About the misleading year per inch drying rule

Re: About the misleading year per inch drying rule

Don Stephan

People who don't have an accurate moisture meter need a guideline for how long to air dry lumber before bringing it inside. The "inch per year plus one year" guideline would seem, lacking any better approach, likely to bring lumber down to about 10% moisture content and ready for additional drying in a conditioned space for six months before using to build furniture. Less time might be needed, but is it better "safe than sorry" when an accurate moisture meter is not available? And when wetter than average years and/or less than ideal drying facilities are possible, should a guideline be the minimum or more conservative?

In the example presented, the thickness of the rough lumber dried in the barn loft is not given, but if 5/4 it was dried for one year per inch of thickness, and if 4/4 it was dried for one year per inch of thickness plus one half year.

According to the description, the 16/4 slab also was dried for 1.5 years, but was not ready to be brought into a conditioned space because it was not yet at 10% moisture content. In "Understanding Wood" Mr. Hoadley offers a chart giving the moisture content of green black cherry as 58%. If the 4" slab began with a similar moisture content there was significant drying in that 17 months, but the rate of drying is not expected to be linear, and it is a matter of conjecture how many more months would have been needed for the slab to reach 10%.

WoodCentral is a valuable forum because there is an ongoing exchange of experience, understanding, and opinion. Those lacking an accurate moisture meter (and an understanding partner willing to allow use of the family oven to measure moisture content) it might be extremely helpful to hear a better guideline to "one year per inch plus a year."

Re: About the misleading year per inch drying rule

John K Jordan

>>>Those lacking an accurate moisture meter (and an understanding partner willing to allow use of the family oven to measure moisture content) it might be extremely helpful to hear a better guideline to "one year per inch plus a year."



Based on my reading and experience there is no useful rule of thumb for all species. For example, 4/4 eastern red cedar dries much faster than the 1yr+1 and dogwood and black locust seem to take much longer. I'm sure the free water content makes a difference too; boards from the same tree seem to dry faster if that log was standing on end to drain before sawing. Too many variables for a simplistic "rule".

A simple toaster oven is $20 or less new (almost free at a yard sale). A simple moisture meter is about the same or less.

There is the weighing technique - weigh, write down the weight, repeat every few months, chart the weight as it asymptotically approaches EMC. Just need to test one sample out of a stickered stack and the others will be close.

JKJ

There is no useful guideline

Bill Tindall, E.Tn.

A modern dry kiln can dry 4/4 cherry in 4 days, oak in 30. At the other extreme, in a cool damp location any species of any thickness could stall at 12-14% moisture content and stay there forever.

Drying rate depends on these external factors in more or less order of importance: air flow, relative humidity, temperature.

Drying rate depends on these wood factors : species, thickness, grain orientation. A 20" diameter fire wood log will dry in a year because the rate out the ends is about 10 times the rate through the sides.

The 4/4 cherry that went up in the loft was low enough moisture content to use within days of the loft getting hot. The next 6 months it sat there with little change. On the other hand the 4" plank would never have dried in the damp poorly circulated environment it was stored at.

" was not ready to be brought into a conditioned space because it was not yet at 10% moisture content. " It is unlikely any lumber stored outside will ever get to 10%. Most places do not experience temperature and humidity conditions to enable it. However, lumber can be "brought in" at any time it is convenient.

Re: About the misleading year per inch drying rule

John K Jordan

This is a useful document for anyone wanting to learn more about air drying lumber:

https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr117.pdf

In particular, Table 3 on page 15 gives an idea of the EMC you can expect wood to reach for various areas. When I did the oven-dry moisture check last week on small samples cut from a larger blank the EMC was almost exactly the value given in the chart for this part of the country. Local conditions and particular years can vary, of course.

I've saved the PDF for quick reference. I'm thinking of investing the the printer ink to make a hard copy for the shop.

JKJ

Re: About the misleading year per inch drying rule

Sgian Dubh

Don, here in the UK air dried timber, dried outside, of any thickness is very unlikely ever to get much below 18% MC in any part of the country, except perhaps in the south east near London. Timber air dried in a shed with good airflow usually gets a little lower, perhaps 14 - 16% MC. Thick stuff, say 4" or 5" and thicker, purely air dried, might never get below FSP near the wood's core. Large oak beams of this type if installed in a habitable building continue to lose moisture after installation, also meaning they get stronger.

