Kitchen Knives Set – Part 5: “Fun” with Resin

Somebody somewhere in the comment section (I think on Marcus’s blog) expressed dislike for resin stabilized wood along the lines that it is the same as making the handles out of plastic. I disagree. Stabilized wood is a pain to work because it behaves like plastic in that regard, but it does not look like plastic and neither does it feel like plastic in the hand – it feels like wood. And as I was working on this project, I found out that it even sounds like wood – stabilized pieces give out very nice clonk-clonk when hit against each other. I think it might be possible to make musical instruments out of it, but I won’t try.

However, before said wood reaches its desired stabilized state, I have to work with epoxy resin. Lots of it.

I hate it.

It is gluey, it sticks to absolutely everything and it is transparent, so when it drops somewhere it is difficult to see in time. Tools and surfaces need to be cleaned with paper towels soaked in denatured alcohol, which is not cheap and the fumes do not smell exactly delicious. And the work needs to be done fast, because if the epoxy gels, it won’t soak into the wood no more.

With my macgyered vacuum pump I have reached a vacuum of 0,2-0,3 bar, which was sufficient for extremely porous wood, but might not be sufficient for this. Applewood has very small pores and is very hard, even the very decomposed pieces were still harder than for example poplar or basswood. So I have decided to bite the bullet and buy a small, cheap vacuum pump in the hope that it will work better. And it does – and it does not.

© Charly, all rights reserved. Click for full size.

Even with my poorly sealed pickle jar, I have easily reached vacuum 0,6 bar within a minute. The wood released so many bubbles that the resin developed foam head like beer.

However, the pump also got very hot after a few minutes of running, which made me a bit worried. My macgyvered pump was a bit cumbersome and awkward, but overheating was completely a non-issue. I am not so sure about this one. I hope it does not burn out before I at least get to sell some knives.

© Charly, all rights reserved. Click for full size.

Overheating aside, the wood soaked up the resin very nicely and although I have only used clear resin, it developed very nice and pleasant colors. The resin would cure over time at room temperature, but it is possible to speed up the curing by heating it to 60-80°C. So I did that the next day and I baked the pieces for two hours, after which I could appreciate the nice clonk-clonk that I was talking about at the beginning.

I have also approached the issue a bit more scientifically this time and I have weighed all the pieces before and after. Here you can see the results.

© Charly, all rights reserved. Click for full size

This made me very happy with the results. The relatively healthy wood has gained approx 30% in weight, the not-very-much rotten root wood doubled its weight and the more decomposed wood has almost tripled its weight. All pieces of similar size weighed approximately the same after the stabilizing process, irrespective of what wood they were made of. And finally, all pieces when put in water either sunk completely or just barely floated with 99% submerged. So even the relatively healthy wood should be soaked up with resin to sufficient depth.

Now that the wood is stabilized, the only thing that is left is to psych myself up to go into the freezing workshop and finish the knives. Which includes first a bit of grinding and drilling, and then a lot of gluing. Even more fun with epoxy awaits, hooray!


  1. says

    Is it a rotational pump or a membrane pump? If it’s a membrane pump don’t keep the vacuum on the pump -- use a valve to keep the vacuum in the chamber and drop the pressure on the pump. With a rotary pump if it gets hot that may indicate a shortage of oil, which serves as seal and coolant.

  2. says

    Also: is that a glass jar? If so, that is terrifying. I use a stainless canning pot with a big lucite lid and a silicone (made from a silpat) gasket. I have everything that might implode or shatter taped with strapping tape to keep it from turning to shrapnel.

    For odd shaped items I put them in a ziploc bag and squeeze the visible air out. When it’s vacuumed the bag expands but the resin has nowhere to go but into the wood. There are silicone bags also for this purpose.

    Some brands of resin can be thinned with denatured alcohol so they penetrate better. I use a stuff called cactus juice which is water density and cleans up with windex or soapy water. Cactus juice is cheap-ish compared to West System or whatever.

  3. dangerousbeans says

    in my (limited) experience it does feel different to un-sabilised wood. but it does allow you to use spaled, pucky, or other wood that would be unsuitable to make a handle, so it is a necessary step if you want to use those woods in a handle.
    those look like they will make very nice handles

  4. says

    You won’t hear me criticise the use of resin. I also thinks it really pops the grain. So pretty.
    Vaccum pot is the next thing I’ll get, but only when it#s warm again…

  5. says

    @Marcus, it is probably a rotational pump, since the specs say “oil-free”. The specs unfortunately do not say how long it is safe to run the thing. The part that heats up is the motor.
    The jar is glass, but it is thick-walled and is designed to be vacuum-resistant. Nevertheless, I have first tested whether it holds up to the vacuum by wrapping it in a blanket, and even though it held up, I have worn protective glasses during the work just in case. I do try to hold the vacuum via the ball valves, but unfortunately, I was unable to seal my setup well enough so once the pump is turned off, the jar quickly starts to gain pressure again. I have my eyes on a stainless vacuum chamber for a mere 100,-€ and I think I will go for it for the next project. 100,-€ is not exactly cheap, but I think it is worth it to replace my current mcgyvered jar. I would love to have a pressure chamber too, but those cost 1.000,-€ and thus are currently way out of my reach.

    @dangerousbeans it does feel different to un-stabilized wood, that is true. But wood treated with linseed oil or beeswax or lacquer also feels different from untreated wood. In fact, in my (also limited) experience a handle infused with resin feels similar to a handle infused with tung oil or linseed oil.

    @Giliell, I think that vacuum pot and small vacuum pump would be worth it for you too, they do make the work so much easier.

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