Stabilizing hard woods in a HF PV pot

[Xephius]

Hi all,

This is my first post, but I have been lurking for a bit.

I recently built a HF PV pot, loosely based on the plans here. It holds pressure, but looses vacuum relatively quickly. I think I need to replace/add a seal to the top of the ports that go through the lid. They are designed to hold pressure, not vacuum and I suspect them to be the leak.

Anyway, on the subject of stabilizing hardwoods, has anyone done this? I am testing some walnut and purple heart at the moment to see how deep the stabilization mix (50% Polyurethane/ 50% Acetone) will penetrate in 24 hours of repeated vacuuming. I suspect the next question is "Why?!?"

I very much like the finish that I get from stabilized woods. It is fast, clean, easy and looks sharp when polished with micromesh. I have done a ton of CA finishes and I am unhappy with the delamination that happens at the ends, I have dipped, and that is nice, but messy and time consuming, but by far the best bang for my buck has been stablizied wood. So, I want to get that nice luster finish on a dense hardwood. Just curious if anyone else has done it...

Thanks,
-X


 

[Ankrom Exotics]

I stabilize hardwoods for a living. Walnut and purpleheart both stabilize very well.

A vacuum is an incredibly strong force and even my vacuum chambers will lose vacuum overnight. Here's my method.

1) place your blanks in whatever vessel you're using and place metal weights on top of them to keep them from floating.

2) add your stabilizing medium. Use enough to cover the blanks plus enough to allow total absorption without exposing the blanks to air when they're removed.

3) pull vacuum (your stabilizing medium will bubble and "boil" like crazy at first so use a large enough container that you don't spill over). Since you don't have a way to see what's happening I would pull the initial vacuum slowly, maybe 15-20 minutes to pull 25-29 inches of mercury.

4) keep the pump running for approximately 2-3 hours. This should be sufficient time on pen blank sized blanks of these species.

5) Remove from vacuum and allow to sit at normal atmospheric pressure overnight. Atmospheric pressure is plenty for all but the densest of woods. I only use the pressure pot for stubborn species like Amboyna and some of the Australian burls.

6) I use a heat cured medium for my stabilizing so I would bake my blanks for 2 hrs at this point but you will need to remove yours from the liquid and place them on a rack and allow them to air dry. I would guess for probably a couple weeks, give or take.

A final word of caution. A few years ago when I was just experimenting I ruined a vacuum pump by using acetone in my stabilizing solution. Acetone vapors alone will dissolve plastic and apparently my pump had some internal plastic parts.

Anyway, I hope this info is helpful to you and I wish you good luck with your experiment.

 

[holmqer]

Pat provided an excellent write up. If you are going to stabalize with Polyurathane, I would suggest thinning with Mineral Spirits instead of Acetone.

 

[Xephius]

Thank you both for you advice, I have a couple of follow up questions.

buzz7164,

I currently have my 2.5 gal pot filled with 2 gal of liquid. Would I be better to reduce the amount of fluid to the minimal amount (I assume to provide more air volume to remove and possibly be replaced with volume from the wood), or leave the larger amount of liquid and just fish out the blanks when I am done?

When I do use pressure to stabilize things such as Amboyna burl, what is the suggested procedure for that?

What heat cured solution do you use? Is it available to be purchased on the web? I would far prefer to bake my blanks for a couple hours than let them sit for a couple weeks.

Thanks for the tip on the Acetone fumes, I am currently using a venture "pump" so no moving parts to destroy. But when I do get a real pump I will remember the tip!

holmqer,

Can you point me to the write up from "Pat"? I searched the forums when I first started my build and don't recall anyone suggesting Mineral Spirits over Acetone. I only went with acetone because that is what was suggested in the thread I was reading..
What is the reason for Mineral Spirits over Acetone? Do I need to chuck my current batch of materials, or is it usable and just switch next time?

Thanks,
-X


 

[Jim15]

Thanks Pat.

 

[Ankrom Exotics]

Xephius,

Are you filling your pressure pot directly with the stabilizing solution? If so, I'd like to make a suggestion.

Use a seperate container of some sort such as a tupperware container or a coffee can (another advantage of NOT using acetone is the abilty to use plastic containers without melting or softening them).

Put your blanks in these containers and apply the weights and then cover with the solution.

Place a container in the pressure pot and stabilize as described in my first reply to this thread.

There are two advantages to this. First, you keep the pressure pot clean (critical for me as I sometimes use dyes). Second, you can remove the container and get another batch under vacuum while the first is obtaining equilibreum.

When stabilizing species that benefit from additional pressure simply add air pressure to the pressure pot and let it stand for a day or two.

