We have all experienced those pesky little micro bubbles in our resin castings. In order to tackle the problem we first need to understand why they form.
The micro bubbles are simply trapped air that can not escape because of the viscosity of the resin.
Viscosity: "Viscosity describes a fluid's internal resistance to flow and may be thought of as a measure of fluid friction. Thus, water is "thin", having a low viscosity, while vegetable oil is "thick" having a high viscosity."
Because resin has higher viscosity/thicker than water, it traps air inside. The air enters the mixture when mixing your resin.
Tip 1: Before you start heat up your 2 part separately first. You can do this either by placing your bottles in the sun for a few minutes or by placing them in zip lock bags and in a lukewarm water bath. By heating the resin and hardener you lower the viscosity allowing more bubbles to escape the mixture
Tip 2: When mixing your resin, do it slowly and try not to add to much air. Mix for +/- 3 min and scrape the sides and bottom to ensure even mixing.
Tip 3: Once you have poured your resin into your mould, you can now tap the working surface or mould to help the bubbles rise to the top. When the bubbles are on the surface you can now pop them with your lighter or torch. (Be careful not to burn your mould as it will then stick to your resin.)
Tip 4: Baby sit your casting. What does that mean? You need to watch your work like you would a baby. From mixing your resin you have 20-40 min working time before it starts getting to thick to work with, in this time the resin can still release bubbles. Tap and torch your casting every 5 min during this time. If there are any trapper bubbles at the bottom you can also bring them to the top with a toothpick and pop them.
If you have tried the above 4 Tips and you are still not 100% happy you can try Tip 5.
Tip 5: Pressurize your casting. You can purchase a Pressure Pot from PoxyArt. This allows you to place your casting in the Pressure Pot whilst still wet. Pressurize your pot to 2.1Bar and leave it under pressure for at least 8 hours. The pressure compresses all the micro bubbles until they are no longer visible and gives you a crystal clear casting.
Remember the deeper your casting the more difficult it will become to remove the bubbles from the bottom, we then suggest using a Pressure Pot for best results.