I agree that the one inch per year guide isn't particulalrly accurate for many species.

As to oven drying, there's always the option of using a microwave oven as described here: http://www.richardjonesfurniture.com/Articles/microwave-dry-wood/microwave-dry-wood.html Slainte.

This is a valuable reference for air drying

Bill Tindall, E.Tn.

I was not aware of this publication. Everything I have learned over the years is summarized in this document.

Must reading for anyone contemplating air drying lumber....or alternatively ruin many dollars worth learning this stuff by experience.

It also lays to rest any notion that the year per inch "rule of thumb" offers any useful guidance.

Thanks for this JK

Keith Newton

I'll have to spend a little time going through all of it instead of the quick scan I just did. A couple of things that jumped out to me, since Bill started this thread with Black Cherry, is that they didn't show a sapwood % for that species. Also, did you notice the highest 249% for Western Red Cedar.

AND, I may have to pull out my George Forman grill and try it for a quick dry test between plates, and throw something in with the last batch, next time we deep fry some fish. There ought to be some good use for boiling of the moisture without exposure to air, then pulling it out before any cooling drew the oil back into the wood. Although leaving it to soak might prove useful for some small items too.

Re: About the misleading year per inch drying rule

ebd

Asked my brother-in-law a while back when the best time would be to cut a tree to have the wood as dry as possible when I worked it up for firewood. Since he's been harvesting wood his entire life, as did his father, and his grandfather I figured he's know.

He told me to down the tree in the heat of summer - late July/August - and let it set till the leaves were completely dry because they suck the water out of the wood. It worked. Huge oak and the wood was almost dry enough to burn when I worked it up.

I don't see why this wouldn't work for wood that was going to be turned into lumber and turning blanks.

Re: About the misleading year per inch drying rule

Barry Irby

I have enjoyed this thread...

I think Bills statement that there is no useful rule is correct.

As a woodworker I have harvested about 10,000 BF of various species and stacked them to dry. Brought it indoors as needed and let it dry further and have had no trouble. Also green turned about a hundred bowls. Some turned green and let warp and some twice turned.

As a home inspector I was taught that wood equilibrates to an MC about 1/5 RH and that seems to be true, but its a moving target since RH changes all the time.

Leaf-drying and other methods

John K Jordan

>>>Asked my brother-in-law a while back when the best time would be to cut a tree to have the wood as dry as possible...

He told me to down the tree in the heat of summer - late July/August - and let it set till the leaves were completely dry because they suck the water out of the wood.

Brothers-in-law are always the authority on everything. If you don't believe it, just ask them!

I haven't heard of the leaves sucking up all water as they struggle to live but it doesn't sound impossible. I can understand how the leaves might draw water from the sap wood but could they also pull the water from the heart wood in the center of a 30" white oak?

An experiment to test the leaf-drying method might be to cut two nearly identically trees at the same time, immediately de-limb one to remove all leaves, leave both undisturbed until all the leaves are brown on the one, then cut a piece out of the center and test the moisture.

There are several things I've read to consider about when to cut trees, probably more.

One method is to kill the tree nearly any time by girdling then leave it standing dead for a while. I understand this is sometimes done with tropical trees. Since it is off the ground the bugs are less likely to invade. Since it is standing vertically, free water in the pores can head towards the ground. If there is anything to the leaf-drying method it might play a part too.

Another is to cut the tree in the dead of the winter. The experts I've read said that gives you the best chance of having white holly and probably for other woods that stain. Another reason is a tree on the ground in the winter is less likely to be infected with powderpost beetles, grubs, and other things that eat wood. Another reason is to keep the bark tight if you like to turn natural edged bowls or want slabs with bark. And that the sap is "down" might mean less free water in the tree but that's a guess.

JKJ

some flaws in that reasoning

Bill Tindall, E.Tn.

This claim would be easy to test. Cut tree down and immediately lop off a block from the butt end and measure its moisture content. Wait till the leaves wilt after which time they are no longer able to replenish moisture by moving moisture from tree trunk to leaf. Cut a section out of the trunk up from the end so as to not be influenced by drying out the end and measure its moisture content. I bet anyone that does the experiment a free dinner that the loss is insignificant for any tree species that has mostly heartwood. I think the water in the trunk's outer capillaries will suck out the leaves but not the moisture in the interior on the time scale of the leaves wilting in August. If I recall correctly they will begin to wilt in hours. Given the heat of evaporation necessary to evaporate water from the leaves I think the leaves would freeze if they evaporated a significant amount of the trunk's water in a day.

