Wood Stabilization



I've got a bunch of scales from a great guy in New Brunswick, Canada. They are mostly maple burl, but some cherry and birch as well. I am okay with using them 'as-is' with coat of Beechwood-Casey Tru-Oil, but I'd like something more deeply set into the wood and by nature more durable. One option is to send them out for stabilizing. As of this posting date, there doesn't seem to be anyone offering this as a service in Canada. Many are selling stabilized scales, but none want to do other people's scales.

This started as a research project and now it's become a full-blown obsession.

Wood Stabilization Overview

The general process is to place the scales into some kind of vacuum chamber with a stabilizing resin and the air is evacuated from the wood. The resin is then allowed to penetrate the wood. Once the wood is saturated, it is removed and the resin is allowed to cure, often with the aid of heat.

Vacuum

In the home stabilizing field, anything from a hand operated vacuum pump, (for bleeding automotive brake systems) to a air conditioning service vacuum pump. The objective here is to create a vacuum of  around 25" of mercury or more, ideally 30".

Chamber

For the most part, home stabilizing is done in sealed jars, such as a pickle jar. The resin and pieces of wood are place into the jar (aka chamber), the lid is secured and a vacuum pump is attached.  

Resin

The magic is in the resin! I've learned of people using anything from Minwax Wood Hardener to polyurethane to methyl methacrylate. Everyone is super secretive about their recipes, so we won't find it easy to compare apples to apples. A popular choice is Minwax High Performance Wood Hardener, but this may be more due to availability than effectiveness.

Others include:


  • Cactus Juice Stabilizing Resin 
  • Stick Fast Stabilizing Resin
  • Resinol 90 
  • Pentacryl  

The bulk of these resins are acrylic. Some of these other solutions I have encountered are:

  • Plexiglas (acrylic) dissolved in acetone
  • Oil Based Polyurethane
  • Oil Based Polyurethane thinned with paint thinner
  • Polyurethane thinned with Acetone
  • Water Based Polyurethane

The MSDS for Minwax High Performance Wood Hardener states that it is 72% acetone, which leads me to believe some kind of acrylic is dissolved in the acetone.


My First Experiment

My first experiment is to try some pentacryl in the vacuum chamber and observe the results. I have some nice maple and piece of birch from my mate in New Brunswick.

My vacuum chamber, err...jar. Good old quart pickle jar with a 1/4" (1/8" ID) barbed hose fitting attached to the lid. This can be sealed however you like. I found a roofing washer (Aztec washer) and an NPT fitting. Make sure you use a tapered (NPT) thread if you are using regular brass to barbed fitting.

I have a Princess Auto 'Power Fist' brand brake bleeding vacuum pump kit.

Drill a hole in the lid to attach the hose fitting. Sealing can be as simple as rubber washer, silicone or what have you. Remember that a vacuum will exist inside, so the sealing force is going to be in the inward direction.
A short length of clear hose came with the vacuum pump connects the jar to the pump.

These are the three sets that I am going to stabilize.  On the left we have some spalted maple, int he middle there some maple burl and on the right some yellow birch.
More oxygen seems to be trapped in the burl and spalted pieces. Makes sense as these will be more porous.

Pulling about 15" and this is foaming heartily.
You may have to let the bubbles settle before adding more vacuum.










After the bubbles slowed down I worked the vacuum pump every 10 minutes or so to maintain the vacuum at about 24". I then let these sit overnight at room temperature.

The next morning the level of pentacryl had dropped in the jar. It looks like about 100 ml was absorbed.


















I placed some waxed paper down and removed the pieces to dry. All in all the Pentacryl is not very offensive to the nose, it's actually a little sweet smelling.


I will add more photos when I get to working up these scales into handles. I am curious to see how the pentacryl works and how deep it goes in under vacuum.
















UPDATE: October 7, 2014
I made another batch this time with heat cured acrylic that shows under UV light so we can check the penetration into the wood. A bunch of pieces were treated at the same time using the same vacuum pump and jar idea.

The stabilizing liquid is called Stick Fast and I have a gallon to play with. So far the treatment seems superior to pentacryl as it's "more plasticy." When I cut into some pieces I hope to show how the scale interiors are impacted by the product.

 One gallon of Stick Fast comes with a small bottle of catalyst. For the first trial I mixed at batch of 1/4 gallon and used 1/4th of the catalyst. This is a slight turpentine smell. Not really offensive.
 Put the scale into the jar and poured the Stick Fast in. Connect vacuum pump and had at 'er. Arms get pretty sore doing this as air is constantly being pulled from the wood and the vacuum drop as this happens.
 After observable bubbles stopped, I wrapped the wet scales in parchment paper. This is so they don't stick to each other in the oven. Into the toaster oven.

