Thread: When would you prefer air dried over kiln dried timber ?

Hi Jake,
Personally I would prefer air-dried/seasoned over kiln-dried.
Kiln drying can reduce pigment in wood.
Also, I would wonder about it making it more brittle.
Air drying is simple and leaves the wood in as natural a state as possible.
There are some exceptions, very oily woods which actually become harder and stronger when the oils are cured.

I'm sure some experienced woodworkers have reasons they work with or prefer kiln wood, I'm not saying I'm right, just why I make the choice that I do at the moment.
I know air drying takes time, so it's not convenient, but in another way it's easier.

For most people for most uses there isn't much difference between kiln and air dried timber. For bending, air is generally better as the heating in a kiln changes some of the properties. If you use hand tools a lot you may notice a difference in how it works. The other considerations is insect infestation, the heat from kiln drying could kill the insects and egg to stop an infestation.

as far as woodturning goes, definitely air dried

thanks for the responses.

I bend timber. from my experiences, kiln dried still bends a bit, but nothing like when its air dried.
Turning as well is a big part of my work. And I agree its better done air dried.

The only time kiln drying helps for me is, is when its done in the shop. Not, when its purchased kiln dried already. And it concerns the glue up of chair seats and drying tenons.

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With chair seats, uno how a glue line can sometimes begin to open starting from the end grain, because the end grain looses moisture faster. And also maybe a slow release of tension from the crosscuts. Big problem when it happens.

To fix that I kiln dry in the workshop at about 45C (depends on the timber). force it to move before glue up, then rejoin.

eg. Say I've got a seat blank comprising of two parts that I want to glue up. (approx say 10% moisture) I'll joint both fits for a good gapless joint (slightly sprung)….then stick it in my kiln and keep an eye on it.

Every so often I'll get it out of the kiln, hold the pieces together to check the glue line match…..and literally watch how the joint line distorts at the end grains (both ends). Wanting to see it move as much as possible. moisture meter will read 0% on the end grain. When I'm convinced its done all its moving, it comes out of the kiln to let it cool and generally reaclimitize.

I'm convinced the process works, because after a day or so sitting out of the kiln, being allowed to reabsorb moisture (moisture meter reads end grain as gone back up to say 8%) you check out the joint match, up against the light and the ends of the joint are still open a touch (1/2 mm or whatever). Not closing up, like one might expect, as it reabsorbs moisture.

Thats when I recut the edges for a gapless fit, confident that the glue line will not split at the end grains. And I haven't had any problems since I started doing this
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The other time is again a kilning in the shop…… For my chairs, its the typical thing of kilning tenon ends only. Uno, noticing them go oval….let them cool…..then in recut them round...

The pattern is the same. I kiln the parts after as much shaping or much material has been removed as possible to reduce surprises from the kilning process.

I would say other chair makers would have similar concerns……But, yet I still get many woodworkers, including long time professionals implying inadequacy because I don't buy in the timber already kiln dried. Which is absurd, if at the very least because steam bending doesn't respond as well to it.

I've seen some good kiln dried timber. I've seen some good air dried timber. And I've seen both processes produce absolute $h!t too. It comes down to operator, environment, and downstream storage.

Saying one is better then the other is foolishness, and there can be a huge difference in the properties of the same species depending on what type of kiln is used... so saying KD is better because it's been through a kiln makes no sense at all. It's all relative anyway... I can KD, and I can write out a certificate that says this timber has been dried to 10% moisture based on test sample analysis... but it can be at 13% a week later depending on the weather. Kiln all you like - the wood will go to EMC and fluctuate from there regardless. Making it go to 10% MC faster rather then slower is all that a kiln really achieves... well that and case hardening and washing colour from the timber.

The phrase marketing ploy would be accurate.

Originally Posted by John.G

The phrase marketing ploy would be accurate.

Thats the impression I get too……And it happening is understandable I guess….say one puts a lot of investment into a kiln, and its time to make money from it. Gota get people on side eh ? Gota support mates businesses. And if you don't support it, your the enemy This stuff never ends.

Originally Posted by John.G

I've seen some good kiln dried timber. I've seen some good air dried timber. And I've seen both processes produce absolute $h!t too. It comes down to operator, environment, and downstream storage.

Saying one is better then the other is foolishness, and there can be a huge difference in the properties of the same species depending on what type of kiln is used... so saying KD is better because it's been through a kiln makes no sense at all. It's all relative anyway... I can KD, and I can write out a certificate that says this timber has been dried to 10% moisture based on test sample analysis... but it can be at 13% a week later depending on the weather. Kiln all you like - the wood will go to EMC and fluctuate from there regardless. Making it go to 10% MC faster rather then slower is all that a kiln really achieves... well that and case hardening and washing colour from the timber.

The phrase marketing ploy would be accurate.

This!

Given my choice, I will always take air-dried... provided I know it is several years old and has been fully dried. (ie. at least a year for every inch of thickness plus a good few more for luck. )

When buying "off the shelf" I place no credence either way, especially not if it makes a price difference, unless I know the seller and trust their word.

