you more time to mix, de-gas, and pour.

Making Your First Silicone Mould

To get started, you’ll need a few basic supplies:

• A master (the object you’re casting)
• Liquid mould making silicone
• A mould housing box (can be acrylic, plastic, or cardboard lined with tape)
• A release agent (optional, but useful for tricky shapes)
• Material to cast into the mould (e.g. resin, wax, or soap)

One-Piece vs Two-Piece Moulds

Before pouring, decide whether your mould will be one-piece or two-piece.

One-piece moulds work well for simple shapes with one flat side. They’re quick to make and easy to use.

Two-piece moulds are better for complex shapes with undercuts or full 3D detail. These take more time to set up but give you better flexibility for detailed casting.

If you’re unsure, start with a one-piece mould to practise mixing and pouring.

Pros and Cons of Cured Silicone

	Addition Cure Silicone	Condensation Cure Silicone
Price	Higher	Lower
Skin-Safe	Yes	No
Detail	Excellent	Good
Working Time	Shorter (can be extended with additives)	Longer
Durability	Very high – lasting for years	Moderate – Lasts months at a time
Inhibition	Can be affected by sulphur, latex, or residues	Cures well on most surfaces

Use SFX Tools By Treasure House of Makeup for Moulding and Prosthetics

Whether you’re sculpting prosthetics or experimenting with mould making silicone, we stock reliable products used by SFX artists, theatre professionals, and makeup students across the UK. 

For flexible casting, sculpt gel is an ideal choice for skin-like effects, while Mehron Scar Wax is perfect for quick mould-free texture work. Looking to avoid latex in your practice? Check our makeup blog for ideas regarding liquid latex alternatives for safe, effective substitutes.

Be sure to explore these other creative uses for silicone moulds outside of stage makeup.

FAQs

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Why has my silicone mould turned out sticky or soft after curing?

This is usually due to inhibition, poor mixing, incorrect ratios, or contaminants (e.g. sulphur, latex, or moisture). Re-check your materials and environment. If unsure, run a small test cure before committing to a full mould.

Can I apply a release agent to help remove silicone moulds?

Yes. While many materials don’t stick to silicone, using a universal mould release (especially on complex or porous masters) helps prolong mould life and ensures clean demolding—especially if you're casting resins or other silicones.

Sources

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Brewer, S., (2022) 15 Creative and Educational Uses For Silicone Molds. Steam Powered Family. [online] Available at: https://www.steampoweredfamily.com/15-creative-and-educational-uses-for-silicone-molds/ [accessed 08/08/2025]