Thread: Vaccum infusion of friable wood

Can you eyeball the depth of penetration into the wood from your test cuts?

Just asking, 'cos 25-30 mins is an awfully short time when it comes to vacuum work, however I haven't used Miniwax Wood Hardener, nor do I have any idea of the properties of mesquite in this situation; I mainly work with epoxy & Aussie HW where "overnight" is a more effective measure of time scale.

Hi Rob,

Thanks for posting that, I just realized that I have a vacuum tank and good vacuum pump sitting on the shelf.. my son used it when he was doing plastic molding.

I guess the time for complete penetration would depend on viscosity and how porous the timber is..

Ray

Originally Posted by RayG

Hi Rob,

Thanks for posting that, I just realized that I have a vacuum tank and good vacuum pump sitting on the shelf.. my son used it when he was doing plastic molding.

I guess the time for complete penetration would depend on viscosity and how porous the timber is..

Ray

...possibly ambient temperature too.

Keep us informed of progress rob, looks interesting. I could think of a couple of applications myself.

I watched a demo with Cactus Juice at the last penturners get together at Sturdee's place.

It was using Cactus Juice, imported from the US

TurnTex Woodworks - Cactus Juice Stabilizing

and sold in Oz by Mark at 043Turning.

Quite impressive results on punky timbers.

On another forum site Dominic Greco used Minwax Wood Hardener as the resin to vacuum impregnate some punky timber with the following results.


Eric,
To answer your question, and to echo the reply of some others here, Yes you can make a vaccum chamber and "resin" impregnate your own tool blanks. I've tried it and the results were OK. Not great mind you. Just OK. Back when I was turning pens this seemed like a good idea to make premium blanks out of punky wood.

You need a vacuum pump that can pull about 25" Hg. I have one and use it on my lathe as a vacuum chuck. Then you need a vacuum chamber. I used an old pickle jar. The test piece was some spalted silver maple that had the consitency of styrofoam. But the color was amazing! I used Minwax Wood hardener as the "resin" but other have actually used melted plexiglass (in acetone). I adapted the lid of the pickle jar with some fittings and made sure it sealed well. Then I got an old soup can, put a wire handle on it, and then filled it with the maple test piece and the wood hardener. As soon as you pull a vacuum, the test piece started to suck up the hardener. I maintained the vacuum for a couple hours and then allowed the piece to dry. After it dried I found that the hardener only penetrated about 1/8' to 1/4" into the wood. I was told that drilling a hole right up through the center of the test piece (as mist pen blanks have this anyway) would help. I never tried that but reasoned it would work.

After all this mess I shelved the vaccum rig and haven't touched it since. However, your idea of using it to make chisel handle blanks has peaked my interest. You could probably drill a small diameter "stopped" hole up the middle of the blank and that would allow the "resin" to infuse more of the blank.

Originally Posted by Skew ChiDAMN!!

Can you eyeball the depth of penetration into the wood from your test cuts?

Just asking, 'cos 25-30 mins is an awfully short time when it comes to vacuum work, however I haven't used Miniwax Wood Hardener, nor do I have any idea of the properties of mesquite in this situation; I mainly work with epoxy & Aussie HW where "overnight" is a more effective measure of time scale.

It is very hard to visualize. I cut through the area just behind the saw plate mounting region, smoothed off the surface and applied denatured alcohol to the clean surface. Based on the pattern of evaporation I can see that the penetration is roughly 4 mm from all surfaces exposed to the wood hardener solution. Since the region that clamps onto the blade is one of the more likely places for damage to occur during manufacture I think 15 min infusion will work fine. I made test cuts in various areas of the handle and the wood behaves much better under file and rasp with less tear outs and a very perceptible increase in hardness.

The Minwax product is an acetone solution. In infusing this test piece I cut the stock hardener back about 50% with acetone to decrease the viscosity.

Overall, I am very pleased and it now seems, pending a test of finish-ability, that the Minwax product will make mesquite much more useful for saw handles.

Originally Posted by rob streeper

It is very hard to visualize. I cut through the area just behind the saw plate mounting region, smoothed off the surface and applied denatured alcohol to the clean surface. Based on the pattern of evaporation I can see that the penetration is roughly 4 mm from all surfaces exposed to the wood hardener solution. Since the region that clamps onto the blade is one of the more likely places for damage to occur during manufacture I think 15 min infusion will work fine. I made test cuts in various areas of the handle and the wood behaves much better under file and rasp with less tear outs and a very perceptible increase in hardness.

4mm? That's a respectable depth, given the vacuum time.

I have given some thought in the past to doing short (as compared to "overnight" ) sessions, shaping down 'til "fresh" timber is exposed and then repeating the process, terminating in one final vacuum session once the timber is fully shaped.

Admittedly 'tis more labour intensive, but your input - & info I've gleaned elsewhere - suggests that it'd shave days off my current process, from start to finish.

Overall, I am very pleased and it now seems, pending a test of finish-ability, that the Minwax product will make mesquite much more useful for saw handles.

That's the important thing; that you're happy with the results. I'll be keeping an eye on this thread to see how you feel about the finish-ability... from the browsing I've done on Miniwax Wood Hardener it appears that it's not water-proof & tends to turn milky (similar to shellac) if wetted. Which may - or may not - be a problem. Not a criticism of the product, just an observation and not really relevant to your original post.

Thank you for the feedback and here's to hoping your saw handle is a total success!

