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44K views 22 replies 10 participants last post by  Gluroo 
#1 ·
Creating a vacuum container

The thermoplastic handle scales on my folk's Wüstof knife broke, and I thought I'd replace it with some wood scales. I had some offcuts of claro walnut that were the right size, but I wanted to make sure that the new walnut scales would hold up to kitchen use.

I did a little research in some knife-making web sites and forums and learned a bit about wood stabilization, where you impregnate wood with some material (epoxy, resin, etc.) to harden it and make it more durable. Some home knife makers just soak the wood in polyurethane, but the better method is apparently to put the wood in a container with the poly and put it under pressure by using a vacuum pump. This pulls the air out of the wood and allows the poly to fully absorb into the wood. This same technique could be used on pen blanks or other small pieces of wood that need to be stabilized (punky spalted turning blanks, maybe?)

We have a hand wine vacuum pump to take out the oxygen so you can preserve opened bottles for a few days. The same pump and nozzles are used for doing vacuum bag lamination in woodworking, so I figured it would add enough pressure for this project. I ordered an extra pack of nozzles, took a tall canning jar, and cut a hole for the nozzle in one of the tops using a spade bit in my egg beater drill.


I originally thought I would have to seal the sides around the hole with caulk, but a test with an empty jar showed that the nozzle was holding pressure on its own.

I put the walnut scale blanks in the canning jar, then filled it with a bottle of Minwax Wood Hardener (which is just poly with a bunch of solvent, apparently) and some Minwax wipe-on poly thinned with mineral spirits. I had to leave enough air space for the end of the nozzle, so the blank ended up being not completely submerged. Then I used the pump to create the vacuum pressure. Small air bubbles immediately started coming out the wood.


Now I get to wait and let it absorb under pressure.
 
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#4 ·
Supposedly the hand pump will put out around 20 inches of pressure. It was certainly enough to pull the air from the blank, as evidenced by the air bubbles. I'll pull the blanks from the jar when the scales sink down.

I forgot to take a picture of the blanks before, but here's a picture of a different part of the same board the blanks came from:


This pic gives a yellow cast to the wood that isn't present. It's much more uniformly brown. But you can see the figure even rough-sawn.
 
#5 ·
That's purtyful! I'm sure they will come out nice.

I was raised in a family with a lot of professional cooks. Knives were a passion for my mother and my grandmother, aunts and sisters. Most of the time, (up until the early 1970's), they would treat the knife handles the same as the butcher block in the restaurant…....... Beeswax and mineral oil mix.
 
#7 ·
I use beeswax and mineral oil on my wooden cutting boards and wood handled knives, too. Works great.

My parents are are relatively hard on their knives, so I think the knife scales need a little extra protection.
 
#8 ·
Beeswax is nice and the mineral oil probably penetrates a lot better than what I use. My only objection to beeswax is that it doesn't much like water and I'm always washing the handles in detergent, but not in the dishwasher.
 
#9 ·
Stefang, Beeswax is antibacterial and antimicrobial and doesn't come off in water. With any wood utensil it should never be soaked in water.

When we do dishes, and when I grew up, knives and wooden spoons or spatulas were never left in water.

Dipping the knife or utensil in dishwater won't hurt it, letting it sit for minutes will.

Being antibacterial and antimicrobial, Beeswax adds to the ability of the wood to destroy any bacteria or microbes.

Edit: Sunflower oil will eventually turn rancid. Mineral oil, Beeswax and I believe grape seed oil does not. There may be others that I've forgotten.
 
#10 ·
And that is where the problem comes in Ian. I have used Beeswax for many years on turned bowls and stuff and it has held up extremely well as long as the bowls weren't used for fruit or other moist items, but any constant or residual moisture does have an effect. And yes, I am guilty of letting the knives sit in the dishwater. Maybe true that sunflower oil will turn rancid, but I'm sure mine never stays on long enough for that to happen! I have to say though that I am not convinced that oil preserves wood at all. I think it just makes it look better. You may know a lot more about that than I do. What do you think? Outdoors it certainly can make a difference if it contains some resins, otherwise it just evaporates away and the wood goes about it's natural business.
 
#14 ·
I don't want to nit-pick and be botherson but I'd like to get a clarification on your process. You sometimes say vacuum and other times you say pressure. Those are to different situations. You mention using vacuum and seeing the air bubbles coming out of the wood, Then in other places you refer to pressure.

I've read other articles and they use vacuum to get all of the air out of the wood and then you follow up with pressure to try and force the liquid into the wood.

If you were making pen blanks with a colored stabilizer you'd want it to get all the way to the middle of the blank.

So my question is did you just use vacuum or did you follow that up with a pressure pump?
 
#15 ·
Sorry for the imprecision. You can read them both as "vacuum pressure." Lowering the pressure in the jar by using the vacuum pump pulls the air out of the wood, allowing liquid to penetrate the wood.
 
#16 ·
"I don't want to nit-pick and be botherson but I'd like to get a clarification on your process. You sometimes say vacuum and other times you say pressure. Those are to different situations. You mention using vacuum and seeing the air bubbles coming out of the wood, Then in other places you refer to pressure."

I was thinking the exact same thing. I work in the refrigeration industry and routinely use mechanical pumps to pull systems into a vacuum state. Never heard of it being expressed in terms of pressure, I am accustomed to it being expressed in inches of Mercury and/or microns….So I was rather confused myself.
 
#17 ·
Great idea? why mix the wood hardener and Poly? If you can figure out how to do this on a larger scale you could make mallets, and chisel handles out of softer figured woods a la Blue Spruce!
 
#19 ·
Results from overnight



The scales were on the bottom of the jar, and no more air bubbles were released after adding some more pressure, so I took out the scales to dry. They're noticeably heavier.



You can either replace the lid with a new one, or just re-pressurize the jar to store the stabilizer.
 
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