Deairing With a Vacuum Chamber
Air bubbles tend to pop up in many a mold making and casting materials, especially polyurethane resins and silicone rubbers. It could be during the mixing stage or pouring stage, but the most diligent of artists still fall prey to the pesky boils that mar the appearance of the mold or cast. Some can even end up distorting the final cast in quite an unsightly manner.
Mold makers and casting artists try different tricks - from pouring the mold making material in a high and thin line to shaking the casting material vigorously so that the bubbles rise to the surface before popping them off with a pin.
Even a vibrating table or pressure pot is often used to get rid of the nasty air bubbles. But some irritating ones always tend to remain. So, nothing can do a complete job of eliminating the air bubbles like a vacuum chamber!
How does it work?
A vacuum chamber and pump work together to suck all the air out of the mold making and casting material. The deaired material will be entirely free of air bubbles and can be used safely.
All you have to do is properly mix the mold making or casting resin or rubber before placing it in the vacuum chamber. Keep in mind that the material will expand beyond proportion during the vacuuming process, so the chamber should be big enough to hold 4 times the amount of material that is being deaired!
Switch on the pump and let it work its magic. Once the chamber reaches 29 inches of mercury (at sea level), the material will begin to rise all around - like foam - for a minute or two. It will ultimately fall and plateau out showing that the air has been removed and there's no more air in the chamber. But it's better to continue to operate the pump and chamber for a few additional minutes.
Shut off the pump and open the release valve on the vacuum chamber to equalize the air pressure. Now the mold making or casting material can be removed and is ready for use.
While it will flow freely and smoothly, you still have to be careful when pouring the material as the process itself can again introduce annoying air bubbles into the mix. To counter this, some artists again place the entire mold box or mold into the vacuum chamber for a few minutes. This will not only remove any new air bubbles but also allow the material to settle into intricate and minute undercuts in the model or mold.
In sum, a compact vacuum chamber and pump makes the perfect addition to an artist's studio. It sits quietly in a corner and helps get bubble-free molds and casts quite effortlessly.
Go get yours right now!