Vacuum stabilization experiment - LONG
Brian Roberts
>Wondering if anyone has tried vacuum methods for stabilizing wood?
After checking out Max Krimmel's alabaster turning site (beautiful work!), I decided to try his method. He uses a dilution of Weldbond glue (1 part glue to 3 parts water) and a homemade vacuum chamber to reinforce some of his alabaster pieces at various stages of the turning process.
I had a VERY well spalted, with many soft, punky areas, piece of maple that I was attempting to turn into a vase. Nothing was working to prevent tearout. The piece was basically beyond hope.
I built a chamber out of plywood (overlapped at the corners - kind of a box within a box). I had a piece of acrylic about a foot square and an inch thick (the top of an old iron end table - I knew I kept it for a reason!) - so the "inner box" was left shallower by about 7/8" so the acrylic would sit about 3/16" proud of the "outer box", after placing some 1/4" closed cell weather stripping material on the edge of the "inner box". This allows me to get a grip on the acrylic to remove it (did not want to alter it in any way, thinking it would be weakened).
Not sure how clear that was - I have a box that is 1 1/2" thick on four sides and the bottom - with a stepped opening on the top to accept the drop in piece of acrylic. I suppose other materials would work for the lid, but the acrylic allows me to see what's happening in the chamber. As it turned out, this became very useful!
I drilled a hole through the box and epoxied in a barbed hose fitting (attached to a pipe nipple to provide full glue surface through the box side).
The first test I was only able to pull about 10 inches of vacuum - plywood allows an amazing amount of air to flow through it! Applied two coats of epoxy paint inside and out. Second test pulled 20 inches of vacuum, but started to see little epoxy paint bubbles forming everywhere on the inside of the box as the vacuum pulled air through the wood! One day dry time was obviously insufficient. Let it dry for a week, put on one more liberal coat, another week to dry and test number three....... holding my breath... 25 inches of vacuum!! At that vacuum the 1" acrylic bows in about 1/32" - should be okay.
As a first experiment I put the wasted vase in a plastic bowl filled with the Weldbond solution and turned on the vacuum pump. Good thing I could see through the top - instant foam from the bubbles coming out of the wood. I left the pump on until the foam was nearly overflowing the plastic bowl - shut it off until the foam went down - pump on again - it took about ten cycles before I could finally leave it on without foaming over - left it under constant vacuum for about ten minutes - pulled it out - wiped off the excess and set it aside to dry overnight.
The results look very promising. The areas that I could have pushed a finger through are stabile, though somewhat flexible - though, since very thin, they would be flexible anyway. I can't remount this piece to try sanding on the lathe, but hand sanding and RO sanding seem to work allright. I suspect the fact that this is diluted glue may cause some problems with high speed sanding - time will tell.
I am looking forward to trying the process on a piece BEFORE it is beyond salvaging!
Any ideas for a stabilizing solution that would dry (or cure) harder than the Weldbond? Can epoxy be thinned enough, with something, to enable good penetration into the wood? I have read (here and other sites) about Paraloid B72 (used for restoration stabilization), but have no idea what it's consistency is, or how hard it dries.
I have used CA, in limited applications, for stabilization, but would like to arrive at a process for more complete impregnation that I can do in shop.
Any ideas or suggestions very much appreciated!
Thanks - Brian
