MC readings

[Gunny]

I'm wondering: If lumber is taken to 7% MC within a kiln chamber, "equalized" for the recommended 24 hours, and then removed and stored within an unheated barn--stacked not less than 6" above the floor--how much increase in the "internal" MC should I expect to read after several days (mid-point through the thickness)? 

Without question, especially here in MI, the surface readings will increase, sometimes to 20% or more.  But will the internal MC?  Shouldn't the mid-point MC remain close to the 7%, even as surface variations occur?  I'm used to using the old Delmhorst hammer-probe meter and am not familiar with these new "surface" detection systems. 

Thanks for all the insights in advance.

[Hugh Darty]

The moisture content will equalize within a few days. The drier heart will pull the moisture in until it reachs the same as the outer layer. The same is true with drying, if the outer layer is drier it will pull moisture from the middle until it equalizes. The speed of both depends on wood thickness, temperature, whether the moisture is free or cellbound, air humidity, barometric pressure, air movement across the board surface, etc.

[Gunny]

Thanks, Hugh.  But I don't know that the question I asked was addressed.  I know (I think I stated) that there will be an "equalization" process and that the environment will affect the readings.  But if the--as I understand it--point of utilizing controlled heat, air-flow, and and evaporative process is to draw the "cell-bound" moisture from the fiber, what then is the difference in terms of registered MC between an 18% reading in my air-dried stack and an 18% reading from a load of lumber one week removed from a kiln chamber in which that same lumber registered 7%MC?

I ask this since some buyers--especially the professional end-users--get real nervous when I offer them 7% lumber and they read 18-20% once they get it stickered in their shop, less than 50 miles away.  Now, these folks use the same expensive meters as I do.  They know their wood inside and out and have been successful in their trades--often teaching  within the local college and/or Guild systems--and will not use anything which registers over 10%MC.  They know all about "free" and "cell-bound" and all the specs and terminologies being bantered about.  The whole point of using a "kiln" system to dry our wood is to provide our long-term customers with "kiln-dried" product, something which they expect to read at 10% or below before they use it.  There are too many stories floating in these parts of unscrupulous kiln-operators and of the now-worthless end-products crafted out of the "wet" lumber they sold as kiln-dried.

I ran an "old" Nyle system--the manually-contolled version--throughout the '90s and never had one solitary complaint regarding these spurious readings.  Suddenly, using a brand-new version of one of the popular units, we're reading all over the chart--from 7%-20%--just days after the lumber is removed from the chamber (after careful monitoring throughout the drying process) and stacked in storage.  I find it impossible, having just lost a huge account over this very issue, to convince people who've been building fine cabinets and furniture for 30-40 years that their readings really don't reflect the true MC of the lumber they purchased.  Many Amish craftsmen in the area have become pariahs using "kiln-dried" lumber they paid DH owners to dry for them. 

I'd just like to hear from those who might be encountering similar situations and/or have found a way to persuade experienced woodsmiths not to believe what their readings are telling them. 

Thanks again for the insights.

[Buzz-sawyer]

We have had this discussion here many times.
Remember in physics class, that all things in the universe are seeking equalibrium? Those things hot seek to be cold, cold seek to be hot..........moist seek to be dry dry TO BE MOIST.........
In my limited understanding the laws of the universe apply to wood fiber also.
So that being the case, once kiln dried lumber leaves the dry environment of the kiln, it will equalize with wath ever environment it is placed in stopping at the point where water migration is slowed by the woods changed characteristics...bout 20-30%???
So , to be fair, when wood rolls out of the door at Lowes the minute it goes out the door it begins to seek tyo be as moist as the surrounding air. It must be kept in a 6-7% environment to maintain a 6-7% content.It is unreasonable to have expectations that wood will deny the laws of physics, just because it have been in a kiln. The wood needs to be kept at low moisture content, until crafted so that it will shrink no more rather swell and tighten the seams.

[Gunny]

No doubt it's "equilibrium" we're seeking but, if that's the primary issue, wouldn't we see all wooden-fiber crafted items, from fine furniture to elegant cabinets (since they're almost always constructed within a dissimilar environment to that of the end-user), air or kiln-dried, ultimately fail to maintain their structural integrity?  Certainly none of them could survive the demands of the centrally-heated homes they're placed into. 

