Thread: Vaccum infusion of friable wood

Originally Posted by BobL

If so then why you didn't mention the risks and mitigation thereof in your OP.

Then if you know something about OHS best practice, engineered solutions like a steel chamber or at least a mesh screen are generally superior to PPE like a face shield. A face shield should protect eyes/face but what happens to the rest of the newbie that decides to pick up a glass chamber under vacuum and the chamber decides to let go while they are holding it?

The risks are low but the potential damage can be high.

Bob,

Sorry for leaving out the safety stuff. For me most safety considerations go under common sense. OHS best practice is not my field I am involved in laboratory safety and a variety of vacuum operations associated therewith.

To All:

Other considerations on the vacuum chamber issue:
1) Keep the chamber size as small as practicable, less to implode means less stuff flying around if it fails.
2) Don't use thin wall glass containers like pickle, mason or jelly jars. Soda lime glass used in commonly encountered containers is too fragile for this kind of work. Containers made from it typically are not designed to contain pressure or vacuum. Drawing vacuum on one of these is very dangerous.
3) If possible use Pyrex or another high strength laboratory type glass - don't use tempered glass at all. Glass vacuum dessicators are availble on Ebay and if undamaged, see 6 below, are an ideal tool for this work if you are careful. Something like: Glass Desiccator Vacuum Jar Lab Dessicator Dryer 6" New | eBay
4) Check the chemical compatibility of all chamber materials including the chamber itself, fittings, pump and vacuum tubing.
5) Use vacuum tubing, not garden hose, latex tubing or any other expedient. Tygon vacuum tubing will save a lot of hassles in the long run.
6) If using glass be certain that it is not damaged in any way, even seemingly tiny scratches can be crack initiation points. So no scratches or chips of any kind can be tolerated.
7) Use containment as Bob counsels. A rudimentary expedient is to wrap outside of the chamber in fiber reinforced strapping tape. Ugly and it will give the safety inspector heart palpitations but it is better than nothing.
8) When under vacuum do not pick the chamber up or otherwise move it. You are already too close and by moving it around under vacuum you are inviting an accident.
9) No matter what, always use a face shield and safety glasses together. Do not take them off until the chamber is fully vented to atmospheric pressure or until you are on the other side of a wall or other substantial barrier.
10) All of this being said, I am in no way providing you life or limb preserving guidance and accept no responsibility for the comments posted here or anywhere else on the Internet. If you choose to mess around with electricity, sharp things, machines, welders, torches, vacuum or pressure chambers, chemicals or any other Darwinian selector out there you do so at your own risk.

Cheers,
Rob

Some good safety tips there Rob.

If only common sense was a common as we'd like it to be even on this forum but we just need to look at you tube to see how relatively rare it is.

Originally Posted by BobL

Some good safety tips there Rob.

If only common sense was a common as we'd like it to be even on this forum but we just need to look at you tube to see how relatively rare it is.

Hi Bob,

I don't know how the legal situation Re: tort liability is in Australia but here in the US the giving of safety advice can be a liability. For instance, if somebody follows my path on this vacuum work and gets hurt they could potentially sue me and recover because I was not explicit and totally complete in my warnings. Thus, in my posts, where I am almost always doing hazardous stuff, one should not take instruction. By making these posts I am simply documenting what I have done and lived to tell the tale. Your results may, and almost certainly will, vary. I have specialist knowledge of these things that keep me safer. If you are not a specialist you should not try to replicate what I am doing and if you do you do so at your own risk.
In other words: If you try this you may die or be seriously injured - I disclaim any and all responsibility for your actions.

Cheers,
Rob

Originally Posted by rob streeper

Hi Bob,

I don't know how the legal situation Re: tort liability is in Australia but here in the US the giving of safety advice can be a liability. . . . .

