How long does plywood need to dry before using?

Discussion in 'Materials' started by 67-LS1, Feb 13, 2023.

  1. 67-LS1
    Joined: Aug 2003
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    Location: San Francisco Bay Area

    67-LS1 Senior Member

    I’m definitely using epoxy. The West System seems to be the simplest and most thorough system for a newbie like me.
    I'm also going to fair everything out to make sure I don’t have even a pinhole.
     
  2. wet feet
    Joined: Nov 2004
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    Location: East Anglia,England

    wet feet Senior Member

    I've never had too much faith in moisture meters.They work well in the zone between the probes,but I have grave doubts about the moisture content of anything being absolutely uniform throughout.Immediately after coming out of a kiln is probably the best time to get a good result.My own experience of sheet materials includes MDF left in a cold and humid boatyard shed.It swelled in thickness about 8% at the edges of the board and moisture was the cause and yet the middle of the sheet,which was covered by the rest of the stack retained it's original thickness.Which illustrates that exposed surfaces are likely to contain more moisture.so where do you apply the probe to get a realistic reading?I do know of a few workshops where a daily record of humidity is maintained and it is a handy record to have.

    A more reliable method is to weigh a sample,and good digital scales are not only cheap but they are virtually essential for mixing some formulations, and then heating it in a well controlled oven to about 105-110 deg C to remove all moisture.When the weight has stopped going down you weigh it again and do the calculation.It can be really easy if your small oven has a modern digital controller.The result is beyond doubt.
     

  3. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    Have faith. Wood takes a long time to dry. About a year or use of temperature controlled kiln. It is the innermost fiber that takes a long time to dry. Once it dries, the reverse takes place. It is the outermost fibers that quickly takes in moisture while the innermost remains dry. I suppose when the manufacturer bonded the veneers, the wood is dry in accordance with the specs.

    According to the instruction manual, only the surface and edge can be measured nu the meter. I guess to measure inside humidity, you have to prick it.
     
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