About an hour at 88°C (200°F). You can see the acrylic has hardened.













Update: This knife was made with the above shown scales stabilized with Stick Fast.

46 comments:

  1. Hi Dan, I'm just starting my own knife making journey, and while working at creating some sort of workshop out here (I'm welsh, but currently living in Southern Brazil), I'm really interested in gathering some interesting materials to make handles from.

    Do you know, or can you recommend any good information on the selection of timber, tree types and the drying of timbers? There seems to be a lot of really nice wood out here, but I'm not too sure how to dry it or treat it.

    Fantastic blog. Many thanks for sharing your knowledge. Ian

    ReplyDelete
  2. Hi,

    Normally with green timber, I would rip it into boards about 1" (25mm) thick and brush on some Pentacryl. Then stack them on stickers (battons or sticks) and let them dry in a place with good air circulation. The Pentacryl will prevent (or reduce) splitting when drying. It will take a while. I have some maple in my shop that is a couple years now and getting close. I don't know the specifics of the wood you are using and the environment there. I'd suspect it's pretty humid, so some form of heat may be required to speed things up.

    Best of luck!

    Dan

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  3. Hi Dan,
    Did you find the Stickfast in a homemade vacuum to be satisfactory? I am not aiming to replicate commercial stabilzing, just something to keep the wood from swelling and breaking.

    ReplyDelete
    Replies
    1. Yes, I am happy with the Stick Fast product. I was able to get good penetration with the hand vacuum pump (although it's lots of arm work) on all of the pieces I tried in the first batch. I am currently working on a knife with scales made from that stabilization batch.

      Delete
  4. Hi Dan we are trying to decide whether to try stabilizing wood blanks for pen making. We have found that the stabilized blanks from Lee Valley are excellent while some we got from a pen company don't seem to have the penetration and react just like regular wood (split, fall apart). What I am concerned with is that blanks for pens are anything from 3/8 to 1 inch thick and would we get the penetration that you get for your scales using a system like yours?

    ReplyDelete
    Replies
    1. Hi Brian,

      With the Stick Fast product I was able to get great penetration in softer and spalted woods. Hardwoods less, but still enough for 3/8" thick scales. The trick is to pull as much vacuum as you can and keep it up. It takes longer with the blocks, but can be done with 24 inches of Mercury.

      Sounds to me that the second pieces you bought are not stabilized using methmethacrylate. Perhaps they are done with a different stabilizer. The beauty of Stick Fast is that it shows under UV light. So you can cut a sample piece in half and check the penetration if you are not convinced. :-)

      Delete
  5. Hi thanks for this, really is,useful to me just starting out! Does the hand pump have a built in non return valve?

    ReplyDelete
    Replies
    1. Yes, it holds the vacuum. The drop in vacuum is caused by the air being extracted from the wood (bubbles) and needs to be pumped to maintain vacuum.

      Delete
  6. This comment has been removed by the author.

    ReplyDelete
  7. I have yet to use it (or do any stabilization at all actually) but I did find this stuff at my local home hardware.
    http://www.pcepoxy.com/our-products/wood-repair/pc-petrifier.php
    Nobody in town had the minwax.

    ReplyDelete
  8. I have some work experience using a vacuum to remove air from magnetic compass fluid after repair and renewal of the fluid which is usually an alcohol/water mix or petroleum oil. A jar full of the alcohol fluid will bubble away happily for several hours under a vacuum and I eventually realised that it was in fact boiling. Many solvents such as alcohol have a lower boiling point than water and what we often think of as air coming out of the fluid is often only the solvent boiling off. It is next to impossible to get 30" of vacuum with a normal pump- 25 to 28 is very good. I have experimented with old domestic fridge compressors and they work well at pulling this vacuum. There are usually two pipes coming out of the fridge compressor - one sucks and the other blows. You need a vacuum hose that is not going to be crushed by the vacuum on the suction side, (Automotive suppliers sell this). The exhaust side can be any cheap hose, and I would recommend venting it outside as any fumes from the solvents are possibly toxic. e.g. Hoppes No9 rifle barrel cleaner once smelt very nice, but they later had to remove the 'benzine' as it was found to be a carcinogen. I read once where people had experimented with wood stabilising using polystyrene foam packaging dissolved in acetone and that it worked well and that others have used slow drying gel super glue. Apparently even freshly cut wood can be stablilised - the process is more about removing moisture from the wood rather than about impregnating it with resin. It would be nice to think that the process gave full penetration of the resin but if you look at a commercially treated ground retention fence post the chemical doesn't penetrate very far. I would suspect that after shaping the handle there would be areas exposed that had no resin impregnated. You could test this by dyeing the resin before shaping. It might be an idea to stabilise the wood after it is fitted and shaped on the knife. There is always a risk when drying wood/epoxy using heat. I once made a beautiful wood knife handle and foolishly applied a fairly low heat to speed up the epoxy drying process. Several hours later the handle was split and ruined, and even the bond to the blade was broken.
    Great website you have here, many thanks for the ideas and plans.