Fortunately we are not quite as litigious as the US (although unfortunately we are headed this way).
In Australia we are probably more likely to be sued for not providing any advice, than for providing some advice.
The advice I received from OHS lawyers/consultants about litigation risk where I used to work was to provide and implement "best practice advice" - not perfect but least litigiously risky than anything else.

The forum owners make it abundantly clear that all advice on these forums is of a general nature and users should seek expert advice outside these forums.
In some threads (especially those involving electrical work) you will see big bold insertions of posts about this by the mods.

I like to think knowledgable folk who post useful information on these forums will include appropriate safety advice.

There are some process points:

1. Consider the vacuum that you have to pull to get this done. Unless you're on top of an oil diffusion pump or a turbomolecular pump, you won't ever see much better than 10^-3 Torr, even with a top of the line rotary vacuum pump. My experience with infiltrating and embedding wood specimens suggests that several pulls and very, very slow air inlet will allow the air pressure to push the infiltrate further into the wood. Common vacuum pumps might give you 1(?)mmHg which is no screamin' Hello unless you have big bucks for a real pump.

2. Consider the anatomy of the wood itself: not all wood cells are open to the environment, not like an open cell sponge. Thus, two things: first, it will take some time for air molecules to find a path from inside the dry wood cells to the environment. . . . it takes time. You can stop pumping, hold the vacuum then pump again. Second, the infiltrate is made of far larger molecules and it will take much longer for these things to find a path into the wood. You can't hammer them in. 1 atm pressure is what you work with.

I spent several years researching the failures in grafting success with apple trees. Don't believe that I made any more than 2,000 microscope slides of embedded apple wood specimens. Histological wax is huge when compared with air. Epoxies would be similar. Given the time, most specimens would be adequately infiltrated (5mm) in less than a week. Block sizes were about surgar-cube in dimension.

The plastic bucket chamber is least likely to shatter. Any deformation due to ambient outside atmospheric pressure should make it leak like a sieve. We stored electron microscope film over phosphorus pentoxide in a glass vacuum-dessicator. The biggest mess was the dang vacuum grease on the rim to try to get the things to seal.

For those of you who have been following this story I decided to perform a test-to-destruction on the resin infused but already broken mesquite saw handle today. I repeatedly dropped the handle from waist height on concrete with no damage. I then did multiple drops with my arm extended overhead with the same result. Finally I tossed the handle in the air. It achieved about 15' altitude and broke on impact. Here is the result. The impact was directly into the lower horn and it sheared off the bottom section of the handle. Overall I rate this method as producing a handle that is pretty tough. It's also easy, relatively quick and inexpensive.

throw test.jpg

Originally Posted by rob streeper

For those of you who have been following this story I decided to perform a test-to-destruction on the resin infused but already broken mesquite saw handle today. I repeatedly dropped the handle from waist height on concrete with no damage. I then did multiple drops with my arm extended overhead with the same result. Finally I tossed the handle in the air. It achieved about 15' altitude and broke on impact. Here is the result. The impact was directly into the lower horn and it sheared off the bottom section of the handle. Overall I rate this method as producing a handle that is pretty tough. It's also easy, relatively quick and inexpensive.

throw test.jpg

Interesting Rob. From examining the fractured pieces of handle were you able to better determine the depth of penetration after using the vacuum impregnation process. Was this depth more or less than your initial expectations. How much of the outer skin hardening on the handle are you likely to then lose after later sanding prior to applying the top coat finish.

Stewie;

Thanks for the experiments, Rob. You can walk the walk.
I wonder how that handle would have performed in service, on a saw.
Do you imagine that you could have yanked and twisted on it until failure?

Originally Posted by planemaker

Interesting Rob. From examining the fractured pieces of handle were you able to better determine the depth of penetration after using the vacuum impregnation process. Was this depth more or less than your initial expectations. How much of the outer skin hardening on the handle are you likely to then lose after later sanding prior to applying the top coat finish.

Stewie;

These would indeed be very interesting to know.