Originally Posted by RayG

Hi Rob,

Thanks for posting that, I just realized that I have a vacuum tank and good vacuum pump sitting on the shelf.. my son used it when he was doing plastic molding.

I guess the time for complete penetration would depend on viscosity and how porous the timber is..

Ray

Hi Ray,

The bubbling largely stopped at 15 minutes. I tapped the container to get bubbles that adhered to the surface of the wood to detach them and closed off the pump valve after another few minutes. I could only draw about 22 in. Hg because of the acetone solvent. I have a vacuum leak valve in the top plate that allows me to slowly vent the chamber. I allowed the handle to sit for about 10 minutes under vacuum and then vented it.

Cheers,
Rob

Well, timely post indeed. About a year ago I looked into this process for some saw handles and turnings. Things got busy and the research was shelved. Last spring I got a close look at some chisel type handles Blue Spruce had infused. I liked the results and finally, about a month ago, got around to sending various wood samples off to be infused. Including fidddle back mahogany, sycamore, Tiger maple, etc. If I ever get this stuff back I will let you know the results. Take care, Ron

I would like to warn anyone making a vacuum chamber out of glass of the potential dangers.

If the glass breaks there is the danger of an implosion whereby the glass collapses onto itself and and then explodes outwards sending shards of glass at VERY high speed.
In laboratories that use glass vacuum chambers, this is treated as a very serious OHS risk.

It does not matter if one is really careful, sometimes all it needs is a gentle tap against the chamber or placing the chamber under vacuum onto an uneven surface so the glass experiences a slight stress.
The glass may also already have a microcrack in it and be a ticking time bomb in this regard. Repeated use of the chamber may also eventually generate such a crack leading to this effect.

Most of the time the glass will just crack and lose vacuum but it's not worth the risk of an implosion.

To mitigate against such an explosion a metal screen/cover placed over the top of the glass container before the vacuum is applied is a requirement in a laboratory.
The screen should also of course only ever be removed once the vacuum has been released.

A screen made of tough Al security mesh would be OK for small chambers, but for bigger chambers steel mesh should be used.

A solid steel chamber is the safest. If visual is required a piece of thick security glass (two layers of glass sandwiching a layer of flexible plastic, OR single layer layer of glass covered on both sides sides with quality security film) can be used in conjunction with a rubber seal. The thickness of the glass depends on the area of glass needed. As a guide a 100 x 100 mm viewing port should use at least 12 mm thick glass.

An no you cannot just cover a glass container with security film.
Most glass containers are too thin and too stressed to be secured in this way.

Originally Posted by BobL

I would like to warn anyone making a vacuum chamber out of glass of the potential dangerous.

If the glass breaks there is the danger of an implosion whereby the glass collapses onto itself and and then explodes outwards sending shards of glass at VERY high speed.

It does not matter if one is really careful, sometimes all it needs is a gentle tap against the chamber or placing the chamber onto an uneven surface so the glass experiences a slight stress.
The glass may also already have a microcrack in it and be a ticking time bomb in this regard. Multiple uses of the chamber may also eventually weaken the glass leading to this effect.

Most of the time the glass will just crack and lose vacuum but it's not worth the risk of an implosion.

To mitigate against such an explosion a metal screen/cover placed over the top of the glass container before the vacuum is applied is a worthwhile safety procedure.
The screen should also only be removed once the vacuum has been released.

A screen made of tough Al security mesh would be OK for small chambers, but for bigger chambers steel mesh should be used.

A solid steel chamber is the safest. If visual is required a piece of thick security glass (two layers of glass sandwiching and layer of flexible plastic, OR single layer layer of glass covered on both sides sides with security film) can be used in conjunction with a rubber seal. The thickness of the glass depends on the area of glass needed. As a guide a 100 x 100 mm viewing port should use at least 12 mm thick glass.

An no you cannot just cover a glass container with security film.
Most glass containers are too thin and too stressed to be secured in this way.

What about the polycarbonate or acrylic containers??

Originally Posted by DSEL74

What about the polycarbonate or acrylic containers??

Yep - safer but not fool proof.
They can also be used more safely as viewports for steel chambers.
Small chambers should be made from a minimum of 12 mm thick acrylic and large chambers of 1" thick.
PC can be thinner but I don't know how much thinner.

Thick material is used to ensure very high vacuums and for safety reasons.
However, there is not much difference in the safety implications of 24" or 29.9" of mercury.
Even a vacuum of 20" of mercury can cause an implosion.

Some info and ideas here
Acrylic Vacuum Chambers from Terra Universal
Vacuum Chamber - Full-view Acrylic
Plenty of ideas on youtube - not all of them are safe in my book.
This one looks OK.
How to make a homemade vacuum chamber for degassing silicone - YouTube

NB long term Acrylic must also be kept away from UV and daylight.

Originally Posted by DSEL74

What about the polycarbonate or acrylic containers??

Polycarbonate and acrylic are fine for water based products but don't use them with the Minwax product or any other product that is dissolved in acetone. That's why I made my top out of Delrin - it's essentially acetone proof.

As to the implosion hazard, I know the risks very well as I have a lot of high vacuum work experience, where do you think my fancy fittings come from? No matter what, when working with low or high pressure chambers always use a face shield and safety glasses together.

Originally Posted by rob streeper

As to the implosion hazard, I know the risks very well as I have a lot of high vacuum work experience, where do you think my fancy fittings come from? No matter what, when working with low or high pressure chambers always use a face shield and safety glasses together.

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.