Stabilizing Wood: Physics, Chemistry, Materials, Techniques, and Performance: "Just the facts Man"

[Stacy E. Apelt - Bladesmith]

Vacuum and then high pressure.

Just a comment on baking wood. 90-100°F/35-37°C in a drying cabinet will be OK, but get over 120°F/50°C and you start to make changes. The organic compounds and oils in wood will be changed by baking. Sugars will convert or carbonize. Oils and volatile compounds will evaporate, etc.. It can change color, hardness, texture, and become brittle. In some cases baked wood is nice - baked maple. I would not want to ruin thuya burl by baking it.

 

[WoodRush85]

Vacuum and then high pressure.

Just a comment on baking wood. 90-100°F/35-37°C in a drying cabinet will be OK, but get over 120°F/50°C and you start to make changes. The organic compounds and oils in wood will be changed by baking. Sugars will convert or carbonize. Oils and volatile compounds will evaporate, etc.. It can change color, hardness, texture, and become brittle. In some cases baked wood is nice - baked maple. I would not want to ruin thuya burl by baking it.

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[WoodRush85]

Your interpretation of what could happen seems right, but As I understand it, K&G does use a vacuum step before applying pressure, so a lot of the air in the pores does bubble out.

Re. Residual moisture, K&G does insist on and measure a minimum moisture content (10% ? Though I might be remembering slightly incorrectly.) if samples don’t meet that criteria, they say they put them on a rack in front of a fan until they do. Yeah, by baking the samples more moisture would be taken out, but that would add more time and expense to their process. Can’t really argue with success … perhaps they could get more resin into their samples … but my guess is they (consciously or not) decided their current approach is “good enough?

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[Jrmysell]

I don’t understand though how K&G is able to successfully stabilize if they’re not drying the wood beforehand. Turntex constantly tells everyone that you must bake your wood above 212 F until it stops losing weight or you will not have good results. So why doesn’t K&G’s resin bleed back out during the heat cure process if they have all that trapped moisture still in the wood?

The wood is dry. Less than 10% moisture content. It doesn't have to be 0%. Most that I have sent off were around 5-7%. Unless they bake then straight into the resin, they'll just reabsorb more moisture back to the 5-8% most woods stay at when dry.

 

[WoodRush85]

The wood is dry. Less than 10% moisture content. It doesn't have to be 0%. Most that I have sent off were around 5-7%. Unless they bake then straight into the resin, they'll just reabsorb more moisture back to the 5-8% most woods stay at when dry.

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[Stacy E. Apelt - Bladesmith]

Sorry for the poorly ststed post.
I may have used the wrong term, and too low a temperature in my statement. Different languages/areas/people may use the same terms to mean different things.
To me, Baking wood involves a longer time at high enough temperatures to change the wood structure. Drying wood involves putting the wood in a oven/kiln/oast to slowly allow moisture to be removed. drying can be done at temperatures up to the boiling point of water. Baking is done above that point. Baking wood is done as high at 400°F, IIRC.
The curing temperature that catalyzes the resin as part of stabilization is not what I was referring to.
Most stabilizers dry the wood a few days on a drying rack in a warm room for a few days if the moisture content is too high. There is usually a fan providing lots of air flow to speed the drying. This is not baking.

My point was that once you pass the point where moisture reduces by normal evaporation form the wood (the 120°F example I used) you can damage the wood by drying too fast or making changes that may affect the final product. Cracked and warped wood is the normal result from drying too fast or too hot.

 

[A.McPherson]

Then you’ve never stabilized at home using Cactus Juice or other readily abailable resins. They all tell you that you MUST dry your wood to “0% moisture” by heating it in an oven above 212 degF until it stops losing weight. You then have to seal it in an airtight container, ZIP lock bags, or vacuum shrink bags until it cools, then stabilize it. If you don’t then the moisture in the wood will affect the whole process and limit how much resin the wood can absorb and cause bleedout when you heat it to cure the resin. This is the reason for my question about how does K&G stabilize if they don’t remove all that moisture, when thousands of home stabilizers have been told for years that you MUST dry to 0%.

Call them and ask. They are pretty nice folks and will answer questions.

 

[WoodRush85]

Sorry for the poorly ststed post.
I may have used the wrong term, and too low a temperature in my statement. Different languages/areas/people may use the same terms to mean different things.
To me, Baking wood involves a longer time at high enough temperatures to change the wood structure. Drying wood involves putting the wood in a oven/kiln/oast to slowly allow moisture to be removed. drying can be done at temperatures up to the boiling point of water. Baking is done above that point. Baking wood is done as high at 400°F, IIRC.
The curing temperature that catalyzes the resin as part of stabilization is not what I was referring to.
Most stabilizers dry the wood a few days on a drying rack in a warm room for a few days if the moisture content is too high. There is usually a fan providing lots of air flow to speed the drying. This is not baking.

