This usually occurs when too much rubber is applied at once. To achieve the best results when creating a brush-on mold, it’s essential to apply the rubber in thin layers, especially for the first layer.
Here are some helpful tips for successful application:
- Avoid Over-Applying: Applying too much rubber at once can cause it to sag or run off the model’s surface. Be mindful to avoid wasting rubber by applying it too thickly.
- Air Entrapment: Brush-on rubbers, like pourable versions, need to de-air. Over-application can trap air, leading to visible air bubbles in both the cured mold and any castings made from it.
- Proper Application: For the critical first layer, use a stiff paintbrush to apply a thin, even layer over the model’s surface. Begin at the top and work your way down, using a “stippling” technique to ensure the rubber gets into all the fine details.
- Mixing: Mix only a small amount of rubber at a time. If you mix more than you can apply within 15 minutes, the remaining rubber will likely become unusable. You can always mix additional batches as needed during the mold-making process.
- Colorant: Adding a small amount of colorant to every other layer will help you track your progress and ensure that each layer is fully covered.
By applying the rubber in thin, controlled layers and following these tips, you’ll be able to create a smooth, bubble-free mold. Remember, subsequent layers (2nd, 3rd, 4th, etc.) can be applied with slightly more material, but it’s important not to over-apply.