Please read the new sticky announcement here for full details.
Discussion in 'Woodturning Discussion Forum' started by Tom Albrecht, Dec 3, 2017.
Does anybody here have any knowledge or experience building a vacuum chamber for stabilizing wood?
No but the guys who sell Cactus Juice sure do have a nice one.
They do, but I always try on my own first.
I saw a demo about 2 years ago where a guy used a hand vacuum pump used for wine to stabilize small pieces suitable for ornaments, jewelry, pens etc.
I’ve seen where somebody took a thickwalled glass cookie jar and made a vacuum chamber with it. I tried it using a turned wood lid with silicone caulk seals. It worked but the wood leaked vacuum a bit and the seal was unstable. If you can get past these technical problems you got it made.
Yes, I used a paint pot. I stripped all the fittings and replaced them with a vacuum gage and a quick connect to attach to my vacuum pump. The only issues I had was I couldn't see inside during the process. So, a friend of mine had some 1 inch thick clear plastic (acrylic?). I turned two lids, one for him and one for me, drilled and tapped for pipe threads and was in business. So far it has held up altho it has only been thru seven or eight cycles. Right now the vacuum holds the lid on (turned a grove to hold the gasket (no glue)). I had thought of modifying some C-clamps so I could pressurize after vacuuming but haven't yet. I put the wood and solution in a pot that fits into the pressure pot, makes clean up easier. I had most of the plumbing parts stashed, but bought the pressure pot and the NPT tap from the cheap tool store, using the 25% off coupon...
You can use a large heavy glass cookie jar if you want to see the process working.
A 1/4" or thicker piece of acrylic can be used for the top, a gasket can be made of silicone
or rubber to seal around the rim of the jar. You could use a heavy glass lid but drilling a hole
in the glass for your vacuum line can be a challenge for many people.
An easier solution is a Harbor Freight pressure spray pot used for painting, these are quick
and easy to modify for a vacuum application. Another easy retrofit is a large pressure cooker
that has a seal between the cooker and lid.
Curtis Seebeck is the Cactus Juice guy. I have a feeling that it would be more practical (save time and maybe cost less) to just buy a ready made vacuum chamber from him or one of his competitors unless you just happened to have most of the stuff that Clifton mentioned. Curtis originally built rectangular vacuum chambers using very thick plexiglass and solvent welding the pieces together. That required perfect precision in cutting the pieces. Now he sells cylindrical chambers which is a better solution and also less expensive.
The upside to the pot use is you can work on bigger pieces. A small rough turned bowl will fit or you can use a vacuum bag if you can avoid sharp edges puncturing the bag and have an intermediate separator jar on the vacuum line.
I have both a turntex one great for my long stuff up to 8 inch round. And a best value vac one. It's a 12 inch round aluminum one by about 12 inch deep with a 1 inch thick glass top. Need the glass lid for resin, will not warranty acrylic lid for resin . Comes with gauges and everything for 100$ . Sweet for large rounds. And I'm in Canada.
I took a Dutch Oven form the kitchen, it's 11" diameter and about 5" high to use as the chamber. Then a piece of 3/4" Plexiglas (Amazon about $25) and threaded it to accommodate a 1/4" Air Barb (Ace $1.90)....For a seal I used a piece of smooth form sheeting that a TV we bought was wrapped in (smooth -- not the bubble kind). I use that form sheeting for my vacuum chucks also. Works Great. Warning though, at first I used a 3/8" Plexiglas and it imploded after a few weeks use. The 3/4" seems to be thick enough.
The OP (Tom) asked about stabilizing in a vacuum. I assume that refers to impregnating with resin.
What about drying wood in a vacuum chamber? Practical? Anybody doing it? I know water boils at lower temps in a vacuum, not sure though how well that works with wet wood.
Your reference to Best Value Vacs is good. Turns out they are about 45 minutes from me. It was good to call them and find out that the Glass top is the preference over either of the Plastic tops. He said that the wood stabilizing liquid will ruin the plastic tops right away.
That said, are there other sources for the stabilizing juice besides TurnTex?
Pulling a lot of moisture through a vacuum pump can cause problems. If it is a dry vane pump, your vacuum may not be high enough. If it is an oil pump you can contaminate your oil which will reduce you max vacuum and require an oil change. In both cases there is also the possibility of rusting the pump. In either case, unless you trap the moisture before it gets to the pump, it's not a good idea.
Thanks Dave. Good information.
I have both oil-less and oil type vacuum pumps. With the oil-less type when moisture was sucked in my pump became a fog generator. When it happened the pump head got very hot and locked up. Assuming the pump was destroyed I shelved it. Later, before throwing it out I tried running it again it and it performed as if there never was a problem. ???
I was planning on adding a water filter to the inlet side of my vacuum pump similar to what I use on my compressor to trap the water. I've never tried that so not quite sure how effective it'll be. Not even sure how much moisture the vacuum pump can tolerate without problems.
Aside from the moisture problems with vacuum pumps do you have any thoughts on drying wood with a vacuum chamber? Googling on the subject brought up responses, it seems heating the vacuum chamber is good. Still, I'd like to hear some first hand experiences.
Think about safety implications also. A vacuum chamber has fewer potential hazards than a pressure chamber (you're limited to 14.7 psi, or 101,325 Pa of pressure, unless you live below sea level)--nevertheless, you have all that atmosphere pressing on the chamber. When glass fractures, you'll get lots of shards--fewer shards with fracture of acrylic (lucite, plexiglas), polycarbonate (lexan), or polyester resins. Corners and other changes in geometry introduce stress concentrations (the corner sees a higher stress). Think about putting your vacuum pot in a second container before sucking.
Vacuum pumps that we typically buy are not intended for continuous duty use. Think about sucking down to some level of vacuum, then, duty-cycling the pump (off for a while, on for a while). A moisture filter will typically collect condensing (or condensed) water, but not vapor. A moisture filter that includes a silica gel will absorb vapor-phase water, but the silica gel needs to be replenished periodically (you can bake it out). Silica gel that has a blue color contains traces of either chromium or cobalt salts (I don't remember which), and the Europeans have decided that this salt is hazardous. Bake out when the blue has changed color, it will return to blue.
Heating the vacuum chamber: We typically do this for high vacuums (really sucks ), to force the metal walls to release adsorbed layers, but we're talking serious temperatures (sufficient to roast a chicken).
My guess is that removing moisture from wood should be a relatively slow and gentle process, not a high speed process--but that's a guess. Remember that moisture will want to escape through the end-grain much faster than it wants to escape from other directions.
A couple issues with greatly accelerated drying are case hardening and cell wall collapse. Whether they are a problem for you depends on the wood species and how you plan to use it.
When your accumulation of wood gets large enough, drying it generally ceases to be a problem.
I'd like to get back to my original subject here...
Are there other sources for stabilizing juice other than Turn Tex?
I first used the TMI product from WoodCraft called Stick Fast Stabilizing Resin, then went with Cactus Juice. It might be the same stuff, it's just that TurnTex has so much info on his website and, if you call, you talk to Curt, owner, operator, turner... I like that...
From my understanding cactus juice is the original and stickfast got that product reverse engineered and put out stick fast. A copy. ( only costs 25,000$ to do it. ) I could be wrong .