My point was that once you pass the point where moisture reduces by normal evaporation form the wood (the 120°F example I used) you can damage the wood by drying too fast or making changes that may affect the final product. Cracked and warped wood is the normal result from drying too fast or too hot.

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[WoodRush85]

Call them and ask. They are pretty nice folks and will answer questions.

 

[Jrmysell]

All of the people stabilizing wood at home with products like Cactus Juice are heating their wood to above 212 degF, usually around 220F. They weigh it on a gram scale throughout the process, and they bake it at 220 until it stops losing weight. This typically takes longer than 24 hours. Most of the stabilizing that is done involves baking at these temperatures, and there are a LOT of people all over the world doing it this way.

Even baking the wood like that I highly highly doubt you are getting a true 0% moisture content or like Stacey said you'll end up with cracks and warps. And there is a reason 99% of people on here will recommend professionally stabilizing from someone like K&G (or used to be WSSI as well) and not cactus juice. It's because the end product does not come out anywhere near as consistently. And like McPherson said, give them a call. They'll explain the what and why.

 

[WoodRush85]

Even baking the wood like that I highly highly doubt you are getting a true 0% moisture content or like Stacey said you'll end up with cracks and warps. And there is a reason 99% of people on here will recommend professionally stabilizing from someone like K&G (or used to be WSSI as well) and not cactus juice. It's because the end product does not come out anywhere near as consistently. And like McPherson said, give them a call. They'll explain the what and why.

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[weo]

I don’t understand though how K&G is able to...

I’m not going to call them

Well, then I'll politely suggest that you'll probably never get the answer to your question.

 

[Cushing H.]

I beg to differ. There are many Cactus Juice stabilizers who provide a very consistent product that’s as good as or better than K&G. And yes, there are lots of at-home stabilizers who don’t do a very good job. What I don’t understand is why Cactus Juice and all the other “at-home” resin sellers say you MUST dry as close to 0% as possible but K&G just throws it in at 5-10% moisture and it works just fine. I’m not going to call them as I don’t plan to send them any work, and it wouldn’t be right to pick their brain just to improve my process. I didn’t realize this was a “push K&G” forum, I thought it was for helping each other learn more about the process. I’m still hoping someone can explain how K&G can successfully stabilize at 5-10% moisture but the rest of the stabilizing world says you have to get to 0%.

Let’s keep comments clean and respectful folks…

Ok, let’s try this.

First you will never reach 0% moisture … the forces driving condensation are just too high.

Second, after you remove wood from the heated drying environment, it will very rapidly (read minutes, not hours) pick back up moisture, even in a dry environment. The forces driving capillary condensation are that strong. You would have to be extremely fast in going from the drying environment to the resin to avoid that reuptake. Plastic bags aren’t really that great at blocking moisture (that is why metalized bags were invented) … so saying you should take dry wood and seal them in bags is misleading, because after a short time the wood will not be as dry as when it came out of the heated chamber (and so what people think is “dry”, really is not.

Third: the residual moisture will be present in the very smallest of the small pores. Many of these, probably most of them, are smaller than the resin could penetrate to, even under pressure (reason - water VAPOR penetration is not hindered by surface tension, and so will penetrate to, and condense in, the very smallest pores. Since the resin never gets to that “depth”, the presence of that residual moisture neither impedes, nor “pushes out” the penetrated resin.

Fourth, per the discussion above, *even with moisture present in the very smallest pores* the use of high pressure to overcome capillary forces to drive the resin into smaller pores (and thus just plain get more resin into the wood) is something the home stabilizer could never accomplish. There might be something of an issue if the pressures used are high enough to get the resin into the very smallest pores where the residual moisture sits (and the moisture would then “block” the resin … ) but my guess is that is not the case, and with the moisture below some critical level (apparently somewhere around 8-10%) , the resin and the moisture do not compete for pores.

Fifth, people cite K&G as a benchmark because of their commercial success. I personally believe that it is really hard to argue with that, regardless of the technical reasons why.

 

[WoodRush85]

Let’s keep comments clean and respectful folks…

Ok, let’s try this.

First you will never reach 0% moisture … the forces driving condensation are just too high.

Second, after you remove wood from the heated drying environment, it will very rapidly (read minutes, not hours) pick back up moisture, even in a dry environment. The forces driving capillary condensation are that strong. You would have to be extremely fast in going from the drying environment to the resin to avoid that reuptake. Plastic bags aren’t really that great at blocking moisture (that is why metalized bags were invented) … so saying you should take dry wood and seal them in bags is misleading, because after a short time the wood will not be as dry as when it came out of the heated chamber (and so what people think is “dry”, really is not.

