A couple days ago I pulled a load of 10/4 White Oak. It all read around 7% with my Wagner after 8.5 days. The core may have been higher. The next day it had cooled and I went back to look for wet pockets. Almost everything read around 10%. I never saw such a change in MC so quickly.
Do you have the temperature change and the relative humidity change that this block went through over that 24 hour period?
Or just the cooling effect on the moisture meter reading?
What's the MC of other wood nearby, Den? What will you expect that to stabilize at? 12-16 per cent?
den
does your meter have temp adjustments you can change?
Wagners aren't supposed to be affected much by temperature but I know capacitance does change. I would expect EMC around 12% but not in one day.
3% is a lot of regain in one day. Either the RH was very high, the core is still very wet or the meter is on the blink. I would bet its a wet core, if I were a betting man.
I just checked a piece of 8/4 White Oak that has been leaning in a corner for a couple years. It is in the high 11's nearly 12%. That's apparently the EMC in here but doesn't explain the low readings when I took the WO out. You may be right, 5/4, but that Wagner will "see" your hand if it's under a piece of 4/4. Also, I had no open checks in the WO. Maybe it was just a combination.
1. Did you have air space underneath the wood when you tested it?
2. The meter is expecting 4/4, so when you have more wood underneath, it thinks that there is more moisture (just like when you place you hand underneath). This is why the 8/4 read high.
3. Although the outside EMC is 12% EMC average in your area and most of the USA, inside a shop or lab, it will be 1 to 2 points dryer in the summer and maybe 6 points dryer in the wintertime.
4. The meter will respond more to what is happening at the surface closest to the plate, so initially, the surface may have been quite dry. (Test it out yourself by taking a reading, then gently wetting the surface and take a second reading. Do this on both sides of the piece, but only wet one side. Do it for 4/4 to see the biggest effect.)
5. If wood changed MC that fast, then we would not need kilns.
6. With thick lumber, the pin meter offers more reasonable readings, especially with respect to the core MC.
The wood was 10/4 - quite heavy. I just took a few readings of the pile both times.
It's been hot and humid. The surface would have regained some moisture.
I took the water out at a rate of more than 8% per day. Who needs (conventional) kilns. :D
I should have mentioned that this oak is going to a '49 Dodge dump truck that is being restored with a White Oak bed. I didn't need to worry about MC. I was just curious.