Resin infusing wood (“stabilizing”) is all the rage in some parts of the knife-maker community. I used to impregnate all my handles with linseed oil and slowly dry them – same effect, just a different polymer.
Here’s how it’s done: basically, you need something to hold the wood under the resin, a container, and a vacuum pump. I have a vacuum chamber that I made for degassing my silicone molds (turns out they generally don’t need it!) consisting of a lucite panel and a silicone gasket, that goes atop a 2 gallon stainless steel pasta cooker. The panel is drilled with a T, and a ball valve (to release the vacuum) and a hose with a quick connect to the vacuum pump.
Initially that was how I did my resin infusion but I got resin all over the place because the container I was using inside the cooker was silicone and would flop around. Mike P. got one of of the Conestoga systems, which I had been, seriously, thinking of building myself, but given that the Conestoga system cost about $10 more than the parts, I got lazy.
The upper lid is routed in a circle and poured with silicone to make a gasket. Very nice! There’s a sort of dipper-thing which is also convenient as heck: you can lift the wood and let it drain by clipping it with a clamp across the upper rod. The lower and upper parts are heavy steel, which prevent the wood from floating up. You put your wood between the steel parts, adjust the set-screw, and lower the whole mass into the cylinder. Then, you pour the resin in, pop the lid on, and evacuate the tube.
Cactus Juice is the commercial name of the resin I use; it’s popular and is compatible with most alumilite dyes. So some knife-makers infuse UV colors into perfectly good wood, or add a ton of black for that Tactical(tm) appearance. I admit that I have 2 gallons of cactus juice resin – one clear, one blue/black. The blue puts lovely hints into bog oak, and the resin really strengthens some otherwise crumbly wood. You can resin infuse spalted wood, as I have on some of my knives, and it makes it solid enough to use for knife handles.
I usually do several cycles of bringing up the vacuum, letting it sit (there is a slow leak) and infuse, then bringing the vacuum back up again. After a while the wood will hardly bubble at all. That’s when it’s done.
Here’s what it looks like:
I’m not a material scientist but my understanding of how most epoxies work is that they are thermal cure, and the “hardener” is a catalyst that warms the epoxy up, cooking it to a cure which makes it harden and expand slightly. The Cactus Juice appears to be a resin with thinner and no hardener – it’s like thick water, odorless and cleans up with soap – but you can cook it and it gets hard. Once I’ve infused it, I wrap it in parchment paper so it won’t weep resin and stick to something in my oven, and leave it to cook for 2-3 hours at 220F.
Other knife-makers use aluminum foil, which sticks like mad to the resin; I keep telling them to try parchment paper. I get a lot of “thank you” emails.
After 3 hours it looks like this:
You can see where the resin foamed out and hardened. That would have glued the wood pretty thoroughly to anything that is not seriously non-stick. The resin sands and shapes as though it’s not there and gives the wood a bit of extra gloss when you finish and polish it. What’s really nice is that it does not completely seal the wood, so normal finishes like wax and oil will penetrate a little way in and you can’t tell the wood is sealed inside.
The people who make Cactus Juice are smart – they put some mild scent in the resin, so you can tell it’s cooking but it’s not too nauseating.
This technique is inexpensive and valuable. I may use it for other wood projects and possibly even leather. In my wood shop area, I have a wood lathe that I have been meaning to set up, so I can do some composite wood/resin bowls and stuff like that. I’ve just been too busy with the metal-work (though the lathe would help for doing handles!) I may try doing some spalted wood bowls – basically, rotten wood – after resin infusing them. I wonder if they’ll survive turning? I’ll wear a leather coat and my face helmet if I try that.
I’ve got the vacuum pump on a separate base with a power switch and suction feet. That makes it incredibly quiet for a vacuum pump. I used to use this unit to vacuum filter my silver nitrate for wet plate photography. Having it rigged with a quick release is very useful.