Third: the residual moisture will be present in the very smallest of the small pores. Many of these, probably most of them, are smaller than the resin could penetrate to, even under pressure (reason - water VAPOR penetration is not hindered by surface tension, and so will penetrate to, and condense in, the very smallest pores. Since the resin never gets to that “depth”, the presence of that residual moisture neither impedes, nor “pushes out” the penetrated resin.

Fourth, per the discussion above, *even with moisture present in the very smallest pores* the use of high pressure to overcome capillary forces to drive the resin into smaller pores (and thus just plain get more resin into the wood) is something the home stabilizer could never accomplish. There might be something of an issue if the pressures used are high enough to get the resin into the very smallest pores where the residual moisture sits (and the moisture would then “block” the resin … ) but my guess is that is not the case, and with the moisture below some critical level (apparently somewhere around 8-10%) , the resin and the moisture do not compete for pores.

Fifth, people cite K&G as a benchmark because of their commercial success. I personally believe that it is really hard to argue with that, regardless of the technical reasons why.

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[Stacy E. Apelt - Bladesmith]

I'll try and simplify the process. The dynamics in stabilizing wood are not the same as if it was a block of spongy metal.
First: The H2O in the wood is moisture absorbed into the wood, which is not the same as water soaked into the wood. The wood is dried to 7%-10% moisture content..
Second: The wood is submerged in a tank of resin. This is sealed and a strong vacuum is drawn. The vacuum removes most all the moisture remaining through sublimation, and also removes most all air. At this point the block of wood has internal low pressure where the air and moisture was removed.
Third: When the vacuum is released, the liquid resin forces itself into the wood at atmospheric pressure. No air bubble reform, nor does any water expand.
Fourth: High pressure compressed air, (many times what a home compressor can produce), forces the resin into the wood fibers. The resin impregnates the fibers where it is absorbed.
Last: When the pressure is finally released, the excess resin is poured off to be used again and the resin impregnated wood is put into a warming over to catalyze the resin. This forms long polymer chains that "stabilize" the wood.

 

[Cushing H.]

Thank you for taking time to respond. Your response is very helpful. If high pressure forces resin into the pores and moisture is also present, wouldn’t the water expand when it’s heated during the curing process and push the resin back out? That’s the part I don’t understand.

water itself will not expand really all that much. any REAL expansion would occur if the water turned to steam. looks like cactus juice is cured at temperatures below the boiling point of water ... so you will not see that really significant expansion of water into steam that would really displace resin.

Also, as things heat up, the resin will start curing - first becoming REALLY viscous, and then turning into a solid. either the really viscous resin, or resin as a solid, will be really difficult for any expanding water/steam to push back out of the pores....

 

[WoodRush85]

water itself will not expand really all that much. any REAL expansion would occur if the water turned to steam. looks like cactus juice is cured at temperatures below the boiling point of water ... so you will not see that really significant expansion of water into steam that would really displace resin.

Also, as things heat up, the resin will start curing - first becoming REALLY viscous, and then turning into a solid. either the really viscous resin, or resin as a solid, will be really difficult for any expanding water/steam to push back out of the pores....

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[Randydb]

Thanks to Cushing and Stacy for these explanations. This is not a K&G fan club forum. Over the years and experiences of of many many many knife makers K&G has produced really good quality stabilized wood for hundreds of builders at a great price. Basically it costs me about $6 cdn a block including shipping to get K&G to stabilize. On the other hand it seems like a good number of people have tried to do their own home stabilizing and only a small handful seem to have results that are verging on good. I think the majority of people end up going the simple route of the affordable, high quality consistent results that K&G produce.

 

[WoodRush85]

Thanks to Cushing and Stacy for these explanations. This is not a K&G fan club forum. Over the years and experiences of of many many many knife makers K&G has produced really good quality stabilized wood for hundreds of builders at a great price. Basically it costs me about $6 cdn a block including shipping to get K&G to stabilize. On the other hand it seems like a good number of people have tried to do their own home stabilizing and only a small handful seem to have results that are verging on good. I think the majority of people end up going the simple route of the affordable, high quality consistent results that K&G produce.

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[Randydb]

Thanks but there are many, many people who do amazing, high quality work with Cactus Juice. I’ll humbly include myself in that group. If you know what you’re doing it is an amazing product, and many knife makers use CJ stabilized blanks to create beautiful knives.

Post a picture of your set up John. I'm interested in what process and set up you are finding success with.