Using vacuum to treat punky wood??

Re: Using vacuum to treat punky wood??

David Walser

Barry -- With the proper equipment, it's possible to use vacuum with volatile chemicals. I'm not sure if your proposed method would work. The idea of using a vacuum chamber is to suck as much air out of the wood as possible -- while the blank is submerged in the stabilizing resin. When the vacuum is released, the space that had been taken up by air is (hopefully) replaced by the resin. With your method, once the vacuum is released and the valve to the resin chamber is opened, a lot of air will rush back into the vacuum chamber (and into the blank) -- preventing the resin from fully penetrating into the blank. At least, I think that's what would happen.

But let's assume that it did work. The question is, unless you had to use those volatile solvent-based resins, why would you bother? There are non-volatile stabilizing resins (such as Cactus Juice) that work better than something like Minwax Wood Hardener. By weight, most of the solvent-based resins evaporate, leaving precious little that actually strengthens the wood. In contrast, about 99% (by weight) of the non-solvent based resins cure into a hard plastic that forms a solid matrix with the wood fibers. In addition, these non-volatile resins are usually non-toxic and inflammable and are cheaper.

Note: I don't have a dog in this hunt. I don't have a financial interest in Cactus Juice or any other resin. I occasionally use Minwax Wood Hardener -- but only one relatively small areas. More frequently, I use CA glue -- on even smaller areas or where just the surface needs to be stabilized. If I want to treat an entire blank (from pen blank on up in size), Cactus Juice is, for me, the way to go.

Re: Using vacuum to treat punky wood??

Ken Vaughan

Barry

Unfortunatly, the rules of chemistry and physics plot against such an approach.

Light solvents like acetone boil easily as the pressure decreases, and the gas form occupies many times the space of the liquid form without getting into pressure . I do not have my old Handbook of Chemistry and Physics handy, but they be looked up. Passing the vapors through the pump is an alternative to very large containers.

Vacuum pumps that handle petroleum solvents are available. They and the explosion proof electrical work get beyond practical pretty fast.

Urethane formulations such as cactus juice avoid the fire/explosion risks but they do not like moisture, and work best with high vacuum levels (about 29 inches mercury).

Vacuum bags are available from vendors such as Packard Woodworking for vacuum stabalization with urethane formulations. And the item needs to be heated to an internal temperature of at least 185 degrees F.

Re: Using vacuum to treat punky wood??

Keith Newton

Barry, another option may be to place the object in a bag which has two tubes, one for pulling the vacuum, the other to supply the liquid after the other has been closed.

So you probably know, pulling a vacuum isn't like pumping fluids where the pump just moves a given volume then, bam your done. Instead, the air inside a chamber gets stretch, the stretch some more getting thinner and thinner until there is nothing left. I suppose this is easier in an empty vessel, yet harder when the vessel is solid wood where the air inside each cell has to pass through a lot of cell walls to get out of the core.

If after the pump has run long enough to pull as good a vacuum as it can all the way to the core, the vac hose could be closed, then the other opened, with it submerged in your chosen fluid hardner. Let the internal vacuum pull your hardner in without the risk of pulling the vacuum while its submerged.

Re: Using vacuum to treat punky wood??

mikeee12345

Another option when using a bag and vacuum is to run the vacuum hose through

a secondary vacuum enclosure that prevents the possibility of pulling liquids into

your vacuum pump. You can also run the vacuum through a paper filter that keeps

contaminates from pulling through to the vacuum pump. The most common method

for cactus juice resin is to use a vacuum enclosure large enough to hold the wood item.

The item is secured or weighted down in the enclosure and cactus juice is added until it

covers the wood item. The vacuum is applied to the enclosure until you start seeing air

bubbles release from the wood item. You slowly increase the vacuum to reduce the chance

of the cactus juice boiling over in the chamber from the air bubble activity and pulling liquid

into your vacuum line. You can close off the valve to the chamber and shut off the vacuum

pump and monitor the vacuum on the chamber. When the vacuum drops you can start the

pump, open the valve and pull a vacuum until you start to see the bubbles again. When you

stop seeing bubbles in the liquid, your wood is usually saturated. Remove the wood item wrap

it in aluminum foil and cure it in an oven at a low temperature.