The worst time to try to amateur dry lumber is in the summer. The problem is too rapid drying and downgrade that results from too rapid drying, and staining from drying when it is hot.

As far as the forest is concerned the best time to cut is dormant. The stump has a high probability of resprouting which gives the desirable species a head start on regrowth.

I have been told by people that ought to know that there is no significant difference in moisture content of a tree dormant or growing. Personally, I have never tested to see.

So What Advice Do We Give Others?

Don Stephan

Everyone known as more than an occasional woodworker is going to be asked occasionally by family, friend, or neighbor how long to air dry wood they want to have sawn for furniture. Often it will be someone who wants to make, or have made, a family piece from a family tree.

A commercial lumber mill with large scale kiln is not an option. Seldom is a small scale commercial kiln an option.

So what do we tell them? Give up on the idea of a family heirloom from a family tree? It's a ridiculous idea? You will have to spend ___ thousands of dollars to build and operate a small scale kiln?

Do we take some time to give them enough understanding to proceed if they wish with guidelines (there's that "g" word again) about how long it might take?

Do we tell them only a select few know the secrets and the homeowner has to pay them whatever money is demanded to get lumber ready for furniture construction?

my advice would be......

Bill Tindall, E.Tn.

1. To ensure success "hire" someone that has experience to either do or at least advise.

2. If they want to learn, then study the reference John provided, follow what is best practice and hope for the best. Practice on something easy to dry and cheap. In spite of the fact I have dried thousands of bdft of lumber I never attempted to dry oak. Too hard to dry and too easy to screw up. I would never try to dry easy to mold species in the summer.

3. It is foolhardy to attempt to build furniture from wood that is unknown moisture content. How long it has sat, wherever, is no guide as to whether it will be suitable. "This lumber is dry. It has been in a barn for XX years." I have heard it dozens of time and it provides no clue as to how dry it is (or the quality of the drying).

4. Anyone truly qualified to build this heirloom will be able to determine if the wood is suitable. For example, I can get a good estimate of moisture content just by feeling the wood and especially feeling the shavings.

Re: my advice would be......

John K Jordan

I was going to say the same thing as Bill - at least get someone with a mill and some experience to cut it. Lots of people who have mills will saw for others but some, like me, won't do it for money - that makes it a business. I either do it for free for friends or for "shares" - they bring the log, stay and help, we divide the wood. Drying would be their problem. For an heirloom log I think I'd send them to someone with more experience.

I have sawn and air dried some of nearly every local species and have had mostly good luck but some interesting failures. The oak I've dried, both red 4/4 and white 16/4 has dried to suit me but I don't make much furniture. If so, I'd cut it a little thicker and plan on planing out the warp.

My most interesting wood was 8/4 and 10/4 persimmon. It dried fine with no cracks but cupped with enough strength to lift the weighted stickered stack! That didn't hurt what I wanted it for - spindle turning stock.

For narrow boards, I think some people still use SDR - saw-dry-rip. Instead of sawing 6" wide boards, for example, saw wide planks (flitches) through and through, sticker and dry, then rip into boards. This is supposed to prevent a lot of loss by warping. The times I've done this it worked well. I stacked and dried flitches from the entire log then when dry put them back on the sawmill and and ripped.

This is one stack of 8/4 cedar, probably not a fair example since cedar is so easy to dry anyway, doesn't even need much weight. I'm still using some of this nearly 10 years later.

JKJ

water movement in trees

Tom dunlap

What I've been taught about trees and the water inside is that water inside the cambium and a few more growth increments doesn't move very much.

Bills got it right.

Re: my advice would be......

Larry Clinton At Frankfort, (Central) Indiana

Bill, I think your advice is spot on. As far as Oak, (all species), there is no way I would attempt to air dry.

The only defective lumber I have ever gotten from my local saw mill was Kiln dried white oak - the lumber in question was 4+ inches square, and had a lot of interior checking when I tried to use it. The cost vs driving time to the sawmill was close enough that I just scrapped it though I am sure the mill would have refunded my money.

One thing I have learned is that the Amish apparently have many secrets to successfully air dry all species of wood. I purchased several rough sawn white oak boards at one auction

that was apparently air dried, these ranged in width from 12 to 14" were a strong 4/4 thick and 12 min long. I did not find one defect after planing and all were almost dead straight without bow or warp!

