Recommendation? Wood stabilizing under pressure

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PavelKa

Joined
Jan 29, 2019
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Hello, I am trying to stabilize wood with epoxy resin in vacuum chamber. Unfortunately vacuum is not enough, it is not working for harder woods... so I wanna try to forced resin by pressure -> firstly vacuum stabilization, wood is completely submerged in resin and after that pressure -> pushes resin deeper into the wood. Does anybody know, what pressure is necessary/optimal? 70PSI? is it enough? mabe more or less?
thank you for any advice,
Pavel
 
I don't see where you would get much benefit from the pressure application. As soon as you took the pressure off, it would equalize back to atmospheric & push out whatever stuff you pushed in there to begin with. Unless you let it cure under pressure, but that doesn't seem very practical.

What epoxy are you trying to use?

I saw this stuff: https://www.systemthree.com/products/clear-coat-low-viscosity-epoxy-sealer
...and was pondering trying to stabilize extremely soft & porous stuff and wondered if it would work under vacuum. Things like thick tree bark, rotten wood, coconut husk, etc...
 
Sam Dean said:
I don't see where you would get much benefit from the pressure application. As soon as you took the pressure off, it would equalize back to atmospheric & push out whatever stuff you pushed in there to begin with. Unless you let it cure under pressure, but that doesn't seem very practical.

What epoxy are you trying to use?

I saw this stuff: https://www.systemthree.com/products/clear-coat-low-viscosity-epoxy-sealer
...and was pondering trying to stabilize extremely soft & porous stuff and wondered if it would work under vacuum. Things like thick tree bark, rotten wood, coconut husk, etc...
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I've been doing this for a while and have never had a complete vacuum cycle under 5 hours. Epoxy will harden before then. Why not just use the correct product?
 
Kevin McGovern said:
I've been doing this for a while and have never had a complete vacuum cycle under 5 hours. Epoxy will harden before then. Why not just use the correct product?
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No clue. Personally, I have ZERO experience with stabilization, so I'm sure you're correct.

I added the comment and link because I thought it would be interesting to "stabilize" things that are extremely soft and unstable, with large voids and inclusions, and had previously wondered if epoxy is a viable option.

Would cactus juice work on something like coconut husk? Or soft palm wood?

Aside from that, from what the OP asked, I still don't think pressure would provide any benefit...
 
Sam Dean said:
No clue. Personally, I have ZERO experience with stabilization, so I'm sure you're correct.

I added the comment and link because I thought it would be interesting to "stabilize" things that are extremely soft and unstable, with large voids and inclusions, and had previously wondered if epoxy is a viable option.

Would cactus juice work on something like coconut husk? Or soft palm wood?

Aside from that, from what the OP asked, I still don't think pressure would provide any benefit...
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Palm wood can be stabilized. Coconut husk could be stabilized then cast in resin
 
You start with vacuum and end with pressure. It takes a very good vacuum pump and chamber to get good results. It also takes a couple hundred pounds of pressure. This is why the professionals, like K&G, are the people to send it to. They have the right resins and the right equipment.
 
Think through the perceived need for pressure and you'll see that pressure isn't needed. It can speed up the soak time after vacuum, but will not increase penetration. Resin will only enter spaces that have been evacuated of air. Since nature abhors a vacuum, once the vacuum is released, the space WILL be filled. Any pressure exerted after the piece has had ample soak time, is pointless. Since any resin pushed into the piece under pressure will come out as soon as the pressure is released. this is because pushing resin into a void at atmospheric pressure will cause a high pressure condition in that void and releasing pressure (which you must do to cure the piece) will result in the equalization of pressure between the void and the open atmosphere.
 
It makes total sense that k&g would use pressure to speed up the soak cycle, since that cycle is longer than the vacuum cycle. And time is money. If a home stabilizer is PATIENT, and allows the time needed in the soak ( at least as long as the vacuum time, I do at least 2x as long) you will have proper penetration. No need for pressure .
 
Hey Pavel, welcome. If you put your general location in your profile, there will most likely be someone in your area who could help.
 
Guys, thank you for your recommendations - I have already know. I know the procedures, risks, technology... I have all equimpment for work with presure...

Yes, I need to speed up the soak cycle -> pressure. I only don't know what pressure would be optimal. that's all. Any ideas? :)
 
Based on Your name I wanted to recommend knife.cz forum but as I see You already logged there. :)
 
PavelKa said:
Guys, thank you for your recommendations - I have already know. I know the procedures, risks, technology... I have all equimpment for work with presure...

Yes, I need to speed up the soak cycle -> pressure. I only don't know what pressure would be optimal. that's all. Any ideas? :)
Click to expand...
So you have a vacuum setup as well correct? As I stated above, no amount of pressure will work for stabilizing. It can only help to shorten the soak time. As for pressure needed, it would depend on the wood species. The only way to know would be to do some testing.
 
