Which vacuum pot to buy?

[David Wittner]

I inadvertently hooked a friend on turning, well maybe not so inadvertently. Anyway, he wants to get into resin turning--casting bits of god-knows-what in epoxy and turning them into bowls and hollow forms. His wife wants to get him a vacuum pot and pump as a present and asked me which one she should get because all of this is my fault anyway. Other than googling, this is out of my wheelhouse as I don't turn plastic. I figured that his max turning capacity is 15". Thinking he probably won't max out his lathe, therefore go with a pot that can hold something 12" diameter or so plus an inch or two of space around whatever it is he's casting in order to get the thing in and out. Basically that comes down to a pot that's around 15" in diameter. Is my thinking about this all wrong? I don't know exactly what he plans to cast and turn but can guess from the videos he shares, basically bowls and hollow forms.

If anyone has experience with this or suggestions, I'd appreciate it. Told his wife I'd ask the experts.

Thank you and turn on!
,
DGW

 

[Bill Blasic]

This is a very good one - California Air Tools 365CR 5-Gallon Pressure Pot for Casting - Rockler $250 It is the one I use and the best per price available.

 

[David Wittner]

Thanks Bill, so is pressure preferable to vacuum? I'm guessing this is another can of worms...

 

[Richard Coers]

You have a minimum of a week of research ahead of you to understand techniques, but most use a pot for vacuum to stabilize wood, and pressure to reduce the bubble size for casting.

 

[Tom Lucas]

For epoxy, a pressure pot is the best tool. You use it with a compressor. Vacuum pots are best for removing air so that stabilizer can fill in its place (stabilizing). Here you need a vacuum pump. Two different setups for two different purposes that are not really interchangeable.

 

[Dave Hulett]

For casting it's a preassure pot. Harbor Freights peassure pot fof $110 is hard to beat and if you have a 20% off coupon (not hard to find) it's a steal. I reworked the plumbing with a new gauge and valve. there are lots of youtube videos on setting one up, but like Zach Higgens youtube channel ...search for pressure pot

 

[Rusty Nesmith]

If you are only going to cast resin a pressure pot would be better. It is a lot less messy. The only thing I would use a vacuum pot for is to stabilize wood and I can make my pressure pot do that also if I needed to.

 

[Karl Loeblein]

If you are only going to cast resin a pressure pot would be better. It is a lot less messy. The only thing I would use a vacuum pot for is to stabilize wood and I can make my pressure pot do that also if I needed to.

Rusty, What pressure pot do you have?

 

[Rusty Nesmith]

Rusty, What pressure pot do you have?

I bought the big one from Harbor Freight and converted it to what I wanted. I didn’t have to add much.

 

[Erik Christensen]

If you want void free resin castings you really want both vacuum and pressure.. You don't need a second pot, as a pressure pot is more than strong enough to withstand any vacuum you can put on it - you just need a second top setup for your vacuum system. I made mine from two layers of 3/4 BB ply with a 1" plexiglass viewing port - you need to be able to see what is happening in the pot as you pull a vacuum as things can bubble over if you have a lot of entrained air in your project. The nice thing is you really don't have to worry about clamping your homemade top to the pot as air pressure does that for you as you apply vacuum - I just put a thin sheet of foam on the underside of the top and ambient air pressure does the rest - here is my top on the pressure pot -

had to seal the edges of the plywood with resin as it pulled air through the interior of the ply when it got to about 15" of vacuum. Vacuum pump from parts @ https://www.veneersupplies.com/categories/Vacuum__Press__Items/Vacuum__Press__Kits/.

To get a void free cast - fill your mold with resin (with some headroom for bubbles), put under vacuum, after a minute or so when bubbling slows down shut of vacuum pump, top off resin in mold and back into vacuum chamber. I use a slow set resin with about a 50 min pot life @ 70 degrees - so 10 min to mix & fill mold, another 10-15 min to cycle vacuum 2 or 3 times, then pressure top goes on and I have another 30 min or more under pressure to have the resin fill 100% of the now air free voids. I often use scrap ply discs as a waste block and this process will force with resin into the interior voids of plywood!!

You can always fill voids with thickened colored resin after you turn to final shape, but that adds a day or so the the production time - it is much easier to take a few minutes on the front end to eliminate voids in your resin casts.

My 2 cents....

 

[Bill Blasic]

Are voids a real thing? I've never run across a void with pressure casting. As always you learn something new every day.

 

[Erik Christensen]

Bill -
depends on what you cast - here in the desert there are not a lot of choices as far wood goes, so you can't be too picky - voids, bug holes, etc that would have you consider a piece firewood is just something I have to learn to work with as it is all I have. I did a resin bowl blank with pine cones once and learned that a pressure pot will only eliminate bubbles below a certain size, it will make a large bubble smaller but they are still there when you take it out of the mold.

I have never had a void after cycling under vacuum a couple of times - as an experiment I had a blank out of the mold when I decided I wanted to add more resin to get the rim up to where I wanted it, so before I put it back in the mold I drilled a bunch of holes in it, including in the bottom, and did the second pour out of a contrasting color for the rim and accent holes. When cured there were zero bubbles even in the large holes in the bottom - I doubt that would have been possible with just pressure. Not sure it is necessary in every instance, but I have the equipment, it does not take that much time and I get flawless results so that is what I do. Each to his own.

