Air Dried v Kiln Dried

[BradNaylor]

This thorny topic has cropped up again on a thread of Karl's over in the Projects forum.

There seem to be two camps.

I use KD timber simply because that is what is stocked by all the suppliers I know. People such as John Boddys, British Hardwoods, and Irmass all sell huge quantities of KD hardwoods to furniture and flooring manufacturers, seemingly without any problem.

My only experience of air-dried timber is a couple of small local forestry operations who plank their own wood and leave it to dry in sheds for several years. They sell almost exclusively to the building industry who use the timber in external situations or possibly for oak beams in barn conversions etc. I have tried some air dried oak for furniture and found it awful!

The other camp contends that KD timber is rubbish and that air dried is the only stuff to use.

I am far from being an expert on this matter and would love to learn more.

Cheers
Brad

 

[woodbloke]

Brad - you only need to looks at the recommendations of people like Alan Peters, David Savage and the Barnsley 'shop to realize that the only stuff they use is air dried. Savage in a recent issue of BW described kilned timber as having "all the life sucked out of it" which is a fair description. I've used kilned timber in the past thats been full of splits and it's 'carroty' when it's being worked...bloody awful :evil: to say the least - Rob

 

[wizer]

The only air dried timber I have used is this Oak from Mike. I assume it English Oak and air dried. All I can say is that it is surprisingly nice to turn and carve. Ok, so not like carving Lime, but no where near as brittle as the KD stuff.

Just my limited experience.

 

[MikeG.]

I pretty much exclusively use air dried, but only because we are short of suppliers around here and it is pretty much all that is available. I can't comment on the alternative, therefore......but thought I would mention that if you are planning to steam wood, air dried is almost obligatory.

Tom, yes, that oak was air dried.

Mike

 

[woodbloke]

The only air dried timber I have used is this Oak from Mike. I assume it English Oak and air dried. All I can say is that it is surprisingly nice to turn and carve. Ok, so not like carving Lime, but no where near as brittle as the KD stuff.

Just my limited experience.

I think one of the issues is the amount of hand work done with the timber. If it's used exclusively with machines with very little hand work, then you don't really notice the difference. It's only when the stuff gets on the bench and you hand plane it or do a lot of work on it with hand tools does the user notice the glaring difference. If you've never used good air dried stuff you also won't be able to tell the difference 'cos the KD timber becomes your reference, good air dried stuff is almost akin to working with a very hard cheese (almost)...it's that sort of consistency - Rob

 

[crazylilting]

Each wood has it's place. Those who use hand tools and those who use it for commercial applications. I've used both, and to be honest i don't think many people air dry their wood well enough to use. It's frustrating getting wood from some bloke who boasts that it is the best only to find out it is absolute rubbish for the job it was intended for.

One way around this is to have a small kiln to finish the wood off. It doesn't have to be high tech just enough so the wood is usable. I for one can not afford an inventory of wood to use several years down the line. I know a fellow woodworker that fells his own wood and stores it and yes also has his own kiln made out of a shipping container.

He has so much wood he could sell it and retire i reckon. He doesn't mess around. If the wood is air dried properly it is wonderful to work with, but chances are the wood doesn't look that great either. It's rare to find air dried wood that is of high quality in the parts where i live.

If i had the land and the money i'd do what my joiner friend does but i don't so i go to the wood wholesaler and buy kiln dried wood that is stable enough to actually do the jobs i have on hand.

 

[Doctor]

What does "carroty" mean, is it similar to "turnipy"?

 

[motownmartin]

I bought a load of air dried Oak and was going to make a large storage chest, I started to cut the legs and rails and one or two splits started to appear, no worries, I thought I could position these so they would be hidden, I proceded to plane and thickness the stock only for a lot more splits to appear, so many that I stopped the job altogether.

So I lost confidence in air dried timber.

It may have been a bad batch or somebody telling me porkies, the stuff is still moving now, I put most of the wood I use in my sun lounge for a month to give it a good drying, it's like a kiln

 

[marcus]

I wonder if there is a difference between timber that has been kilned by heat and that which has been kilned by dehumidification? I used to swear by air dried because of the ease of working, but recently I bought a big load of oak from David at Interesting Timbers that had been kilned in his dehumidifier. It was probably the best oak I have ever used (I work mostly with hand tools and hand planed everything). It planed beautifully, and didn't feel like the commerdcial kiln dried stuff at all. To be honest I couldn't have told the difference between it and air dried.

Perhaps the baking that timber receives in a traditional kiln affects the wood in a way that dehumidifaction doesn't?

Does anyone else have any experience/opinions about this?