I'm familiar with the "space balls" the cabinet makers are using but they allow for such minimal shifts that it's an almost non-issue.  I guess I'd like a simple answer: Why kiln dry if the common understanding is that wood (a mositure-loving creature) will seek equilibrium within the external (relative to the kiln) environment anyway?   We've already addressed "cell-bound" and "free" moisture.

Those homes in our area which do not use central heating systems have furniture in them which has been air-dried and the drawers always open.  And an awful lot of drawers made from supposedly kiln-dried stock don't open in the homes with central heating. An anamoly? And I can send the responses this post is generating to the fellows who turn away orders which read over 10%MC all day long and they'll still send the product back. 

I once had an order questioned by a fellow who was going to run a bunch of molding for one of my customers.  The molder-planer guy had insisted that my white oak had been dried only to 20%.  My probes had measured 7% throughout.  The problem was never the MC; rather, the other guy had been using one of those "scratch-pin" meters.  I wonder if that might be the thing leading to the wierd readings since this new device is one of those "pin-less" rigs.  Any experience is comparison of the "probe" to the "pin-less"?

Thanks again.

PS:

If this is a redundant post, please direct me to those similar previous posts since I'm  relatively new to the forum.

[Buzz-sawyer]

Measurement of moisture below 15% is only accurately done by cutting  drying and weighing samples of the wood...the cheap meter are worthless at that degree.

You wrote
wouldn't we see all wooden-fiber crafted items, from fine furniture to elegant cabinets (since they're almost always constructed within a dissimilar environment to that of the end-user), air or kiln-dried, ultimately fail to maintain their structural integrity?  Certainly none of them could survive the demands of the centrally-heated homes they're placed into

I say
I tried to give ya simple awswer...or explaination...I ll try agaoin best wishes on your buisiness

The reason people kiln dry is to kill bugs, set sap, and as I said, The reason to reduce moisture content to the low end of the spectrum is that chances are it will not go lower (what house will dry beyond 6%?)so the joints and fittings will only tighten (Most homes are between 10-15% min in the winter)...drawers opening has more to do with craftsmanship to my way of thinking.
A centrally heated home CAN loosen up a old/rustic piece that was made years ago...(at higher moisture content)
The tolerances and assembly method are also closely related to the amount of fore thought and craftsmanship put into the piece.

[Xylophile]

GUNNY!  Go to www.woodweb.com and type in mosture meter in the search engine.  There will be a lot of information to peruse.  Maybe answer some of your questions.  I've had bundles of KD soft maple dead piled for six months or longer.  The outer boards are in the 10 percent range; interior boards in the 7-8% range.  This lumber is piled in an unheated industrial building, with little air flow.  Did you "unstick" the lumber when you moved it?  Also, you say that the surface readinig increase to 20%   Do you mean this is the EMC?  I couldn't find a EMC map of the US, but 20% seems high for MI.  Here in Kentucky it is 12-13, I think.  Should be lower in the frozen north, again, I think.  Whoops, was wrong, the EMC is slightly higher in MI, ranging 16.0 down to 12.3 (depending on time of year) in Grand Rapids, according to a study I just found on Google.  Anyway, you're lumber couldn't be any higher that the EMC in your area, unless you're adding water to the wood! 

Buzz!  Are you sure about mositure meters not being accurate below 15%?  I thought it was the opposite, that they are accurate  at moisture contents less than 25%.  I get similar readings with my pin-type and Wagner MMs on KD lumber.  I read somewhere that the good MMs read within 1% of each other.

[Buzz-sawyer]

I may have not been clear on my meaning...that if he was using a cheaper meater (like surface types) that a much better way of finding a SURE way of ending the debate over his products m/c would be oven drying and weight....

[Don_Lewis]

Below 25%, moisture meters are generally vary accurate but remember  the temperature and species correction. Above 30%, meters are not accurate but they are generally accurate enough. It would be almost impossible to see lumber go to 20% after kiln drying without being rained on. 12-14% is entoirely possible and generally in Michigan, lumber that is dead piled and stored will pick up about 1% per month. If you want to keep lumber at 6-8%, keep the storage space heated to at least 20F above the morning low temperature. Or run the heat off a humidistat set at 35% instead of a thermostat.

