Moisture Meter Questions

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DSWalker

David
Corporate Member
You may have seen my post about drying my White Oak. I have a Dr Meter MD918 that I got off of Amazon. It was giving fairly consistent numbers [that I would have expected] on the oak when I first got it starting in the high 20's down to the mid teens about a month ago. I was using the appropriate density setting and had calibrated it following the instruction book. However I wasn't real confident that it was giving accurate readings because when I would test the Pine tongue/groove boards used for the walls of the storage room, it was always reading very high [around 20%. I had reset the meter for the proper density when changing from the oak to the pine]. Room is located inside a barn and is approximately 6 years old, so I would think it was MUCH drier than 20%. Currently keeping it at 35% humidity and about 95-105 degrees with my dehumidifier and fan blowing. It does cool a little at night, but hasn't been below 90 recently.

I brought the meter in and reread the instructions to re-calibrate. Long story short the display does not do what it says it should do during the calibration process, so I don't know if it is set properly. HOWEVER

I'm now getting a reading that seems like it would be closer to normal for the pine walls. You can see the shrinkage between the boards from running the dehumidifier constantly.
20160730_103022.jpg

AND now when I test the oak, I"m getting numbers sub 10% levels. The first 2 pics below are from 4x4's and 2x4's. The last is either a 4/4 or 3/4 board.

20160730_102810.jpg20160730_102735.jpg

20160730_102626.jpg

Thoughts? Anyone have this or a similar meter? I don't know if I should trust the new readings that I"m getting. Will Klingspor test a board for me or is there anyone in southern Wake County [Raleigh to Benson area] that might test a board if I bring it to you?
 

scsmith42

New User
Scott Smith
Two comments.

First, and foremost, based upon the last picture you have active powder post beetles in your oak. The troll-tale frass signs are visible on the board, along with the holes. If it were me I would get the lumber out of my house and thoroughly clean and vacuum that room.

Second, your pine readings are about right for an EMC based upon 35% RH.
 

DSWalker

David
Corporate Member
Two comments.

First, and foremost, based upon the last picture you have active powder post beetles in your oak. The troll-tale frass signs are visible on the board, along with the holes.
I actually started reading up today on what to do to kill any bugs that may be active. I'm not familiar with the phrase "troll-tale frass signs". Can you tell me exactly what you are looking at in the photo?

If it is the white powder you are referring to, that is diatomaceous earth [DE]. I spread it all over each layer of wood as I stacked it. It is used to help kill bugs. I have no idea if it works on the beetles, but figured it couldn't hurt anything.
 

scsmith42

New User
Scott Smith
I actually started reading up today on what to do to kill any bugs that may be active. I'm not familiar with the phrase "troll-tale frass signs". Can you tell me exactly what you are looking at in the photo?

If it is the white powder you are referring to, that is diatomaceous earth [DE]. I spread it all over each layer of wood as I stacked it. It is used to help kill bugs. I have no idea if it works on the beetles, but figured it couldn't hurt anything.
Stupid auto-correct.... it should be "tell-tale" frass signs, not "troll-tale". That's what I get for answering in a hurry from a tablet!

What I'm seeing is the combination of the pinhead sized holes in the face of the lumber coupled with the small piles of extremely fine sawdust on the face of the board near the holes. These are an indicator of an active powderpost beetle infestation (ppb).

Oak tends to be a preferred hatching and breeding ground for PPB in the SE region of the US. PPB will infect it in at least two scenarios. The first is in the log when you leave an oak log sitting for a few months before milling it. These beetle holes tend to occur primarily in the sap area of the log, and thus will usually be visible along one edge of the board (or across one face if the board is flat sawn and from the outer portion of the log). Boards milled from the inner portions of the log tend not to have the PPB infestations at first.

The other scenario is when PPB will infect a stack of green, cut lumber. In this instance they will lay their eggs across the face of the boards and then the hatched larvae bore into the board sporadically across the face.

In both instances, the larvae live inside the boards, typically boring tunnels in the wood before emerging a number of months or years later to repeat the cycle. The small, round pinhead sized holes are the exit holes. Your infestation appears to be the latter type.

