Friends:
I store wood in a non-air conditioned space. I have a good moisture meter and understand moisture equilibrium. I am also about to pick a couple thousand board feet of walnut and q-sawn white oak that I cut a year and a half ago and left with the mill. All this had led to some contemplation, viz:
1) Very few people have humidity controlled wood storage;
2) Most woodworkers live in more or less humid places;
3) In humid places, even kiln dried lumber will go back to equilibrium at a higher level than is generally recommended for furniture;
4) In the days of yore NOBODY had climate controlled storage.
So, what’s the point of the kiln except speed for the sawyer? What good is advice that lumber be at 6% to 7% for furniture making? Don’t we really just want the stuff to be stable in the shop and not to move too much when it goes in the house?
Joe
Replies
Hi Joe ,
You have brought up a lot of good issues as to storage and such .
To try and answer your question why use a kiln or for that matter why use kd wood .
I think by properly kiln drying some lumbers you can preserve the true colors more so and prevent spalting , mildew and any undesirable others .
Also the lumber will have a tendency to move and wander more when air dried in my experience , the kiln will produce a more stable lumber .
You are right about wood constantly able to change as it's relative Humidity factor changes . Even the driest kd lumber when put in a damp dank place will pick up moisture then again in a warm place the RH factor will change .
It's just my observation and opinion but with some species it seems air dried wood move and changes more then kd wood does , so stability would be the # 1 advantage of kd .
dusty
The point of the kiln is speed, period, in my opinion. Not to get it down to 6%, but down to 12% quickly. To dry below local 'shop' equilibrium is futile, right? The point is speed, and time is money.
Brian
My suggestion is a book: Understanding Wood, available right here, from Taunton Press.
It will change the way you look at wood, as well as answer your question about kiln dried wood. I learned a lot, after thirty years as a Carpenter.
Good luck!
Joe,
I have asked the same question of a guy who studied forestry and wood science at Penn State. He agreed that speed of drying was a major reason to kiln dry wood, but also pointed out that wood has a memory. If the wood has been dried properly, then when it reabsorbs moisture, it will do so in the same way it was in the kiln. If it was flat in the kiln, it should stay flat.
Lots of folks use only air dried wood. If you have the time and proper storage conditions, then I think that walnut, for example, looks nice air dried than kiln dried.
Hope that is helpful.
Doug
When eood has been dried to below the 14% level, even if it picks up moisture, you can bring it back down. Speed id the point of a dry kiln, the general rule for drying wood inside is 2 years for the first inch and one year for each additional inch. In the past, (and i'm talking years ago) moisture control was not such an issue when making furniture, as there was so much to do in the summer months, furniture maling was put off till winter. In the old wood heated shops, in winter relative humidity was very low, so in effect the wood being worked was generally below the 8% moisture content.
Hey Joe,
About 7 or 8 years ago, while my dad was still alive, we bought a couple hundred BF of knotty white pine to make tongue and groove paneling for our hunting camp. At that time I had an interest in a large plant that had a climate/humidity controlled clean for assembly of elctronic gas meters. I stored the bandsaw milled lumber (not dried) properly stickered for about 6 weeks or so, and then planed to 3/4" and tongue & grooved (shaper not hand plane). I didn't check moisture content before storing, but I milled when it got down to around 9 to 10% content (we don't keep heat in the camp, only when we're there). Installed the paneling and shrinkage has been minimal. I painted all sides of the pine with clear shellac. Looks damn good!
T.Z.
My wood is stickered off the ground in a dry basement with a dehumidifier set at 35%. Sounds climate controlled to me.
FB
Joe there are good reasons for kilning wood to a target of 7% MC. In many ways the following discussion doesn't help you because you are just a small bit of grit in the wheels of commerce, but you should find interesting information in the following text-- it's a bit long, but be thankful I've not included the full version, ha, ha.. Slainte.
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Commercial lumber yards and kiln operators in North America that dry lumber (timeber) for furniture makers, flooring manufacturers, shopfitters, et cetera aim their product at their biggest customers. The main customers are the large furniture manufacturers.
Drying to a little below the MC range furniture experiences in service anticipates some moisture gain after the wood leaves the kiln during stacking into packs, banding, end painting, transport, storage and construction. There is also the issue of tension and compression forces on the likelihood of failure in glue lines, for example in panel glue-ups.
Wood used as furniture in residences, offices, hotels, conference centres, etc, generally hovers somewhere between about 7.5% MC and 10.5% MC in service. This is the middle of the range and it’s likely that many items of furniture reach a lower moisture content and others stray up towards 13- 15% MC. It does depend on where the furniture is located and other factors such as long term storage when home owners move house.
