help a beginner measure mc in wood with confidence

[Gene Nelson]

Gene - I've dried down and weighed more blocks of wood than I care to admit. I never was able to get consistent results. IMHO, it may be difficult to do oven drying with a softwood like spruce because a lot of volatile organic compounds are outgassed during the drying process along with the water and I think that tends to skew the results......  Anyway, I gave up on that a long time ago.

<I think you are correct and I was suspicious about the dried block - it will never take up moisture like the un-dried blocks so even at 190 deg f for 24 hrs something damaging must be happening to the wood.

  Table 3-4, "Moisture content of wood in equilibrium with stated temperature and relative humidity", in the USDA Wood Handbook is a table that lists temperature dependant wood moisture contents (MC) at various relative humidity (RH) values - i.e. wood that has come into equilibrium with an environment at a certain temperature and RH will have a certain MC.

  < I have it.

  So you don't have to measure MC directly (wood moisture meters do not work reliably at MC of about 6% and below - so don't bother buying a moisture meter). All you need to do is to monitor your hot box environment for temperature and RH. I suppose a cheap RH meter is okay, but I bought a good one - about $200 - and comes with a certificate of calibration to some fancy-dancy standard. So now you have your temperature and RH known, now all you need to do is to determine whether the panel has equilibrated with the hot box environment. There are a number of ways to do this, I use a direct and very simple method - it's got a complex name - don't let it scare you  - ready? - "Direct 
  Linear Measurement" - i.e., put a tape measure across the panel and measure it.

  < Do you have the sling hygrometer? What brand and where did you get ?
  I suppose that after the board is ribbed, this same movement can be measured as available crown with similar associations with changing environment?

  Thanks Terry,
  Gene
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