I use Resinol 90C as my stabilizing medium. I purchase directly from Henkel-Loctite but there is also a retailer on ebay. Search "Resinol 90C". You should know that it needs to be refrigerated in a dedicated refrigerator (nasty stuff.... DO NOT store in a frig that you keep food in) and has a very short shelf life at room temp. You will also need a dedicated oven for the curing process. Don't do it where ya bake your taters.

I believe that holmqer was referring to my initial reply to this thread as the "write up". When I have the time I hope to write a complete tutorial for the library.

Again, I hope this info is useful and good luck. Keep us posted as to your results.

 

[Xephius]

Pat,

Thanks for the advice. I will clean out my pot today and change the setup. I will look into Resinol, but it does seem to require some dedicated equipment. Would there be a problem with sharing the oven with my powder coating projects or as an annealing oven with metal? If not, then it is just another reason I need to hook up the oven in the garage.... This really has been a great write up, I will post pics when I pull the blanks.

-X


 

[KenV]

Remember that solvents boil (vaporize) at low temperature and solvents like acetone are boiling at very low temperatures. As pressure decreases (vacuum) the boiling poiint is lowered and you are pumping acetone vapors out through the vacuum pump. Smell pretty strong of solvent --- so do not light a match and keep it away from flames (hotwater heater, funace, lanterns, etc.)

You will boil off the solvents before you pull much air out of the wood.

The reason for the solvents is to lower viscosity (thickness) and the surface tension (ability of the resin solids to catch to the wood surfaces).

PR resins are not solvent based -- and are much less sensitive to boiling off solvents.

 

[holmqer]

Thank you both for you advice, I have a couple of follow up questions.


holmqer,

Can you point me to the write up from "Pat"? I searched the forums when I first started my build and don't recall anyone suggesting Mineral Spirits over Acetone. I only went with acetone because that is what was suggested in the thread I was reading..
What is the reason for Mineral Spirits over Acetone? Do I need to chuck my current batch of materials, or is it usable and just switch next time?

Thanks,
-X


I was referring to Pat's initial response to your question.

I recommended Mineral Spirits for two reasons, first all the oil based Polyurethane cans I checked listed Mineral Spirits as a thinner / cleanup agent, and second it has a much lower volatility than Acetone, making it safer, and is also less likely to cause miscelanious things in the vicinity to melt.

 

[RBoutin]

If you have a small number of blanks and you don't want to risk ruining an oven, go to the grocery store and buy Ziploc vacuum bags with the little plastic vacuum pump. You can fit 2-3 pen blanks in a bag. Suck just enough air out so the bag collapses around the blanks and contacts all surfaces. Then place the bag into a pot of water at just under boiling for half an hour. Good if you have a basket or rack to keep the bag off the bottom. Works like a charm.

Pat,

Thanks for the advice. I will clean out my pot today and change the setup. I will look into Resinol, but it does seem to require some dedicated equipment. Would there be a problem with sharing the oven with my powder coating projects or as an annealing oven with metal? If not, then it is just another reason I need to hook up the oven in the garage.... This really has been a great write up, I will post pics when I pull the blanks.

-X


 

[Xephius]

Thanks everyone for the input and advice. I cleaned out my pot, and will convert to a better solvent/stabilizing mix next batch. I am fairly sure I will rock through this batch as I also hope to stabilize some larger bits of wood for bowl turning.

I will also keep an eye on the vapor fumes, and the viscosity of the mix.

-X


 

[GouletPens]

Pat, you mentioned pulling vacuum for 15-20 minutes, but with a sealed container like the HF PP, does the draw need to be continuous like that, or could you pull 25 inches and seal the pot to get the same result?

 

[SherryD]

I would add that it is easier to control if you use a vacuum chamber that has a clear lid so you can control the dry vacuum feed thru. Much easier to control the feed of the stabilizing liquid if you can see what you are doing. Granted a dedicated vacuum chamber is pricey but if you do any significant quantity it will pay for itself in 3o days or less. I use the pressure pot for second stage of dying, not stabilizing. I also have used Resinol 90C but am going to try the Ultraseal product in the next week.

 

[Ankrom Exotics]

I pull a continuous vacuum when I stabilize, usually for several hours. I have 1" thick plexiglas lids on my vacuum chambers so I can keep an eye on things and when I close the valves and shut off the pump the bubbling tends to completely stop within a couple minutes or so. When I turn the pump back on and open the valves the bubbling continues.

I've tried both ways and a continuous vacuum seems to be more efficient.

Pat, you mentioned pulling vacuum for 15-20 minutes, but with a sealed container like the HF PP, does the draw need to be continuous like that, or could you pull 25 inches and seal the pot to get the same result?