Mainland European and British kiln operators generally dry furniture grade wood to a target moisture content of about 10% to 12% MC. This seems to be a hangover from earlier times when houses had single glazing, were draughtier, poorly insulated and rarely had central heating. This meant that average atmospheric RH values were higher throughout the year and wood kilned to 10% MC would be in the middle of the range that furniture would experience. Today in this country we are much keener on saving energy, and on environmental issues, so our houses have better insulation, double glazing, and are drier and warmer. In response to this there are moves afoot to lower the target moisture content of kiln dried wood to 7% or 8%MC which is close to the standard aimed for in North America and some other countries to satisfy the needs of the large industrial furniture manufacturers.
Once the wood has reached its target moisture content the owner of the kiln or yard is keen to keep their product as close as possible to its dried moisture content. For instance, it isn’t good business practice for a large commercial kiln operation in North America to allow the timber (lumber) they’ve expensively and carefully dried to 7%MC rise to 10% or 12%MC between their kiln and their customer. A rise to 8% or 8.5% MC is probably acceptable to most of their clients, but much more than that and there would be complaints and returns.
Large kiln operators prepare and deliver a package to their customers, and they do this by cutting all the boards to the same length, close stacking the wood into a neat bundle and banding it; they frequently paint the ends a uniform colour and even paint their company logo on the side of the pile. Additionally most of these bundles are finally wrapped in a good quality plastic sheeting with the company name and logo printed on it, and this sheeting further shields the wood from changes in atmospheric humidity, rain, snow, and so on. What’s delivered to their clients is an even, neat, clean, and attractive bundle that is easily moved around by forklift, stacked, loaded and transported all around the world. Large furniture making companies, timber agents, exporters and timber merchants can easily handle, store and use or resell the stock they receive from the large drying operations.
At the home owner level of the retail trade most of us have seen the small bundles of planed softwood all cut to the same length wrapped in plastic at the large home improvement centres dotted all over our towns and cities. This sort of packaging appeals to the occasional user of wood for small DIY (do-it-yourself) projects around the home. It’s an expensive way to buy wood and professionals by-pass such outlets and go to the trade suppliers where bundles of the same or similar material are larger and cheaper. Nevertheless, the principle of providing an attractive and conveniently packaged product to customers stretches all the way from the DIY’er to the large or multi-national timber dealers and buyers.
It’s only at a certain level of woodworking that wood buyers enjoy ferreting through dirty, dusty and untidy piles of boards in search of that special plank full of interesting burls, inclusions, knots, cracks and shakes. Based on my own experience this type of buyer is most likely a small business or keen and knowledgeable amateur. These woodworkers are more likely to specialise in creating characterful craft items for their own enjoyment, or for the more expensive end of the craft furniture market, sculptured wood or wood turnery items typified by sales through galleries, exhibitions and word of mouth.
richardjonesfurniture.com
Richard,
It's interesting to note that 10 - 12% is a normal target for kiln-drying in Blighty; but that they are thinking of making a lower percentage the norm.
I keep all my timber in a fully insulated outhouse that has the same atmosphere (temperature & humidity) as the rest of the house. Timber in there rarely moves from 11%, or so my moisture meter says. Furniture in the hoosey is also at this level.
The shed has low heat all the time, basically to keep rust at bay. The humidity meter on the clock says it's between 55 and 65% (whatever that means) but timber kept in the shed for a few weeks also stays at 11% moisture content.
It's true that a lot of folk these days go for the "sealed house" approach to keeping their gas and lecky bills down. My neighbour Mr F, who is 87, does this - to stay warm, reduce costs and avoid drafts on his frailty. The pieces I've made for him now have 7 -8% mositure content. However, the atmosphere in there is far too dry/stuffy for me so I keep an airbrick or three in my own otherwise well insulated hoosey.
***
Some of the thicker timber I have, which has come from sources involving kiln-drying at some stage, has case-hrdening. This seems absent from old reclaimed timber, however thick (some 8" x 8" old beams for example). Is not kiln-drying the major cause of case hrdening? will it not get worse if the mositure content is driven down to 7% rather than 11%?
Lataxe
Lataxe, it is true that kiln drying is more likely to cause case hardening and other faults such as honeycombing than air drying. It is not true that air drying eliminates all such faults for even air drying can be too rapid, the cause of the faults.