    ReplyDelete
    Replies
    1. You are correct about being able to boil off different liquids like you did with alcohol. I use to do HVAC work and still have my pump. When you use your pump you are pulling all of the air out of the chamber including anything in it that is porous and the liquid is filling the negative space left by the air. If you continued to pull a vacuum you would start boiling off the components of the hardener. Also there is a difference between this and a fence post because where as this is vacuumed, a fence post is pressure treated. I've never done green wood before but I think I would place it in the vacuum by itself and boil off all o the moisture in it before I ever put my stabilizing liquid in it. May have to try it some time. Love the site.

      Delete
  9. Is there concern about hardener setting up in the jar? When I make makarta it starts setting up i8n about 30 min. (if I mix it right) Do you discard after one use?

    ReplyDelete
  10. Hi,

    The hardener doesn't solidify in air (or in a jar). It has a long shelf life. Stick Fast I believe can be used for up to 6 months after the catalyst is added to the resin. It is cured at about 200°F.

    Regards,

    Dan

    ReplyDelete
  11. Thanks for your blog. It's really helping me take my products to the next level.
    From what I can tell from the MSDS, Minwax wood hardener is polystyrene. I tried my first batch today, but I apparently have some leaks to locate. Keep the tips coming!
    Jonathan

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  12. Thanks for your blog, Dan. It's helped me out in so many ways. I've got my first batch of blanks in my jar this evening (mesquite with Minwax Wood Hardener). After patching up the leaks I'm maintaining about 21". I'll try to post the results.
    Jonathan

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  13. Could you use fiberglass resin for stabilizing the wood?

    ReplyDelete
    Replies
    1. Hi,

      I have not used it for stabilizing before. I would think that polyester resin is too thick to penetrate deep into the cells of the wood. Most resins I have played with have a water-like consistency.

      It wouldn't hurt to experiment. :-)

      Dan

      Delete
  14. I copied your method and it works great. My only problem is that the wood sometimes crack when curing in the oven. I use resinol 90. The wood has been stored inside my barn for 10 years before stabilization. Do you know what causes the cracks? and do you know how i can solve the problem. Thanks

    ReplyDelete
    Replies
    1. Hi Stefan,

      Cracking will occur if there any moisture in the wood, even moisture from the atmosphere.

      It is recommended to warm the pieces of wood in an oven, say 120°F (50°C) to rid the wood of inherent moisture and immediately seal the pieces in a zip-loc bag to cool back to room temperature. Once cooled they can go in to the stabilizing resin.

      Hope this helps,

      Dan

      Delete
  15. Hi Dan
    Thank you. I will try that. For how long would you recommend heating the wood, it has the size of a knife handle block.
    Stefan

    ReplyDelete
    Replies
    1. It depends on your local relative humidity. I live in a dry climate and so never had to heat dry any of my pieces. I'd suggest 1/2 hour per 1/2" thickness of material.

      Regards,

      Dan

      Delete
  16. Hi Dan
    Looks like you were right. I have just stabilized a piece. It went in the oven for 2,5 hours at 50° C and then in vacuum and then in the oven again wrapped in aluminium foil. Just took it out and I can't see any cracks. Thanks a lot. Looks like this is the way to do it.
    Stefan

    ReplyDelete
    Replies
    1. Excellent news. There must have been some moisture trapped in the wood and when heat curing it expanded and cracked the wood. I am glad you have had better success with the drying.

      Regards,

      Dan

      Delete
  17. How long did it take for the wood to stop releasing bubbles? I used plumbers putty to help hold the pressure at 25. Pin head bubbles have been rising off of the wood now for like 2 hours. the larger bubbles stopped about 30 minutes in.

    ReplyDelete
    Replies
    1. Ultimately, many factors would be involved in determining the time it takes, such as the porousness of the wood, thickness of pieces, vacuum, wood moisture content and resin viscosity and temperature.

      For the thin scale pieces I stabilize it takes about 30 to 45 minutes. If 0.1% of the air remains we're probably going to be all right. ;-)


      Dan

      Delete
  18. Hi, Dan! I was wondering is it possible to dye the stabilisation agent? I am going to try my first stabilisation experiment with pentacryl because there is nothing else available here. Can i dye it to make the wood more colourful? What kind of dyes are ok to use? Thanks for your super valuable and informative blog! This site is a treasure chest!

