From Concept to Casting: Creating Your First Jesmonite Prototype

Design innovation doesn’t start in a factory… It starts on the workbench. Whether you’re a product designer, a maker, or a small-batch entrepreneur, Jesmonite gives you the tools to bring your boldest ideas to life with precision, performance, and a lower environmental footprint. But how do you go from a concept on paper to a prototype you can hold in your hands?

Here’s your step-by-step guide to creating your first Jesmonite prototype, from planning and pouring to perfecting and scaling up.

1. Planning Your Design: Sketch, CAD, or Sculpt

Every great prototype starts with a well-defined concept. That could be a hand-drawn sketch, a 3D CAD model, or even a sculpted maquette in clay or foam.

• Sketching helps you explore form, function, and proportions quickly.

• CAD modelling allows for precision, especially if you're planning to 3D print your master or replicate symmetrical components.

• Sculpting is ideal for organic shapes, decorative details, or when you need a tangible reference.

Before you move forward, ask yourself: does your design need flexibility, stone texture, or a metallic finish? This will inform your choice of Jesmonite product.

2. Choosing the Right Jesmonite Product

Jesmonite offers a family of high-performance materials, each tailored for different outcomes:

• AC100 – Perfect for decorative objects, tableware, tiles, and interior use. Lightweight, fast-setting, and easy to pigment.

• AC730 – Mineral-based with natural stone fillers. Ideal for achieving a stone-like finish and for exterior applications.

• Flex Metal – Real metal finishes in a pourable format. Create cold-cast bronze, copper, brass, or iron with over 70% metal content. (this is a finish used in conjunction with AC730)

Each system shares Jesmonite’s eco-conscious DNA, water-based, solvent-free, and safer to work with than traditional alternatives.

3. Creating a Master and Making Your Mould

Once your design is finalised, it’s time to make a master pattern (the positive). You can carve it by hand, 3D print it, or CNC-machine it depending on the level of detail required.

Then, you’ll create a silicone mould, the most popular moulding material for Jesmonite casting due to its flexibility and ability to capture fine details.

Pro tip: Make sure your master is properly sealed and mould release is applied to avoid tearing your mould or ruining detail in the first cast.

4. First Pour Tips: Ratios, Mixing, and Curing

Jesmonite is mixed by combining the liquid and base at a fixed ratio (varies by product, always follow the datasheet). Use a high-shear mixing drill and mixing blades for even dispersion and reduced air bubbles.

• Mixing time: Usually under 1 minute, don’t overmix or introduce air.

• Pour technique: Pour slowly from one corner to avoid trapping air.

• Vibration: Gently vibrate the mould to release any hidden air pockets.

• Curing: Leave to cure at room temperature. Demould times can be as fast as 30–60 minutes depending on the product and mould size.

Jesmonite cures fast but don’t rush the process. Let it reach full strength before sanding or finishing.

5. Troubleshooting Common First-Timer Issues

Even with a user-friendly system like Jesmonite, first pours can go sideways. Here are a few common issues:

• Surface bubbles? Try degassing or vibrating the mould.

• Streaky colours? Ensure pigments are fully dispersed before pouring.

• Weak edges or breaks? Thicker edges or glass fibre reinforcement can improve strength.

• Sticking to the mould? Apply more mould release or check for undercuts.

Don’t be disheartened, troubleshooting is part of the learning process, and every mistake teaches you something new.

6. Post-Processing and Surface Finishing

Now the fun begins. Jesmonite can be sanded, polished, sealed, or left raw depending on your design.

• Seal for protection: Use Jesmonite sealer for water and stain resistance.

• Sand to smooth: Start at 240 grit and move up for a honed or polished surface.

• Experiment with effects: Try metallic waxes, oxide washes, or surface polishing to bring out texture.

Remember, Jesmonite’s versatility doesn’t end when the piece comes out of the mould, there’s a whole world of post-casting creativity to explore.

7. Scaling Up for Small-Batch Production

Once your prototype is perfected, scaling up is straightforward:

• Use multi-cavity moulds for batch production.

• Invest in mixers and degas chambers if producing regularly.

• Switch to pigment-dosed kits or bespoke colour-matched batches to maintain consistency.

• Track ratios and curing conditions to ensure repeatable quality.

Jesmonite’s fast set times, low reject rates, and ability to capture fine details make it ideal for independent product lines, artist collections, or start-up-scale manufacturing.

Ready to Prototype with Purpose?

Jesmonite is a medium for turning ideas into tangible products. Whether you’re prototyping jewellery, homeware, lighting, or functional design, Jesmonite empowers you to build with confidence, experiment with style, and scale sustainably.

Want help choosing the right product? Get in touch with our team or request a sample kit to start experimenting.

The future of design starts with one pour. What will you cast?