 

[Bill Blasic]

Erik I do not doubt what you say it's just that I have never ran into a void casting and that includes a very big pine cone. Maybe the orientation of the holes in the casting could make a difference. If the holes face downward the pour would have trouble pushing air out where if the holes are facing up the pour has no problem pushing air out as it flows in.

 

[Bob Brown]

It depends on what product you're using. Sometimes resin and epoxy are used as one and the same. For example Alumilite is urethane, requires extremely dry wood and pressure pot to reduce air bubbles. Easy to turn. West system is polyester, wood fairly dry, pot can be used but not always necessary. Robert Chatelain, one for the best at using wood and resin uses a completely different epoxy and gets great results. Marilyn Campbell uses west system, you can add a product referred to as balloons. Those are used to thicken the epoxy as thick as peanut butter. The alumilite product called deep pour also does it need a pressure pot. Top boat has several different epoxy/resin options. As for the pot, the California one is a good value. I suggest that you look at Robert Chatelain s work, he's retired and his original page is taken down. And also look at marilyn Campbell s work.

 

[Joe Div]

so many opinions/advice and examples! I'm confused/flabbergasted as to what to do. I simply want to create something to turn on my wood lathe, make a form ( using maybe an empty marshmallow container or equivalent ),put some pine cones or wood sticks, crayons, chunks of wood etc and then fill with resin. I've seen some beautiful items/vases/bowls made like this on utube. I'm thinking I need BOTH a vacuum AND a pressure pot. With these thoughts in mind what does anyone suggest??

 

[Joe Div]

well, I just bought a 3gal vacuum pot off of FB market place for $40 + shipping, seemed like too good a deal to pass up. NOW maybe I'll also but a 3-5 gal pressure pot, this way I'll have all bases covered. All I need now is pressurepot recommendations and what resin to buy/use. Thanks to all in advance for helping me with this journey so as to make the learing process less expensive and filled with errors/mistakes.

 

[DON FRANK]

A better solution for what Erik suggested is to vacuum the resin in a mixing container and be sure the resin only fills the cup 2/3 of the way up the cup. It will bubble and loaf up and if the resin is too high in the cup it bubbles over and makes a mess. After vacuuming then pour the resin into your container with the wood and then pressure pot. This two step process is unnecessary for most applications and only works if your resin has a long "open" pot life like 10-20 min. You need to have as much time as possible to do both processes like Erik described. If you are doing blended resin with multiple colors you simply mix up each container (separate color) in individual containers, vacuum them all at once then pour them into the wood mold. If you pour a little of one, then then some of the second, and third and go back to the first you will get a really nice swirling of the blended colors in the finished piece.

Vacuuming removes all the tiny bubbles that were caused when you thoroughly mixed the products.

Pressure potting greatly reduces the size of the bubbles to a size that they are not visible it doesn't remove them. It also strengthens the resin because it removes the honeycomb make up caused by trapped air bubbles. Pressure casting with wood also drives the resin deep into the pores and open cavities of the wood. The longer you can pressure pot before the resin begins to cure the better. That is why a resin that has a 10-20min pot life is much better than one with a 3-5min. Also the longer the pot life the less heat that is created during the curing process which is very important.

In general, pressure potting alone is plenty good for our purposes. I poured plastics for a living and had multiple pressure pots, the largest was bigger than a 55 gal drum so we could do lots of product at once. There were times when we vacuumed and pressure potted but most of the time pressure potting alone is good enough. VERY IMPORTANT, DON'T RUN THE PRESSURE HIGHER THAN 65-70LBS. It gets very dangerous and you cannot see the difference in results by going with higher pressure. Search you tube for pressure pot failures and it will sober you.

If you feel the need to vacuum you can pick up an old pressure pot used for canning and put on the plumbing to make it into a vacuum pot. Or you can get a thick piece of lexan for the lid if you feel the need to see what's going on.

 

[Darryl Fective]

It depends on what product you're using. Sometimes resin and epoxy are used as one and the same. For example Alumilite is urethane, requires extremely dry wood and pressure pot to reduce air bubbles. Easy to turn. West system is polyester, wood fairly dry, pot can be used but not always necessary. Robert Chatelain, one for the best at using wood and resin uses a completely different epoxy and gets great results. Marilyn Campbell uses west system, you can add a product referred to as balloons. Those are used to thicken the epoxy as thick as peanut butter. The alumilite product called deep pour also does it need a pressure pot. Top boat has several different epoxy/resin options. As for the pot, the California one is a good value. I suggest that you look at Robert Chatelain s work, he's retired and his original page is taken down. And also look at marilyn Campbell s work.

I haven't turned resin at all, (yet) but from my experience with model airplanes and epoxy, the addition of microballoons makes an epoxy finish much more workable. It looks powdery and disappears when mixed in, but creates micro sized (invisible) bubbles that makes sanding a lot easier.

 

[Joe Div]

Don Franks ---thanks so much, I was on that track you suggest! I have bought a small vacuum pot to degass and am now wondering which pressurepot and resin to buy make/size etc. I wouod love to hear your suggestion on that, keep in mind that this is a hobby for me not a business. I'm going to jusy have some fun and let any creative juices I have flow LO !!!!!!!!!!