Making a Silicone Mold for a Concrete Planter
When making concrete castings, it’s important to choose a silicone suitable for use with concrete. This ensures that your mold will be as durable and long-lasting as possible.
Mold Star™ 15 Slow by Smooth-On is a two-component, platinum-cure silicone designed specifically for making precise and flexible molds. The silicone mold is easy to mix at a 1A:1B volume ratio and cures at room temperature without pressure or special equipment. The curing time is about 4 hours at room temperature.
Once cured, Mold Star™ 15 is flexible and captures fine details exceptionally well. It also has excellent tear strength. The silicone’s Shore A hardness is 15. It contains no harmful substances, is odorless, and is easy to handle. Mold Star™ 15 adheres well to many model surfaces without release agents, but for porous materials such as wood or plaster, a mold release is recommended.
A mold made with Mold Star™ 15 can be used for casting wax, soap, resins, plaster, or concrete, among other materials.
Mold Star™ 15 Slow is an excellent choice for both hobbyists and professionals who need a reliable, detail-reproducing silicone mold.
Step 1: Prepare the model and mold box
Attach your model piece to a baseboard using hot glue. Build a tight mold box around it and glue the frame to the base as well. Make sure everything is secure and that the mold box is completely sealed to prevent leaks.
Step 2: Measure and mix the silicone components
Measure equal parts of Mold Star™ 15 components A and B by volume. Pour them into a clean, dry mixing container. Mix thoroughly, scraping the sides and bottom, until the mixture is completely uniform.
Step 3: Pour the silicone into the mold
Slowly pour the mixture into one corner of the mold box so it flows evenly over the model and minimizes air bubbles. Ensure that the silicone layer extends at least 1.25 cm above the highest point of the model.
Step 4: Curing
Allow the silicone to cure at room temperature (around 23°C) for approximately 4 hours. Do not move the mold during this time.
Step 5: Demolding and finishing
Remove the mold box and carefully separate the cured silicone mold from the base and model. Your flexible, durable silicone mold is now ready for repeated use.
The video features the product Mold Star™ 16 Fast. In the Kevytrakentaja online store, you can find a similar product, Mold Star™ 15, which can be used for this same process.