[Charles]

Gunny
I kiln dry to 6% then store what I have dried in the workshop basement and keep the RH around 40 to about 45% this wil keep the lumber around 7-8% MC
Like the guys have said 12% is 12% I did take a load back out to storage once brought it back in after a year and it was 12% dried it back down to 6%
like they said leave it outside and it will slowly go back to the area EMC here it is 12%. A furniture mfg. here kiln dries to 6% then stack stores the lumber outside in a building but for no more than a month before it is used.
The EMC in a average house in the winter here is 6-7% and in the summer 8-10 If the summer is very humid then more and the drawers stick.
The guy that said your wood was 20% is off his rocker I think. South America in the humid areas EMC's are only 15% or so.  How could yours be 20%

My Thoughts
Charles

[Gunny]

Now we seem to be getting back on topic--by the way, this lumber in question is not "mine"; rather, I've been brokering for a local who is relatively new to this process.  I owned/operated my own DH drying operation (along with our certified Tree Farm and bandsaw mill operations) throughout the '90s with no problems whatsoever. 

I don't recall any mention of anyone using anything less than expensive professional-grade meters.  Mine was a hammer-probe Delmhorst and the other fellows are using similar units.  And the buyers reporting the problems each have many decades of pro-experience in the crafts (furniture and cabinetry) and have all called me with readings exceeding 20%MC or, as one of the more recent fellows told me, "off the scale." None of them are "off their rockers." 

These last few posts are especially appreciated since they address exactly what it was that I'd initially requested.  Thanks much for your insights since, when an acknowledged "master" of his craft calls to tell me that his order was not dried properly, I'm experenced enough to listen to, rather than just "hear", them.  I've been around long enough to accept that these men and women know when they have wet wood delivered to them.

Also, this lumber--several MBF--was removed from the chamber, after a 24-hour equalization period,  and placed immediately into a dry, unheated pole barn with adequate air-flow.  None of it has been rained upon, yet much of it reads in excess of 20%. 

My personal business successes have always been linked to my ethical relationships with my customers, many of whom have been coming back to me for more than a decade.  And when any one of them calls me with a credible concern, I listen and I take whatever steps necessary to rectify the situation.  The very last thing I'd ever think of doing would be to tell him or her that I knew more about their needs than they did. 

Again, thanks for the interesting conversations. 

[Buzz-sawyer]

You said
I'm used to using the old Delmhorst hammer-probe meter and am not familiar with these new "surface" detection systems
and
The problem was never the MC; rather, the other guy had been using one of those "scratch-pin" meters.  I wonder if that might be the thing leading to the wierd readings since this new device is one of those "pin-less" rigs.  Any experience is comparison of the "probe" to the "pin-less"?


I have seen these some surface units and am not all together convinced the ones I used were precise..
ALL M/M measure conductivity through the wood from point to point ..A surface meter does not penetrate the surface of the wood and, therefore can vary widely due to species characteristics and stratified drying in the wood....
I am NOT an expert and am learning as I go , I miss word sentences and make typos too...I learn a great deal more than I have to offer here.......

I answered with my OPINION ..not even worth 2 cents to some... :D

I enjoy discussion and you will find this forum is not a strict on TOPIC  or on demand situation, rather a folksy , friendly discussion around a warm fire. :P ;)

[dewwood]

Gunny,
This is an interesting topic.  I believe like you that the cell bound moisture once removed via drying to 6%-8% will remain fairly stable for a period of time in an unheated building in a dead stack.  The surfaces will pick up and give off moisture quite readily but will correct again when moved to a heated shop.  I have a few questions:
1. Did you check the moisture content at the end of the drying cycle to verify the 7%?
2. Did you check some of the wood before shipping to the customer?
3. Did you check some of the wood after the customer questioned the moisture content?
4. Did the customer store the wood in a heated shop?

I can understand your frustration because something is not adding up correctly.  Like Don said 20% MC in the Lake States area is uncommon for dryed lumber, normally around 11% to 12% is EMC.  I would be looking very critically at the drying operation for clarification of standard moisture contents.

Let us know what you come up with.

Dewey

[Gunny]

Dewey:

As I mentioned, this is lumber from a rather fledgling operation which contracted me to broker their product(s) and act as consultant on their private woodlot.  We're running a light TSI/WHI on a 120-acre parcel and all parties are serious about providing a quality product.  Here's what seems to have happened--which, I've been assured, won't happen again:

A load of approx 4MBF Red Oak (most at 4/4 with about 500BF 5/4) was sawn and stickered for about 3 weeks back in late November, '04.  The entire load was then transferred to the kiln chamber and fired around mid-December.  The drying process took about four weeks when monitoring (with a Wagner pin-less unit) indicated that it was at 7%.  The load was equalized for the recommended 24 hours and all the lumber was then transferred to the storage barn and stacked upon 4"x6" skids.  I sold all of it in about 2 weeks. 

