Beyond Silicone: Casting Jesmonite® in Different Materials
When working with Jesmonite®, your mold choice can make or break your final piece. The good news? Jesmonite® is incredibly versatile and forgiving to work with. And it’s important to note some materials will give you better results (and a smoother experience) than others.
Let’s walk through your options, starting with the most creator-friendly choice.
Silicone Molds: The Gold Standard
If you’re looking for the easiest, most reliable way to cast Jesmonite®, silicone is hands-down the best option.
Silicone molds are flexible, non-stick, and highly durable which makes demolding quick and stress-free. They also capture fine detail beautifully, which is where Jesmonite® really shines.
Why creators love silicone molds:
- Easy demolding (no cracking or sticking)
- Reusable for multiple casts
- Captures intricate textures and details
- Minimal prep required
Because Jesmonite® picks up every detail, silicone ensures you get a clean, professional finish right out of the mold.
Tools That Make Silicone Even Better
Pairing silicone molds with the right tools makes your process even smoother.
Silicone Mixing Cups
Silicone mixing cups are a must-have for Jesmonite® projects if you’re making regularly. They’re flexible, reusable, and perfect for reducing waste.
One of our favorite techniques? Make terrazzo chips right in your mixing cups.
Instead of throwing away leftover Jesmonite®, use a spatula to spread your excess Jesmonite® around the edges of your mixing cup. Let it cure in the cup, then peel it out and break it into chips for future terrazzo designs. We like to toss our chips in a mason jar and let our collection build over time! It’s an easy way to have nearly zero-waste and makes for adorable terrazzo projects in the future. Watch our tutorial here.
Shop our silicone mixing cups.
P.S. We've tried dozens of mixing cups in our years of making and finally found the perfect cup for mixing and making terrazzo. These cups were selected by Jesmonite® lovers FOR Jesmonite® lovers!
Silicone Spatulas
A good silicone spatula helps you scrape every last bit of material into your project. It minimizes waste and gives you better control when mixing pigments and pouring. It also makes clean up a breeze. Simply knock off extra Jesmonite® mix into your two-bucket system immediately after pouring or let it dry on the spatula and it will easily crack and peel off. From there you can rinse with warm water and you’re ready for your next creation.
Casting Beyond Silicone: DIY & Alternative Molds
While silicone is the easiest option, it’s not your only option.
Jesmonite® is historically a building material and can be cast into a wide variety of materials, which opens the door to custom shapes and larger-scale projects.
Building Your Own Molds
You can create molds or casting forms using materials like:
- MDF (medium-density fiberboard)
- Melamine boards
- Acrylic sheets
- Plastic containers or packaging
These are especially useful for geometric shapes, trays, panels, or architectural applications.
Important Tips for Non-Silicone Molds
When working with alternative materials, there are a few key things to keep in mind.
Use a Mold Release
Unlike silicone, most rigid materials will not release Jesmonite® easily on their own. We recommend using a mold release wax or agent to:
- Prevent sticking
- Protect your mold surface
- Ensure a clean release
Skipping this step can result in damaged molds or worse, damaged pieces.
Be Mindful of Surface Detail
Jesmonite® is known for its ability to capture incredibly fine detail. That means whatever texture is inside your mold will show up in your final piece.
Smooth surfaces = clean, polished finish
Textured or rough surfaces = visible imperfections
If you’re building molds from MDF or other porous materials, you may want to seal or sand them beforehand for a smoother result.
You Can Always Refine the Finish
If your cast picks up unwanted texture, don’t panic. Jesmonite® can be sanded after curing to refine the surface. Start with a coarser grit and work your way up for a smoother finish.
Real Project Example: Casting Flagstones with Jesmonite® AC730 Micro-Concrete
To demonstrate more advanced casting, here’s an example of how we cast flagstone-style pieces using plastic molds and Jesmonite® AC730 micro-concrete.
Step 1: Prep Your Mold
Start by making sure your plastic mold is clean and completely dry. Then, using a clean cloth, apply a thin, even layer of mold release wax throughout the mold. Ensure you reach all corners and surfaces of the casting area.
This step is critical. It ensures your piece will demold cleanly once cured and helps preserve the life of your mold.
Step 2: Apply a Gel Coat
Because these are larger, more structural casts, we begin with a gel coat layer.
Pour or brush a thin layer of Jesmonite® into the waxed mold first. This captures all the surface detail and creates a clean outer finish.
Step 3: Reinforce with Glass Fibers (optional)
Next, we mix in chopped glass strands and add this reinforced Jesmonite® into the mold.
This step adds structural strength, which is especially important for larger pieces like garden stones that need durability.
Step 4: Backfill the Mold
Once reinforced, continue filling the mold until full. Make sure to work the material into all areas to avoid air pockets and ensure consistent coverage.
Step 5: Demold and Finish
After curing, the piece can be removed from the mold. Because of the wax and gel coat, you’ll get strong detail reproduction, even with textured surfaces like stone.
If needed, lightly sand any areas to refine the finish.
This process highlights just how well Jesmonite® captures texture. Every crease and surface detail from the mold transfers into the final piece, which is exactly what makes it ideal for realistic stone effects.
Final Thoughts
If you’re just getting started, silicone molds are the easiest and most reliable way to work with Jesmonite®. They simplify the process and help you get beautiful results right away.
As you gain confidence, experimenting with DIY molds and alternative materials can unlock new creative possibilities from custom shapes to large-scale designs.
No matter what you choose, the key is understanding how Jesmonite® interacts with your mold because the better your mold, the better your final piece.
Follow us on Instagram @ftc.creative and on Youtube @ftccreative for more tips, tutorials, and creative inspiration using Jesmonite®.