In fact I have never purchased any lumber from the estate sales of the Amish or old order that had drying defects! As far as I know none of the lumber was kiln dried, most tested with my meter under 15% and were stored in unheated sheds!

I normally sticker this lumber in the upstairs of my heated/air conditioned shop for a year or so, then tight stack it, at this point it was always under 10%,

If you are wanting crotch wood, don't expect it in

Keith Newton

any forks from a tight V. As the smaller stems grow, they can only tighten against each other capturing the bark. You need to find trees with a larger U between the branches. This allows the bark to be pushed on up and out from between them as they grow larger. Then due to the gravity trying to pull it apart, the grain to form swirls from each side which crisscross and stitch together to resist splitting.

I've got some cherry like yours that I sawed about 5 years ago with a long bark inclusion that I've cleaned out. I'm contemplating making a coffee table of the George Nakashima style with butterfly joints and dovetail corners which turn down to become legs.

Ditto black gum and the King of Cup

Bill Tindall, E.Tn.

I once had a close association with a small commercial mill. One day I was offered two nice black gum logs. I was about to learn why this lumber doesn't show up as a common commercial product, which is why the mill had no market for the lumber from these logs. It sawed pretty white, clear boards. I stacked it and then 500 bdft of walnut on top of the gum stack. The gum stack lifted the walnut stack! That warp, twist, crook, bow and cup plus staining ( the litany of drying defects) was just the start of this mistake. The grain was interlocked in rows about 1/2" wide. The lumber could have been perfect for a planing smack down to see who could best plane troublesome wood.

The King of Cup is cherry with sap on one side and heart on the other. Someone noted that the moisture content of cherry sap was not listed. I believe it must be 300% Relative to heartwood it shrinks greatly. Gutters and troughs can be fashioned from the first board sawed from a log that contains sap on one side only, if dried in a stack with insufficient weight on these boards. Commercial kilns mitigate this problem with stacks 20' high and hot high humidity that plasticizes the lumber in early drying.

Indeed, one can't miss drying cedar. Poplar is easy too, but staining must be avoided. Poplar, cherry, and walnut were the only species we risked drying, risk being defined as having $1000 or more invested in the stack to be dried. A stack of oak can be ruined with just a hot August day.

Interesting, I ain't skeerd of no ghosts

Barry Irby

I learn a lot here...Thank you to all who have contributed to this thread...

About six years ago I got a windfall. A huge white oak fell on one of my rental houses. Fortunately the tenant had moved out ten days before. $22,000 in damage. I (not knowing any better) took the tree to a sawmill and had it quarter sawn and stacked it in the corner of my driveway. On the bottom of the stack are a number of flitches or live edge pieces they sawed out of large limbs.

The wood has air dried and I have made several things out of it. A desk and a top for a sideboard and a number of reducing strips. So far I haven't found any defects I can attribute to drying. All the pieces I have pulled have been nice and flat and straight.

Apparently my ignorance has paid off. I didn't know you weren't supposed to even try to dry white oak. I feel lucky.

well, then,

Bruce, a MN Galoot

How does oak get dried?

Very Carefully?

I dry oak

Tom Sontag - St. Louis

Oak can be dried, it simply wants to be dried s l o w l y .

So stack it out of the sun and wind and rain and let it dry itself.

I agree that cherry with sapwood is a nightmare. Solution: cut off the sapwood and avoid the issue.

Persimmon, gum, sycamore, cottonwood all like to warp a lot so just QS them. This is difficult with a 14" diameter persimmon so we cut extra thick and frequently end up with smaller usable lengths. Another possible solution is to air dry under clamping pressure; the weight of a pallet or two of lumber is not enough for some of these.

None of these are insurmountable problems but I suspect lots of wood gets wasted learning.

How to dry oak?

Bill Tindall, E.Tn.

In very tall stacks in the SC sun, in the winter. In the summer the lumber goes indoors and out of the direct sun. After 30 days it goes into the kiln where moisture is removed at a controlled rate until the lumber eventually reaches 7% MC.

Re: Leaf-drying and other methods

ebd

Actually, the oak I cut was more than 30" diameter - and though there are nay-sayers - it worked. The wood was nearly ready to burn by that fall/winter.