    ReplyDelete
    Replies
    1. Hi,

      If you are using Cactus Juice or Stick Fast, then Alumilite would be a good choice for dye. I've heard it takes repeat sessions to get that deep color into the wood. Also, once the resin is dyed, it will always be dyed.

      Dan

      Delete
  19. Hi dan

    I live in Ns and am looking for someone local to buy scales. Do you have the gentleman you buy from in New Brunswick email address?

    ReplyDelete
  20. Hi, Thanks for doing all of the experimenting. I am wondering how much difference being in a vacuum makes in absorption, vs just warming the wood and then soaking it in a stabilizer? Have you tried that?

    ReplyDelete
  21. I have tried soaking soft scale sized pieces overnight. The next day I applied some vacuum and there was still a lot of air trapped in the pieces. This may also show different results depending on the size and density of the wood. I don't think a simple soak would work well for denser woods or larger blocks as the resin needs help penetrating. Perhaps soaking for an extended length of time could equal using vacuum and/or pressure, but most of us don't have weeks to wait.

    It never hurts to experiment.

    ReplyDelete
  22. Hi Dan,
    Where can you get Cactus Juice or Stick Fast resins in Canada?
    Thanks

    ReplyDelete
    Replies
    1. Hi,

      I don't know of anyone carrying Cactus Juice in Canada. You will have to import in from the USA.

      I bought a gallon of Stick Fast from Woodchuckers in Toronto. Shipped via Canada Post. Give them a call as they sometimes don't show the different sizes on their web site: http://www.woodchuckers.com/

      Regards,

      Dan

      Delete
  23. Nice article, quick question... how did you treat the blade of the knife at the end of this article, to achieve that pattern?

    ReplyDelete
    Replies
    1. Hi,

      The Nakiri is made from carbon steel with oxidizes when in contact with acids. I used a small artist's paint brush and applied mustard and hot sauce for short periods of time until it had the effect I wanted. This is called a forced patina.

      Dan

      Delete
  24. Hello, I ran across your blog searching for info on stabilizing. I do scroll saw work and turnings.My daughter recently bought me a box of assorted pieces of wood. One of the woods is very porous and it was brought up to stabilize it. The friend that brought this up to me suggested I use a bag system to do it, kinda like with a seal of matic. Have you tried this type of stabilizing? Or know anyone that might have tried it? If not would you recommend this type of stabilizing and if not may I ask why?

    ReplyDelete
    Replies
    1. I have not used a bag or food saver vacuum system, although the Stick Fast company suggests this method for irregular shapes like turned bowls or large sized pieces that do not fit handily into a vacuum pot or jar. https://youtu.be/WGEQstQKLFs?t=17m3s

      Thanks for visiting!

      Dan

      Delete
  25. Thank you very very much. That was just what I needed.

    ReplyDelete
  26. How about the WEST resin ? It was created to penetrate wood used in boat construction. Also, would a seal a meal produce enough vacuum ?

    ReplyDelete
    Replies
    1. Hi William,

      I am a fan of West Systems epoxy, 105/206 and G-flex. I am not sure how well it would work as epoxy is usually quite viscous. The stabilizing resins I have played with are very close to the consistency of water. Maybe there is a way to thin epoxy with acetone or similar solvent to improve the penetration. I have not experimented with this.

      I've seen a special segment from StickFast regarding vacuum bags, however they are pulling a good vacuum with the same equipment they use in their can method. If you could connect a vacuum gauge and measure the food sealer. Anything in the 20 inches of mercury or better should do the trick on smaller pieces. The link is to YouTube just a couple of posts up.

      Regards,

      Dan

      Delete
  27. Hi Dan great blog! I’m in the Philippines and it’s very difficult to find any stabilizing products. Have you or heard of anyone using polyurethane floor varnish? That’s the only thing I can find here. A few questions sir:

    1: mix part A and part B before using it?
    2: can 8 just use part A and heat cure after?
    3 would sealer or topcoat be better?

    Thank you.

    ReplyDelete
  28. I’m plannng to use pieces of hardwood for my knife scales project. Also, I was thinking as the wood does not contract as much as the resin when switching to low temperature, would be an idea to warm up the resin and the jar then place them in the freezer with the wood inside?

    ReplyDelete
    Replies
    1. I am not sure I completely understand the process you are envisioning. The cooling of a sealed space will create a vacuum within the jar, but the viscosity of the resin would be increasing at the same time. Not sure if that would achieve the desired results.

      Dan

      Delete