As most of my readers would know, we use combinations of pressure and vacuum to remove bubbles from resin during the casting process. This is facilitated through the use of a pressure pot (this is a really old picture of mine):
Generally people use spray painting pressure pots converted to suit resin fasting duties, and in the US the cheapest options is usually the Harbor Freight item.
Over the past couple of years there have been a couple of instances of people having their pot fail. While the Harbor Freight pots are rated to 80PSI, we recommend running them at about 60PSI (this gives an adequate level of bubble removal), which should be well within any tolerances in the design. One RA member actually went through 3 of the Harbor Freight pots before he had an non-faulty one.
We have just had another RA member’s pot explode while he was standing over it (“explode” may sound a little more dramatic than it actually was) and while he was fortunately unharmed, I must stress that this can be potentially VERY dangerous. Many people don’t realise just how violent compressed air can be.
Because of this, we advise that people in the US do NOT purchase the Harbor Freight pressure pots to use for casting (or anything else for that matter). While it’s a lot more expensive, we highly recommend the C.A. Technologies 51-201C Resin (Mold) Casting Pot (http://www.finishsystems.com/resincastingpressurepots.html), which is a high quality unit and requires zero modification for casting.
Here in Australia we still recommend the 10L pressure pots sold by Super Cheap Auto (regularly on sale for $100), as per the picture of mine above. As yet I have not heard of any dangerous problems with these (I did have the thread on one of my clamping bolts strip so replaced them all with high tensile steel).
Remember that working with pressure and vacuum can be dangerous, so please everyone be safe! Never exceed the maximum pressure rating of the pot you are using.
If you have any concerns or questions please don’t hesitate to ask in the Resin Addict forum.