With a porous material containing some moisture and maybe other volatiles, improved penetration may be achieved by repeated shorter pumping down sequences rather than than one long sequence.
By this I mean pump down and then expose back to air, repeat this 4-5-6 times and then perform the infusion.
The reason for this is that the back and forth pumping may better open up the pores and enable more "stuff" to infuse.
A weight check would enable this to be demonstrated

Originally Posted by BobL

These would indeed be very interesting to know.

With a porous material containing some moisture and maybe other volatiles, improved penetration may be achieved by repeated shorter pumping down sequences rather than than one long sequence.
By this I mean pump down and then expose back to air, repeat this 4-5-6 times and then perform the infusion.
The reason for this is that the back and forth pumping may better open up the pores and enable more "stuff" to infuse.
A weight check would enable this to be demonstrated

Hi Bob. The other issue that may cause some difficulties for Rob is that the Mesquite being used is also diseased wood. I would imagine very similar to what we call spalting. That being the case the pores of the wood may already be beyond expanding to there previous healthy wood size, preventing a good intake of infused resin. It would also be worth mentioning that this type of treatment would only work on certain open pored wood types. I am also unsure how this infusion would work on a lot of our Australian oily timbers. I also note that this infusion process is commonly used for pen making, where the center is hollow bored prior to this resin infusion. This step would most likely enhance greater penetration as a % of the timbers overall thickness. Not a possible option to consider with saw handles. I should include I have no previous experience with wood infusion.

Stewie;

I put the fractured handle under reflected illumination using a 480 nm UV 200 mW light, held the amber safety glasses over the lens of my iPhone and took some snaps. The limit of infusion is difficult to see in the photo but I measure about 3mm depth of penetration perpendicular to the grain and 8-9mm penetration along the grain.

filtered UV image.jpg

Here is an edited image indicating the approximate penetration that I can see by eye under UV illumination.

vacuum infused mesquite annotated.jpg

Originally Posted by planemaker

Hi Bob. The other issue that may cause some difficulties for Rob is that the Mesquite being used is also diseased wood. I would imagine very similar to what we call spalting. That being the case the pores of the wood may already be beyond expanding to there previous healthy wood size, preventing a good intake of infused resin. It would also be worth mentioning that this type of treatment would only work on certain open pored wood types. I am also unsure how this infusion would work on a lot of our Australian oily timbers. I also note that this infusion process is commonly used for pen making, where the center is hollow bored prior to this resin infusion. This step would most likely enhance greater penetration as a % of the timbers overall thickness. Not a possible option to consider with saw handles. I should include I have no previous experience with wood infusion.

Stewie;

This particular chunk of wood is quite sound. Mesquite tends to fracture along the grain following the annual growth rings. The heart wood is very resistant to fungus and is mostly subject to attack by ants. The sapwood is very liable to decay and on older logs the sap wood essentially falls off of the aged timbers. Mesquite also is very abrasive and tends to eat bandsaw blades, even TC tipped.

Originally Posted by Robson Valley

Thanks for the experiments, Rob. You can walk the walk.
I wonder how that handle would have performed in service, on a saw.
Do you imagine that you could have yanked and twisted on it until failure?

I did your test. I clamped the remaining chunk of handle in the vise as shown. First I tried to twist it. I could hear cracking but could not break it one-handed, I estimate approximately 100lb force applied. I had to tighten the vise mid-way because the handle started slipping.

twist and pull before 2.jpg

Then I flexed it from down to up. I estimate about 150lb lifting force applied. It broke at the weakest point. I rate it 'really tough'.

twist and pull after 2.jpg

Here are some shots of the test handle with finish. I sanded up through 280g, wiped on some BLO, applied shellac and wax and buffed. Looks better in person. The end shot shows that the Minwax wood hardener treatment did not affect the finishability of this wood under these conditions. Overall I am extremely pleased with the result.

after finish side shot.jpg

Severed end shot after finish.jpg