DE is not a good choice for lumber treatment due to the fact that it will cause accelerated wear and dulling for the equipment used to process the lumber post drying. It will cause jointer and planer blades to dull prematurely, and can work it's way into gears, bearings, etc on your equipment and cause premature wear. It is also not an effective treatment for PPB.

The best pre-infestation treatment option for green lumber is to saturate it in a solution of boric acid. A product called "Timbor" is one of the better commercial choices for this.

The best post-infection treatment is heat sterilization. You need to heat the boards until all portions of the lumber reaches 133F or greater for at least 30 minutes. You can build a simple home heat treatment chamber from foil faced foam board, sawhorses and a space heater, or you can take the lumber to a commercial wood kiln for treatment. FWW had an article a few years about about the home heat treatment method.
 

DSWalker

David
Corporate Member
Thanks for the info Scott. Rookie mistake on the DE! I'll be sure and clean it off as best I can before milling later. The tree had been down for about a year before we decided to mill it for lumber, so they may have been there from the start. :( I did see a few small piles of saw dust and holes when I brought the second load home and thats when I decided to dust them with the DE. Wish I had found this site before!

I'm off to Lowes for some foam insulation this morning. Gonna cook those suckers!
 

Jeff

New User
Jeff
The best post-infection treatment is heat sterilization. You need to heat the boards until all portions of the lumber reaches 133F or greater for at least 30 minutes. You can build a simple home heat treatment chamber from foil faced foam board, sawhorses and a space heater, or you can take the lumber to a commercial wood kiln for treatment. FWW had an article a few years about about the home heat treatment method.
We had a similar discussion a few months ago. At that time the heat treatment chamber worked nicely for the OP but he had much less wood. You have muchos bf and they're about 10' long. :eek:

http://www.ncwoodworker.net/forums/showthread.php?t=58639

I'll be blunt! The accuracy and reliability of your "induction" moisture meter is suspect and I wouldn't trust it in a rain storm. You paid $60 for a wood moisture meter anomaly. About $150-200 will get you a good induction meter from established producers and I'm not being an elitist.
 

aplpickr

New User
Bill
I use the right cheek meter. If you touch the wood to your cheek and it feels cool, it is not dry! This has worked in my turnings over 13 years
 

scsmith42

New User
Scott Smith
Thanks for the info Scott. Rookie mistake on the DE! I'll be sure and clean it off as best I can before milling later. The tree had been down for about a year before we decided to mill it for lumber, so they may have been there from the start. :( I did see a few small piles of saw dust and holes when I brought the second load home and thats when I decided to dust them with the DE. Wish I had found this site before!

I'm off to Lowes for some foam insulation this morning. Gonna cook those suckers!
I have a copy of the FWW article that I can send you, if desired. Send me your e-mail address via PM if interested.
 

bluedawg76

New User
Sam
I'll be blunt! The accuracy and reliability of your "induction" moisture meter is suspect and I wouldn't trust it in a rain storm. You paid $60 for a wood moisture meter anomaly. About $150-200 will get you a good induction meter from established producers and I'm not being an elitist.
I like the pin style ones personally. probably a worthwhile investment for that much lumber.
 

DSWalker

David
Corporate Member
I have a copy of the FWW article that I can send you, if desired. Send me your e-mail address via PM if interested.
PM sent. Thanks!

So I built a box around the stack of lumber so I can heat it up and kill some bugs.

20160801_204853.jpg20160801_210610.jpg

I have a couple of fans blowing plus an older oil heater. Been 24 hours and it is only getting up to 112 degrees. I put an extra small electric heater in there tonight and it kicks the breaker within 5 minutes. I turned off one of the fans and am now trying the smaller heater by itself.

Any suggestions to get the heat temp up? I'm now thinking the heater thermostat is kicking the heater off and this is a hot as they are going to get without additional help.

The 'oven' is roughly 4'x 11.5' x 6'.
 

KenOfCary

Board of Directors, Secretary
Ken
Staff member
Corporate Member
Lignomat is a very good source for accurate moisture meters. The one I have (not cheap unfortunately - sometimes you get what you pay for) does not need to be calibrated. It has a density adjustment and two reading depths 1/4" and 3/4" into the wood. It is pinless.

When I purchased mine they did not sell them except on their own website. That might have changed.
 
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