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RH issues?

Started by SoftWood, October 05, 2018, 02:15:12 AM

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YellowHammer

The key is to set the EMC conditions at a minimum acceptable level so the wood can't get below that.  All the wood in the system will converge to but not go under that level, it won't just keep drying out more and more. It's an EMCSN (EMC Safety Net) and will keep from overdying the wood even if all the boards start at different levels.  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

SoftWood

Thank you for the continual help Gene & YellowHammer! 
It's making sense what you're saying & im aiming for that now but I am getting defeated.
I'm getting close, RH wise, to start checking lumber to see where I'm at & did so today & im pretty far off from what the ecm charts say I should be at. 
I have a hygrometer/temp gauge in the kiln that records the min & max.
My temp is constant between 102-104 & RH is down to 41-44 last night/today, it dropped a few percent each of the last couple days. I havnt bothered checking the wood since the first week because I figured I am so far off still, but when I probed the wood today, 3/4 of it is showing %6, as low as my meter goes. But by the charts I should only be in the mid 7's.
Had planned to try & keep it around %35 RH in there until all lumber showed the same MC. 


GeneWengert-WoodDoc

How are you measuring MC...Equipment brand name?  If needle type, are they insulated and how deep?  Species or temperature corrections? 
Do you measure humidity with a wet-bulb and have good air flow on the bulb?
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SoftWood

It's a Lignomat mini E/D meter with 3/16 pins, I don't think they are insulated.  I used a dry bulb, species is western red cedar. 

YellowHammer

One of the most useful skills you can learn is how to oven dry wood to measure true moisture content. It sounds a little intimidating, but is very easy, and with an accurate food or better scale, will tell you exactly what your wood is at, if your meter is reading incorrectly, and will give you a gold standard approach to measurements.  Ironically, once you have a sample specimen in the kiln, it takes aout the same effort to put it on a scale and calculate the result as it does to hammer pins in.  Well... not quite as fast, ;D  but certainly more accurate. 

 
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

GeneWengert-WoodDoc

With this meter, you are getting mainly the surface MC.  The core is likely wetter, so the average MC of the piece is likely higher than 6% MC.

Even so, at 45% RH at room temperature, we would expect to see around 8% MC.  The temperature correction, using the temperature where the needles are driven, is about 1% MC for every 20 F hotter than room temperature.  Add when colder and subtract when hotter.  So, in your case, either the meter is wrong or your humidity is wrong.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SoftWood

The gf isn't convinced that it'll be fine to oven test the wood, but I'm working on her.

I did get the moisture meter somewhat sorted. Got some longer pins, 7/16", & now its showing a higher MC. 
May be a late question now but where is the proper place to probe the lumber?  Obviously getting a different number when I prove the end vs the face.  It's only 4/4 stuff but I hate sacrificing a board by probing

btulloh

Pick up an older microwave that somebody is ditching or off craigslist.  In this case the gf is on firm ground.  I wouldn't do it in the house either, even with a dedicated mw.  You can, but .... interesting fumes come out of the sample.  It is really instructive and useful to try the oven dry method even if you don't use it all the time.  There are multiple threads on here about using the microwave oven.
HM126

Ianab

Yup, the microwave ends up smelling of whatever wood you happened to be cooking. As well a boiling off the water vapour there seems to be some resins and other chemicals come out as well (same as any high temp kiln) Likely depends on the wood, but any species of cedar is going to leave something behind.

And then if you use too much power, and set fire to the wood, you have a whole other smokey mess to clean up.  :D
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

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