Inasmuch as most of my customers keep a steady inventory on-hand, none of them put any of the stock to use until about 7-10 days after receipt.  Their lumber is stored carefully since these are master craftsmen whose livelihoods depend upon such issues.  My first call came from the owner of a major cabinet shop in Grand Rapids, MI. who's been in the business over 30 years.  Ray told me that he was getting readings of approx 20%MC throughout his order.  A few days after that (as I was trying to work the problem out with the kiln operators), another contractor/cabinet maker called and stated that he was getting surface readings of 12% but core readings were off the scale of his meter.  Another buyer from Detroit stated that his order was degrading terribly, that he was getting cupping and large checks on each end of each board he'd had processed by the crew.  Now, throughout all this, the rhetoric and banter about EMC and "equalized MC" and absorption and so many other things that I can't even recall was being played out.  The customers continued to be unable to use a single stick of the wood.  And I've been on the block long enough to accept that all the words in any dictionary mean absolutely nothing when you sell a new car to a man or woman and they can't start the darned thing.

What seems to have happened in this specific case is that the monitoring of the load was conducted in a timely manner but the testing was only done on those boards the operator could access while squeezing himself throughout the chamber.  His readings of 7% were correct, for those boards he could reach.  Unfortunately, about 90% of the load was inaccesible and had been frozen and seems to have never released its bound water. 

So, refunds are being offered, sincere apologies given, and notes recorded for the future.  Actually, we're even suggesting that our customers bring along their own meters to test, if they so desire, each and every board loaded out for them.  Like I said, I ran a Nyle unit very successfully throughout the '90s and had never run into anything like this particular event.  Frankly, I'd like to see the guys rig-up multiple monitoring options which include readings taken from throughout the loads.  There's an awful lot of lumber that'll never be scanned with a hand-held device in a stack of 4MBF.

Thanks again for the insights.  On this end, it's always gotta be "The customer is always right."  No matter what anyone else wants to say.

[Hugh Darty]

Gunny,
Sorry for not addressing your question, sounds like you made a common greenhorn mistake . Hopefully your customers suffered no serious damage. I made the same mistake once and ruined a good set of cabinets (only one set that I know of). I learned to always check boards throughout the kiln charge when unloading and unstickering. Had to reload and finish drying once or twice but never lost another customer for this reason.

[Charles]

Gunny
I can only add that I think you are on the money here. I got caught short once and needed 100 bf red oak to complete a job which I didn't have . I grabbed a small frozen log put it inside for a week to thaw then sawed it ( was not completely thawed) and put it in the kiln. "Nightmare on Elm Street". Everything started ok for about the first 3 weeks then then everthing went out of wack . Some dried and some didn't I had readings from 18% to 9% MC . The load never did dry evenly. Some boards just give up drying. Ended up buying the little I needed to finish the job. I am not a professional drier, but maybe frozen lumber has something to do with it ??. I still have that load stickered in a dry place, it's peanuts but I'll win.

My Thoughts
Charles

[Gunny]

Hugh:

Lord knows I've made my share of mistakes in this life but this one wasn't one of them.  The kiln is operated at a site about 15 miles from my "retirement" villa here at Townline Lake and is monitored by the son of the owners of the operation.  We can only hope a lesson was learned from this miscue.

Best that way.

[Jason_WI]

I dont have a kiln setup yet but I have a moisture meter, A Wagner L605. It has saved my butt twice so far. I have my wood kiln dried by a neighbor with a DH unit. Nothing wrong with the DH unit, it's the operator that has no clue when it comes to hardwoods. Different species are mixed in all the time with oak and pine in the same load. I tried to explain nicely that oak and pine are two different animals but it was of no use.

All of my oak that was said to be dry had readings of 15% with my Wagner. Back in the kiln it went....  If you want something done right you have to do it yourself! A solar kiln is going up this spring to dry my lumber.

Jason

[Gunny]

Jason:

I wonder how it is that your neighbor failed to read his owner's manual?  I can't speak for the other manufacturers but I do know that Nyle's manual states very specifically that various species may or may not be dried within the same schedule.  Does anyone know if Ebac provides the same advice? 

