We are often asked if a vacuum chamber or a pressure pot is required in the fine fine art of mold making and casting. As with so many answers in life, a "yes" or "no" answer is not possible without first learning more information about the job. Except for water clear resin, where tiny air bubbles will obscure the clarity of a part, and such equipment is a must, my answer most often is, "It all depends. " That is ineffective, I understand. So the objective of this article is to provide the specific answer you are looking for.
For everyday mold making and casting, you can pour your materials in a high, narrow stream into one corner of your mold package to reduce the unavoidable air bubbles. This allows air to escape as it travels down the narrow stream when you are flowing. Vibrating the mold, or mold box helps, as well, either mechanically, by knocking on it with your knuckles, or by putting a vibration source against the mold container, such as a hand sander. These kinds of are all great studio tricks that will definitely reduce air bubbles. Nevertheless they do not eliminate them entirely. So if that is your goal, continue reading00.
So if you are planning to create conforms and castings on a regular basis then you should bite the topic and acquire the variety of of equipment to achieve professional results. Just as one can do cabinetry using manual operating tools like a hand saw, better and faster results are often obtained through the electric saw or chop saw. The right tools, for the right purpose, help in obtaining constant adequate results in any industry or hobby for that matter.
"What is the difference between the two and do I want both" are the essential that is questions I most often receive. As the names imply one chamber provides air pressure as the other removes air pressure. But only one actually eliminates air from your mildew making and casting materials - the vacuum chamber, while the other simply hides it--the pressure weed.
The pressure chamber works by providing up to 50-psi of atmospheric pressure. If you remember your high school science, normal sea level pressure is about 14. 7- psi. Therefore, the higher pressure works to compress any air pockets in your material and squeezes them down to almost microscopic size - thus making them appear to disappear. The air is still there though, but you just can't view the bubbles now. But, once you release the air pressure back to 14. 7-psi, the air bubbles will go back - that is unless of course the air is contained as it might be if the materials you were pressurizing solidified to a solid, like a hard resin, gypsum plast typer or epoxy. If your material was a mold rubber though, such as silicone or polyurethane, the flexible rubber will not contain the compressed air bubbles and they would expand within the rubberized normal again size, even though your rubber has cured.
Thus, the pressure container is best suited when your mold making or throwing material cures to a great and the vacuum holding chamber can be used to remove air from flexible rubbers. Typically the vacuum chamber can also de-air solid resins and epoxies, too. But since it takes a little more time to create a vacuum, and certain resins are fast-cured, the pressure chamber is the tool of choice in those instances as it can be quickly pressurized, faster than a vacuum holding chamber can be evacuated.