Vacuum Chamber?

Discussion in 'Woodturning Discussion Forum' started by Tom Albrecht, Dec 3, 2017.

  1. Hy Tran

    Hy Tran

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    Tom--to answer the question about what kind of stabilizing resins other than "cactus juice":

    There are basically three types of chemistries of polymers commonly used to stabilize wood: Polyester resins, epoxy resins, and polyurethane resins. The characteristics that you want are low viscosity and good wetting when uncured, and good mechanical properties (shrinkage, hardness, & machineability) when cured. I believe that cactus juice is a polyurethane, but don't quote me. For cosmetic (or I suppose artistic) reasons, you probably also care about color and transparency, depending on your wishes and needs. Cactus juice cures mostly clear (it may be slightly amber in large thicknesses); it requires heat to cure.

    Craft casting resins are both epoxy and polyesters (or polyurethanes), depending on the source. Hobby Lobby and Michaels both have two-part clear casting resins, that are fairly liquid in the uncured state (similar viscosity to maple syrup?); cure at room temperature in about 24 hrs. I have a pint-container of casting resin (epoxy, I think) from Hobby Lobby that can be dyed, and after curing, it's actually machineable.

    Another casting resin that's probably more difficult to get, and has more hazards at the consumer level, is acrylic monomer. Acrylic monomer is often used by dentists, and cures at room temperature.

    In terms of consumer safety, in my opinion, in the uncured state, 2-part polyurethanes and epoxies are safest (low volatile content); polyesters are less safe (the polymerizing agent is typically a highly flammable liquid); acrylic monomers are the least safe (monomer is quite volatile). In the uncured state, be sure to use protective equipment to prevent contact with skin or other external organs (or internal organs). Cured (or more correct technically: Polymerized or cross-linked), the resins are all inert and relatively safe, and are safe to the touch.

    Google (or other search engine) can be your friend: use "casting polyurethane resin" and look at the data sheets. For reference, water viscosity is about 1 cps (centipoise); light motor oil is about 100 cps, light syrup is about 1000 cps. For hardness, you want the resin to cure to a hardness quoted on the "Shore D" scale, the higher the number, the better. If they quote "Shore A" scale, the cured polymer is likely to be more rubbery, and will not machine well.
     
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  2. Tom Albrecht

    Tom Albrecht

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    I just recently corresponded with Curtis from Turn Tex about this. When I asked about stabilizing rough turned bowl blanks, he suggested just submerging them in juice and soaking for a week or two, with no vacuum.
     
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  3. Glenn Lefley

    Glenn Lefley

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    I personally could never wait that long, but it will certainly work. Dry wood placed in liquid will soak it up eventually back to 35 % moisture content , I would think.
     
  4. olaf Vogel

    olaf Vogel

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    I use epoxy resin, thinned with alcohol. It penetrates deep enough for me, which is usually less than 1/2”

    For a chamber, I use an old Binks paint pot. A factory was selling them cheap, used. One came with a lexan lid like this https://www.google.ca/search?q=bink...AUIEigC&biw=1024&bih=653#imgrc=mrx2YBS36jETWM:
     

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