Kevin,
That summarization is mostly correct, but the notion that pressure can't make penetration deeper would only apply if wood was completely dense like steel and if the liquid it was in was to remain in the same state. Wood, however has voids,tubercles and other ways that air and vapors can be moved through it. The liquid resin is uncompressible, so it drives into the wood harder than the trapped air … which will become much smaller in volume under high pressure, and move into deeper the wood fibers or dissolve in the liquid. Since the resin is catalyzing under the pressure, any pressurized trapped air or other gasses will remain trapped, thus making the pressurized wood somewhat more dense than wood done only by vacuum because more resin was in the wood. Upon the resin being catalyzed after the release of the pressure, some of the bremaining gasses will escape through open pores, tubercles, and directly through the wood. The rest will remain trapped permanently where it is in the resin matrix.
The additional resin penetration compared to vacuum only isn't a night and day thing, but it is one reason why pressurized curing is better.
 
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That is why Cactus Juice works so well for stabilizing, but ONLY for open pore woods, not dense small pore wood like Black Walnut. With maple woods you will get 100% penetration with vacuum, but do have to pull vacuum for 2 to 4 hrs, then let wood sit in resin for 8 to 12 hrs, and overnight is best. What seems to work pretty good is to start process pulling vacuum today, perhaps right after noon, run vacuum for 2 to 4 hrs, then let soak in resin until next morning.

Pressure won't do anything for the result from that since there is full 100% penetration anyway. The finished block of wood will sink in water, or at most float level with water, just like the stabilized blocks from K&G.

On pressure it seems like I remember reading somewhere K&G used up close to 1000 PSI (maybe more?) pressure? This is what makes it possible to stabilize woods like Black Walnut to get 100% penetration. Vacuum sure won't do it.

Ken H>
 
Kevin McGovern said:
It can help to shorten the soak time. As for pressure needed, it would depend on the wood species. The only way to know would be to do some testing.
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I agree with you all guys. I just want to speed up the soak time. Problem is that I have to buy pressure chamber at first. And that is why I need to know what pressure works good before I will choose the chamber, I can't do any testing :D one option is to buy some pressure pot (only 70PSI) or the second one build my own chamber (approximately 150PSI maybe more)
...K&G uses very high pressure, I know... But I also heard that it can be done under pressure 150PSI.... -> it takes much longer.....

Stacy E. Apelt - Bladesmith said:
Wood, however has voids,tubercles and other ways that air and vapors can be moved through it. The liquid resin is uncompressible, so it drives into the wood harder than the trapped air … which will become much smaller in volume under high pressure, and move into deeper the wood fibers or dissolve in the liquid.
Click to expand...

I also heard that very high pressure can damage voids,tubercles,fibers etc. in wood - it is too fast and so wood does not have enough time to suck the resin properly - when you take it of the resin, big portion of resin get out. pressure 150PSI takes much longer but it could be an option. But I really don't know if that's true... any idea?

sorry for my english :) thank you!
 
You
Stacy E. Apelt - Bladesmith said:
Kevin,
That summarization is mostly correct, but the notion that pressure can't make penetration deeper would only apply if wood was completely dense like steel and if the liquid it was in was to remain in the same state. Wood, however has voids,tubercles and other ways that air and vapors can be moved through it. The liquid resin is uncompressible, so it drives into the wood harder than the trapped air … which will become much smaller in volume under high pressure, and move into deeper the wood fibers or dissolve in the liquid. Since the resin is catalyzing under the pressure, any pressurized trapped air or other gasses will remain trapped, thus making the pressurized wood somewhat more dense than wood done only by vacuum because more resin was in the wood. Upon the resin being catalyzed and the subsequent release of the pressure, some of the pressurized gasses will escape through open pores, tubercles, and directly through the wood. The rest will remain trapped permanently where it is in the resin matrix.
The additional resin penetration compared to vacuum only isn't a night and day thing, but it is one reason why pressurized curing is better.
Click to expand...
You are assuming you would catalyze while under pressure. I'm not sure how one would accomplish that. If you have the wood submerged while under pressure, you can't cure it that way, unless you want your entire vessel cured. If you remove it from the pressure vessel to cure, the compressed air in the block would push out any resin added via pressure. At least I can't figure out a way this could be done. Not saying it can't.
 
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The instructions from TurnTex state:

“If you have the equipment, you can also add a pressure cycle to speed up penetration. Adding pressure is not necessary for complete penetration, it just slightly speeds up the natural equalization process you can get by just allowing the blanks to soak.”

As to the pressure being needed for certain woods, the instructions also seem to indicate that is again more a matter of timing rather than requirement:

“Some species of wood such as Walnut and Redwood benefit from an extended soak. I usually soak these for 1 week.”

Based on that, what Kevin says would seem to make sense. If you are stabilizing as a business you sure as shoot aren’t waiting a week. I won’t quote the entire instructions as folks can go to their site and read them, but one of the key things is the wood being very dry. I would guess this is one of the steps most often skipped by home stabilizers that results in the biggest difference. I assume the professionals put everything in a kiln and dry it out real good first. There is also a tip to avoid oily Woods because the oil can get into the resin and ruin it.
 
Kenin.
You are correct, I meant polymerizing. The catylizing is done by heat after the blocks are taken out of the chamber and the excwess is dripped off. From what I understand, the pressure cycle drives the resin deeper into the wood and the resin starts forming the basic polymer chains.
 
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