Air that enters the mold making and casting materials can give rise to imperfections in the finished art piece. Vacuum degassing is the best method for removing the trapped air from flexible materials.
Mold making and casting involve a number of processes, basic among these is mixing the materials for making the mold or cast. Indeed, most mold making and casting materials like plaster, resins and rubbers need to be mixed either with water or the catalyst before use.
No matter how carefully the artist mixes the materials, some air is likely to enter the mixture. This shows up as air bubbles on the mold or cast which looks quite abhorrent and may even render the cast unusable.
Experienced artists try different tricks to eliminate the air bubbles – they mix the materials very slowly and pour it in a high, narrow stream from a corner of the mold/mold box. The latter will allow the trapped air to escape even while the material is being poured.
However, no method is foolproof. Some air still remains and can make the mold/cast look unsightly. The answer to perfect molds and casts is a vacuum pump with vacuum chamber.
What will the vacuum chamber do?
A vacuum chamber helps degas mold making and casting materials by removing all the air and other gases to create a vacuum. This is especially helpful for polyurethane and silicone rubbers apart from other slow-setting resins. This is because these materials cure to a flexible mold/cast which makes pressure pots quite ineffective in eliminating the air bubbles. The air will compress inside the pressure pot, but will spring back to its original size once it is exposed to the normal air pressure outside.
The shape and structure of the vacuum chamber matters here. Generally, box vacuum chambers are used for degassing while spherical and cylindrical ones are used for other types of testing. The materials used for the vacuum chamber also matter as some may allow atmospheric air leakage, thus playing havoc with the pressure inside the chamber. High density materials like brass, glass, acrylic, steel or aluminum are usually preferred for vacuum chambers. Even the thickness, resistivity and permeability has to be planned carefully. Then again, the other components like access ports, doors, hatches and sealing materials should be properly designed to ensure optimum usage.
The vacuum chamber requires a pump for lowering the pressure inside the container. It should create a vacuum of 29.9 inches of mercury (Hg) at sea level which is considered ideal for degassing. The pump used by auto mechanics to check the air-conditioning units in the vehicles will suffice here.
Else, artists can opt for the vacuum chamber and pump available at EnvironMolds. This features the appropriate shape, materials and structure that will be suitable for deairing rubbers, resins and other materials. The chamber even features optically clear acrylic plates for viewing the process while it is underway. The result will be smooth and perfect molds and casts sans any distortions from bubbles!