Originally Posted by apricotripper

Thats the impression I get too……And it happening is understandable I guess….say one puts a lot of investment into a kiln, and its time to make money from it. Gota get people on side eh ? Gota support mates businesses. And if you don't support it, your the enemy This stuff never ends.

Neah, it's a bit more complex then that.

From the sawmillers point of view a kiln is about cashflow. It costs money to buy trees and turn them into planks. You have to buy the actual log, fell it, extract it to a ramp, transport it to the mill, then saw it. At which point you throw somewhere between 50 and 70 % of it away depending on species etc. Rainforest prime species - say Qld Maple - currently fetches around $250 m3. rainforest operations tend to be expensive because of the terrain etc so by the time the log rolls onto the mill its probably cost around $400 a cube. Add milling cost at about $150 a cube and we have $550. Say 50% recovery and the actual cost of producing a m3 of sawn timber is about $1100. That timber is worth (up here) about $1300 m3 green, if you can find a market for it. It's also worth about $2200 a cube KD or seasoned. Not a lot of people want to buy timber and hold it to season though - so it becomes imperative to be able to dry your timber so it can be sold. Holding packs of sawn timber that have cost that much to produce for a year or three before it's saleable is just not something a mill can afford to do. We have to kiln it so we can get our monetary investment back to buy more logs with. Doesn't much matter whether we're talking rainforest cabinet timbers or eucalypt flooring... the kiln serves the purpose of value adding our product a lot faster then natural drying does. You just can't keep throwing money into buying logs and milling them if you don't have sales of timber you bought in 3 months ago.

From a timber agents point of view it's slightly different. Buying in "seasoned" timber is a gamble in that there is no real way of knowing how seasoned seasoned is. Once timber has been dried by either means it's pretty stable, which means it can be stored with less attention to detail. It can also be flat stacked rather then needing stripping out with stickers so it takes up a lot less space and is generally easier to live with. And if it's dried then the loss due to drying degrade has already occured. Drying degrade becomes the sawmillers issue rather then the agents. As an agent there can also be liability issues arising from the sale of timber with the MC too high. Joe Average Woodworker probably won't be happy and might want a refundif his boards shrink and his job isn't pretty - but if you put a couple of hundred thousand dollars worth of timber into a major project (between timber and installation costs) and then the timber starts to shrink and gaps appear in the feature walls of a hotel lobby... someone is going to get sued. Being able to produce a test cert to prove the timber had been dried is a form of liability insurance. A reading from a moisture meter - no matter how good the meter - will not stand up in a court of law in Australia in that instance. Rather we need a moisture test result... sample boards go into the kiln and then are removed and zapped to bone dry and from the weight difference we can calculate moisture content "scientifically". That doesn't mean that the timber was at that moisture point however many months and half a country away from the kiln later... but it can be shown that the timber had been to say 10% at some point.

There's no reason one couldn't do moisture tests with air dried timber using sample boards but... over a two year project to dry a pack of timber it would get difficult to keep track of given the number of packs produced in that period.

Most guys I know prefer air dried as easier to work with. And it is just as good a product in every respect as KD, and probably better in many ways. But for the reasons above it is not something thats available in commercial volumes.

Originally Posted by John.G

Neah, it's a bit more complex then that.

yep, I agree its becomes more complex because of the larger scale monetary reasons. I don't pretend to be ontop of it all of what you've mentioned , as I work alone in a different scene. But I don't really need to be since I'm not large scale.

but how I see it based on what I feel and what you've said….(something you'd be aware of better than me I'm assuming)

if you gota go larger scale….to get enough timber…..you gota accept whats offered in those quantities…..ie. Kiln dried timber…..so if your stuck with kiln dried timber then your pushed away from some design options….. for me thats steam bending which is a beautiful technique I feel that leads to a good product.

But ultimately it becomes common to associate ' kiln dried timber ' with ' professional larger scale'

Which is the perception that bothers me. Because then the public opinion drives off that….-> if you dont use kiln dried timber -> ones not professional. -> he doesn't know what he's doing.

And thats what I've got a lot of….. but for me the truth is , I'd be a complete utter fool to buy kiln dried timber.
If I was to buy it in already kiln dried, I'd still go through the process of kiln drying it (again) within my own workshop to ensure its not going to move. Because it still can move as you work it. Probably put more effort into ensuring it doesn't move than the 'professional' scene.

I don't even have a good quality moisture meter. They don't work well on round surfaces I've noticed , and I'm not entirely shore they are as accurate as they claim anyway. I gather information on moisture content by weighing it green and making comparisons. I have a cheap moisture meter that I use just as ruff backup, and time spent drying etc etc. But the numbers one gets from a moisture meter, often are of little use anyway eg. that movement test of the glue line I mentioned above is the ultimate test. I think I'd be a fool fiddling about with a meter when there's a direct test like that. imo.

annnyway. Its just an opinion. apologies if my grammas not crash hot. Thanks for your thoughts.

Originally Posted by Skew ChiDAMN!!

This!

Given my choice, I will always take air-dried... provided I know it is several years old and has been fully dried. (ie. at least a year for every inch of thickness plus a good few more for luck. )

When buying "off the shelf" I place no credence either way, especially not if it makes a price difference, unless I know the seller and trust their word.

Who are you anyway Skew ?

have we met ?