I tried epoxy filling a wood blank that is severely cracked and the test produced a completed vase. The piece is spalted pecan and was in the scrap pile due to the condition of the piece.
The steps documented with pictures are as follows:
Examine the target wood to ID problem spots
Seal the blank with Tuck Tape leaving one end open - my case this is the worst end
Mix epoxy and color if desired
Place the sealed blank on a disposable paper plate and fill epoxy into open end
Fill to above the material to account for voids in the material
Place material and the paper plate in the pressure pot and close all four clamps to seal the pot
Connect shop air to the pot and open the fill valve charging to 50psi
Close the fill valve and disconnect shop air
Carefully move the pot to a safe location under the large lathe or glue up table
Let sit undisturbed for a full 24 hours then release pressure and open the pot
The main choice between vacuum or pressure is what you are trying to fix in the material. If you have cracks or large voids then pressure is your friend as it forces the resin into voids and any trapped air compresses to a tiny bubble or escapes through the top as shown in the one picture after five minutes or pressure. If you have punky or spongy wood without major voids you use vacuum followed by heat in an oven if available for a full cure. The tiny air pockets escape allowing the resin to flow into and diffuse into the wood. With vacuum you use a resin that is close to water in viscosity and needs either heat or a long setup time to fully cure.
There is a debate going on if you can use a pressure pot (designed for up to 50psi or approx 3.45bar) as a vacuum pot as well. Some are reporting mixed results and most manufacturers do not recommend trying a vacuum with a pressure pot. My current experiment in the pressure pot is a piece that is punky and has voids.
David,
I’m enjoying this discussion and do not have any experience with it. I’ve heard several makers using “cactus juice” or something equivalent to resin impregnate wood that is then used as pen or marking knife handles, turned into carving mallets, and even hand plane and saw handles.
Is this essentially what you did with the spalted wood blank? Does it produce the same result but with a different process?
Thank you, Michael
I’m not surprised that vacuum is not recommended. Keeping air in and the pot from exploding is quite a different task from keeping air out and the pot from imploding.
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“[In a spaceship diving underwater:] ‘How many atmospheres can this ship withstand?’
‘Well it’s a spaceship, so I’d say anywhere between zero and one.’” — from Futurama
Stabilization under vacuum is different as it requires vacuum followed by a heat treatment that cures or sets the resin. A great reference is HERE and comes from the folks at Cactus Juice. One important thing to note is they recommend the moisture content is 0%. Once you stabilize something it has a different feel - almost waxy but not slick.
The spalted blank had some slightly soft spots but my main concern is filling the cracks as that is something the vacuum process does not adequately address. I have a bowl blank that is up next that has a few voids but is more soft making for a good experiment.