Good thing you invested in that meter!  And a better thing that your neighbor believes it and the fact that you know what it says!  He could have insisted, time and again, that your lumber was just "equalizing!"

The only incident I ever had in all the years I dried for other folks was when a fellow used a two-bit "scratch-type" meter to read surface moisture instead of observing (since he didn't have a meter that allowed him to do so) core MC.  I took care of that for him with my equipment and he got a bit of an education that day.  And when it comes to all the explanations I've seen about "kiln-dried" lumber, I'm getting one, too.

Good luck with the solar unit.  I have one on the calendar for down the road apiece, too.  I might go with a small geodesic since the "delta-T" in those is humongous!  And, since I used to build them all over mid-MI, they're not as scary as they look.  Besides, if it doesn't work as a kiln, the grandkids can use it for one cool fort. 

Best.

[oakiemac]

I just read this thread with interest since I too have had similar problems.

I just put in a load of mainly Oak that was frozen. Is putting frozen lumber in the kiln a problem? Some of it even had ice on the boards which I tried to scrape off but I know that I missed some.
I noticed some mold growing on the edges of some of the boards and now after reading this I'm getting worried about the lumber.  Any advice?

[Gunny]

oakiemac:

I tried the frosty-route only once back in "the day" and filed away the experience for future use.  Not only is it almost impossible to get the mid-half of the lumber (assuming you have a pretty sizable load in your chamber) dried properly without case-hardening or honeycombing the outer edges with the heat that has to be shot to it, there's a prety good chance of staining an awful lot of the lumber since the water content is so high, sometimes even noticably dripping onto the boards below.  My chamber floor was concrete and looked like a small glacier on the move some days when I'd pop in for an MC check.  I've not seen the mold you mention on the oak but have seen it form on Hard Maple that was almost-dried in a similar environment. 

I'll never try that trick again; rather, anything that'll be in my chambers during our sometimes/sometimes not MI winter months will have a couple of months of air-drying behind it, first.  It's so much easierr on the units and electric meter, too.

That iced-load mentioned above went into the "get-it-while-you-can" pile of rejects at our store.  We still more than broke even and learned a wonderful lesson at the same time. 

[oakiemac]

O.K, now I'm in the full panic mode. I can't afford a "lesson" right now. I'm too small to loose a whole load. Guess it is time to start praying. :'(

As you mentioned Gunny the wood was extremely wet, with some dripping onto other boards. It is probably too late to do anything about it now.

What is the saying about the "good Lord watches out for fools".

[Gunny]

I certainly didn't mean to send a panic-pulse through you!  Maybe a little more air?  You probably already have 2-3 fans hitting the stack so maybe a reduction in chamber temp while more airflow is added?  Anything to keep the water from standing/sitting on the surface areas?  How much you got in the chamber?  How long's it been in there? 

I hate to even mention it but you might--to salvage as much as possible--want to pull it all and resticker it from the outside-in?  You might even flip each and every board?  On 3MBF, you're looking at a good morning's sweat-labor (I have a couple of young strong backs to help me load/unload) but that's a tidy chunk of change to save.  Maybe it's even good for the heart?

Good luck since I've been down the path, too.  And I never forget those four famous words: "This too shall pass."

[oakiemac]

Gunny,

I have 2700bf in there right now that was loaded on Feb 7th.  About 3 days ago I added another fan but it is just a small house fan. I might need to invest in a large industrial type fan.
I did go into the chamber this morning and looked everything over real good.  It might not be too bad, there is some light fluffy mold growing on the edges of some boards but it brushes right off. I'm hoping that this will all just brush off when it gets unloaded and what is there doesn't seem to be spreading.
The RH is coming down slightly and is around 82% and I'm getting about 8gallons/day of water out. Temperature is at 110 F.
Other then the mold everything looks normal for this time in the cycle.

I definately think more air flow would help. Thanks for your suggestions Gunny.

[kilndry]

Be careful with mold, especially when you are already limited in airflow. As it grows it can have a serious negative impact on air velocity between the boards as it fills up the sticker opening. Might not look like much, but if it is growing on the surface of the boards above and below a sticker space, it can quickly reduce the size of the opening. Seen it get bad enough to basically seal off the opening.

In general, the higher the air velocity the less trouble you'll have with mold, but once it starts it will be there until the wood is dry unless you go in and remove it somehow.