So you have purchased your first Jesmonite AC100 Kit and are super keen to show off your first few projects but notice a couple of small pin holes in the surface of your work! Here is a short guide explaining some of the technique to minimise or eliminate those pesky air bubbles.
Slowly Add Powder to Liquid:
When mixing always add the Jesmonite powder to the liquid component gradually, not the other way around. This helps prevent air from getting trapped within the mix. A well mixed Jesmonite Powder and Liquid will appear smooth and silky with not flaws or uneven bumps throughout the body of the mixture.
Mix Slowly and Gently:
Mix the components slowly and gently to avoid introducing air into the mixture in you are mixing by hand. Stir carefully and avoid rapid or vigorous movements.
Pour Slowly into your Mould
Slowly pouring your Jesmonite into your mould from a height of about 10cm will also help release air from your mixture. The smaller stream while pouring will facilitate this will good end results.
Brush On Method
If your project and mould allow it, you can brush a layer of your mix Jesmonite onto the surface of your silicone mould using a paint brush. Employ a technique which delivers an even coverage on the bottom and sides of the project prior to your main pour. This can make a difference and eliminate air bubbles on the surface of your finished project.
Use the Jesmonite High Shear Paddle Mixer:
Using a Jesmonite paddle mixer with a low-speed setting really does help you achieve a consistent and bubble-free mix and is arguably the most effective method to avoid air bubbles. Keep the paddle submerged in the mixture and mix slowly. I know its an extra expense to consider but Jesmonite recommend using one every time you mix your Jesmonite for the very best results.
Scraping and Folding:
During the mixing process always scrape the sides and bottom of the mixing container to ensure all the material is mixed evenly. You can gently fold the mixture from the sides back into the body of your mix to release any trapped air.
Deaeration:
You can use a vacuum chamber or a vacuum pump with a degassing chamber to remove air bubbles from the Jesmonite mix. Place the mixed Jesmonite into the chamber and apply a vacuum to draw out the air bubbles. This is a very effective method in an ideal world but may not be accessible or affodable for everyone.
Tap and Tickle!
After pouring the Jesmonite mix into your mold, gently tap the mold on a flat surface to help release any additional air bubbles. This can be particularly useful for larger molds. Experienced Jesmonite Crafters will also raise the poured mould a few centimetres from the work surface before dropping the project back down. This is effective in moving and releasing more stubborn air bubbles.
Allow Settling Time:
Sometimes, allowing the mixed Jesmonite to sit for a few minutes before pouring it into the mold can help air bubbles rise to the surface and escape. Very gently tapping the mixture on your work surface can help release trapped air.
Work in Controlled Conditions:
Temperature and humidity can affect the curing and setting process. Working in a controlled environment will minimise the variables that could contribute to air bubble formation and give consistent results every time.
Remember that the specific technique your employ may vary based on the shape and size of your project, so you may need to experiment to find the best methods for your particular application. Additionally, always follow the manufacturer's guidelines and recommendations when working with Jesmonite AC100. If you have any questions please get in contact with us as we would be happy to help work through any issues you have when working with Jesmonite.