The only reason for case hardening to occur if wood is dried to 7% or 8% is if it is dried too rapidly or the case-hardening relieving process is botched. Conventional kiln drying schedules generally purposely induce some case hardening as part of the process. To get rid of this there is a case hardening relieving procedure undertaken at the end of the kilning operation.
A danger of air drying is too slow drying. This too can lead to problems, eg, mould growth, too slow a turnover of stock leading to unprofitability, etc.
Bear in mind this response looks at commercial enterprises with their need to make money, not the needs of the hobby woodworker or other circumstances where financial imperatives are not so important. Slainte.richardjonesfurniture.com
As a supplement to my earlier reply Lataxe, you might find of interest this link to a page at my website that describe and illustrate some drying faults. Slainte.
richardjonesfurniture.com
Edited 3/28/2009 11:24 am by SgianDubh
That was a very informative link, thank you
Both very interesting, Richard. Thank you. For the practical purposes of this tiny bit of grit, however, I gather that as long as the wood is not structurally damaged by the drying process, is in equilibrium, one piece to another, and is near the mid point for its expected environment, all is well? That is what I have always thought, but decided to revisit the question in view of this load I am getting this week (all air dried for a year and then kiln finished, BTW). Joe
"all is well?"
In general, yes. There are some caveats, such as building furniture to allow for the expected maximum range of movement, and other small conditions to watch for, but the answer I've given is reasonable I believe.
You would certainly not, for instance, choose kiln dried wood at 7% MC to build exterior furniture much as you wouldn't choose air dried wood at 20% MC to build interior furniture without some further acclimatisation of the wood in both instances. Slainte.richardjonesfurniture.com
Richard,
That is purfek information - all data and explanation with no spurious woffle. Splendid! And now in my favourites as a permanent useful reference.
Lataxe.
Can't resist ;-) Here in the USA an outhouse is your Loo. So store your lumber where you may. :-(Work Safe, Count to 10 when your done for the day !!
Bruce S.
Bruce,
Why man, bein' a Geordie lad Ah calls the place wherein dark friends are sent off on a long journey to the sea "the netty". Where does this come from? Ah divn't knaa but it might be from the Italian "gabbinetti"......
Now, that outhouse of mine is in fact attached to the hoosey but used to be a sort of add-on bit with a single skin wall and concrete flloor where the washing was done. This involved boiling up clothes in a big copper boiler on a gas ring, poking at them with a big wooden stick with three knobs on the end. When they were well boiled, the rags were 'ooked up into a hand-wound mangle, which squodged oot the water.
This was a regular chore for all wifeys, who had muscles of steel and very bad tempers as a consequence. They all wore turbans and smoked a fag dangling out of the side of their gobs as they worked. Their hands were very wrinkley and red, partly through the washing chores but also because they used them to slap the children and husband on a regular basis.
These days we have a nice washing machine that requires only a gentle loading and unloading by the hand of a fair damsel made of honey with a little bit of spice in her. Mine has the hands like the queen of the elves's.
Lataxe, who has rebuilt the outhouse so it is an inhouse fit for lovely wood to lie in.
What?
Joe, try this Hearne Hardwoods on air drying hardwoodshttp://woodtreks.com/how-to-air-dry-lumber-stack-it-and-check-for-moisture/336/Ron
Jammer,
Yeeh sed yi wez in Blighty once so hoocum ye cannae taalk the lingo man?
Lataxe
He's not alone. Remember a Ken Loach (?) movie called "Riff-raff" about a group of workers on a building site in London? A Scotsman, an Irishman, a Scouse, a Geordie, a West indian, etc. (Sounds like the buildup to a joke.) They showed it on public television in Canada -- with English subtitles.
Jim
jim,
love that loach. but cannot grok a word of what his very good actors are on about. but love his stuff, i do.
eef
Me too. That funeral scene in Riff-raff made me quite nostalgic. Where else but Scotland could you get kicked out of a cemetery for fighting over your mother's ashes? I used that movie to try to persuade Canadian students that Brits 15 miles apart can have quite different accents, but since they couldn't understand a word of it, even with subtitles, I don't think the message got through. All young Canadians, except Eastcoasters, sound depressingly alike.
Cheers, Jim
Don't get me started...I'll introduce you to the Language Of Dude.My apprentice taught it to me. I'm not fluent."Good morning, Apprentice.""Dude!"Translation: "Good morning, sir. How was your evening? I, myself, slept well. Let me set down my lunch, and I'll you some coffee. I should also inform you that I seem to have misplaced my hardhat again, and I am seriously reconsidering your generous offer to duct tape it to my silly little ####."
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