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There is very useful information on-line about converting 2-1/2 gallon paint pressure pots on-line. One you-tube video shows this in great detail, while a .PDF shows combining pressure and vacuum into one pot, requiring two gauges and a vacuum pump. I like to find the cheapest, simplest way to do the job, so without further ado, here is my poor(er) man's option. I began with scrounging up an old mechanic's or HVAC hand pressure gauge set. Since most of the modern world has gone to expensive, fancy machines to cature freon, these gauge sets are readily available. They are distinguished by having a low-side gauge, which reads both vacuum and pressure (up to 12o PSI), and a high-side gauge, which reads pressure only, usually up to 300PSI. They may be configured for either R-12 freon, R-134a freon, or whatever is current in the HVAC field. Doesn't matter which you use, as all you will need are the low-side gauge, the hose, and the appropriate fitting for the vacuum pump end of the hose. I had an old set laying about that was already broken. The high-side gauge had been broken off, but the rest was intact. After removing the hose, and the low-side gauge, it looked like this: The low-side gauge looks like the next photo where the "P" and "V" refer to the pressure and vacuum reading parts, respectively. The next thing required is a vacuum pump. Usually, the recommendation is either a purpose-designed pump or a recycled refrigerator pump. Since I also had a cheapie (read about $29.00) automotive venturi-type pump, I used that. The photo below shows mine, where the hose from an air compressor comes in (about 100 PSI needed), and shows the odd-ball adapter I added, so I could use the pump with either R-12 or the later R-134a type car setups. If you use one of these, it doesn't matter, as long as you can adapt your hose from the pressure pot to the pump. The fellow on-line that offers the PDF file gutted his pump, and just hooked up the guts. That was a little to exposed to damage for me, plus I already had the hose and fittings, so I went that route. I suggest you due a search on-line and then go your own way. The next photo shows my hook-up to the pressure-pot's lid: The next photo shows some of the mods to the pressure pots, that are pretty much the same for everybody, given I only use one gauge. Of note are the 1/4 turn air shut-off valves, red for the vacuum side and yellow for the air pressure side. These coors are not significant, and only ended up because I got the valves at two different places, and one had a female end where the other had a male end, and they ended up in these positions solely because of the brass fitting I had laying around. I did have to buy a couple, and they are available at automotive stores or big-box or hardware stores. Also shown below is the T-handle for the pressure regulator. The pot supports 60 PSI. I set the regulator shown here at 50 (AFTER setting the pressure relief valve, shown later to 55 PSI). Below is another view of the pressure pot lid: All joints are sealed with three wraps of teflon tape. The "T" fitting under the regulator was actually supplied on the pot as a piece of cast pot metal or some-such, and it gave me fits trying to get it to stop leaking. I finally replaced it with a brass fitting. A WORD OF CAUTION HERE!: Before doing ANY mods to your pressure pot (should you try one!), Follow the instructions, put it together and then pressure test it up to 60 PSI and see whether it will hold the pressure for an hour or so. Get yourself a real bottle of leak detector fluid from your plumbing supply stockist. Do not rely on the dish soap and water mix, as it is NOT sensitive enough. The right stuff will show you tiny leaks, by exhibiting dozens of really tiny bubbles, a half-hour after you apply it, if any leaks exist. Regular soap mix will fool you into thinking you are leak-proof, even if you aren't. You may feel free to ask how I know this... In any event, if you cannot seal the factory-provided parts prior to your modifying the pot, take it back, and exchange it for another! I got my pot off E-bay for $33.00 plus shipping, when the pot usually goes for around $100.00 new from Harbor Freight, so I figured that there would be some problems. I had to replace some fittings, chase the threads in the lid itself, and replace the original lid gasket, so I ended up being in it for around $80.00 all up. If you sign up on the Harbor Freight website, they will eventually send you a coupon worth $20.00 off a $100.00 purchase. Since they also sell the quarter-turn valves cheaply, pop for a couple and -- Bob is somehow related again. The fellow who has the you-tube video suggests cutting a wooden disc out of 3/4" ply to make up for the fact that the bottom of the pressure pot is NOT flat. Below, is my quickie answer, a piece of 3/4" lumber cut to length. I will probably do a proper circle covered with some resin-shedding product eventually. I also added a plastic 4 or 5 quart plastic ice-cream container to catch resin burps, etc. Below is a look at the whole shebang, put together. BTW, tighten the lid clamps as tight as you possibly can! Below is a picture of the compressor I use to drive this pot. It is kept in my garage, and normally used for putting air into tires or driving nails or other housely things. It replaced a larger, old one I had for driving air tools and such years back, that finally gave up the ghost. Also, please be aware that your airbrush compressor will not drive this rig, unless it's pretty awesome. I set the regulator on the output end of this compressor to 60 PSI, when used for casting. I usually use this rig as follows: I make the mold masters in one of the time-honored traditional ways, the I mix the RTV rubber in a larger cup than needed. I put the rather violently-stirred mix into the pot, shut off the pressure intake side, and then plug the compressor onto the venturi vacuum pump. I can pull between 24-26 inches of mercury with this setup (anything over 20 is fine). When the vac hits 20+, I shut off the vac side also and turn off the venturi pump. I give it 2-3 minutes under vacuum, then pull the relief plug to release the vacuum (semi-slowly). When the gauge reads zero, I open the pot and pour the degassed mixed silicone into the molds. I then put the molds into the pots. Unless they are somewhat large, I do not use vacuum at this stage, but if the molds are larger or have adequate pour stubs to contain the resin, I might use vac before pressure (perhaps 2 minutes). For the rockets and gun barrels, I used none -- just pressure. If I have used pressure, I simply shut off the vacuum side while holding the vacuum, re-attach the air hose to the pressure side of the pot, and start up the pressure -- again, without releasing the vacuum, if used. I then wait until the pressure pot hits 50 PSI, and then walk away for the needed time for the resin to cure, Then, I'll return, shut off the pressure side, and pull the relief valve to De-pressurize the pot and remove the castings. The air compressor will turn on and run if needed due to tiny air loss, to maintain the needed pressure. The last photo shows some of other folk's resin masters that I test the rig with. There are 1/72 rockets and machine gun barrels, and a Hasegawa B-26C turret sprue. The 20mm tailgun turret in the center is my master. I have cast resin in various ways for many years, and this is the first time I have ever gotten perfect casts, all the time. Any minor problems I have had are all resulting from improper mold design. One last thing I neglected to mention. I so far have used OOMOO 30 silicone and Micro Mark's CR-900 resin, mostly because of longer pot times (15-30 minutes). This gives me time to do all the de-gassing, but are not suitable for production work. The CR-900 however, has one very useful feature -- that tiny molding, like the rockets and gun barrels become very hard and strong AFTER SEVERAL DAYS. This stuff is great for super thin castings, but you could probably do better for thicker stuff. Thanks for tuning in. Comments, suggestions or outright attacks always welcome. Ed