Cheers

Marcus

 

[Paul Chapman]

I've had problems with kiln dried timber as well - lots of splits and cracks and case hardening. Also many stockists sell kiln dried stuff which has been stored in damp conditions after kiln drying.

Air dried for me every time now.

Cheers :wink:

Paul

 

[marcus]

Another thought - could it be that most timber which gets kiln dried is not that good before it even goes in the kiln? The oak which you find on the racks at your typical big commercial timber merchant is not the same quality as the oak that will be selected to be air dried for furniture making. I've used poor quality air dried timber that was just as irritating to work as a lot of kiln dried stuff you come across....

 

[woodbloke]

I think it may also depend on just how it's been kilned...often too quickly IMO which is what causes the defects to appear, 'specially in oak - Rob

 

[CWatters]

If it's anything like buying firewood then "air dried or "seasoned" can cover a multitude of sins. One place "seasoned for a year" means they cut it into 10" logs and then store in a well ventilated barn. In another they mean the tree fell down in last winters storms and has been laying on the ground where it fell ever since, they've just been hired to clear out the tree falls and will cut it to whatever size you want.

I'm still really a novice at wood working. How is "air dried" defined and controlled? Do many places properly air dry timber these days or is it just a euphamisim for "not kiln dried"?

 

[woodbloke]

How is "air dried" defined and controlled? Do many places properly air dry timber these days or is it just a euphamisim for "not kiln dried"?

It should be 1 year per 25mm of thickness...ideally :wink: Timber should be dried under cover out of direct sunlight and the rain with good air flow around the boards. These are ideal conditions which are can sometimes be found in larger commercial woodyards. At Yandles, some of their stuff is conditioned under cover but a lot more is out in the open, so you really need to trawl through the stuff to find anything that's half decent. Some of the smaller yards though may only offer timber that's been air dried as they may not have access to a kiln - Rob

 

[yetloh]

It is OK for professionals like Barnsley and Alan Peters who have the space and resources to buy in logs and either convert them or pay for someone to do it to their specification, but the average amateur or small maker has to buy what they can readily get, which is KD. I work extensively with hand tools and have occasionally worked with AD and, yes, it is nice to work with. But the reality is I have no ready source of good quality AD. So I buy KD from reputable hardwood suppliers - usually W L West near Petworth or English Woodlands at Cocking.

I have never had any problem with their timber. It may not be quite as nice to work but I think it is easy to exaggerate the difference. In the end, quality is what matters which is why I would never buy from a general timber merchant.

Jim

 

[Doctor]

I can't believe people limit themselves to one or the other, you're missing out on some good timbers.
Kiln drying changes the nature of the timber, but as for sucking the life out of it, I think not, I have used hundreds if not thousands of cu ft of kiln dried and air dried oak, I doubt I could tell the difference.
More noticeable to me is European v AWO.

But heyho, if Mr Savage says it, he must be right after all it was in BW.

 

[Sgian Dubh]

What does "carroty" mean, is it similar to "turnipy"?

Doctor, below is some information from a text I am working on that discusses 'carroty' wood. Slainte.
++++++++++++++++++++++++++++++++++++++++++++++++++

Brash wood has a variety of related names including brashy, brashness and brashiness. Additionally this condition is called brittle heart, carrot heart, spongy heart, brash heart, soft heart. Natural brashness or brittleness develops in the living tree caused by the way a tree grows and the stresses it experiences in life. In every case brash wood is weak wood and it unexpectedly snaps across the grain under a load that normal wood of the same species would carry with ease.

Brashness often develops in association with cross shakes as discussed elsewhere. In another instance it develops in exceptionally slow grown ring porous species where the tree lays down a high proportion of soft spongy and weak spring growth, and a low proportion of denser stronger summer growth wood. Ring porous species with unusually narrow year-on-year growth rings are one possible feature to look for; the result of this is that the wood is also likely to be exceptionally light for its species, and this serves as an indicator of potential brashness.

Conversely very quickly grown conifers also lay down much weaker lighter spring wood than they lay down denser and stronger summer wood and this too is brashy. Juvenile wood also tends to brashness, especially if it has grown fast with widely spaced growth rings. Unusually dense reaction wood in coniferous trees known as compression wood is often brash, and this type of wood is not used in furniture, but carvers and turners may well come across it (Hoadley, 2000, p9 99-100). Shield (2005, p 133) discusses brittle heart or brashness being the result of growing stresses within plantation grown Eucalypts where he notes that successive growth increments develop tensile stresses in their length with each successive growth increment developing slightly more tensile stress than the previous year’s growth. To compensate for this the tree develops longitudinal compression stresses towards the tree’s core. Brashness is also caused artificially when wooden artefacts are subjected over time to high heat “such as wood ladders used in boiler rooms.” (Rossnagel, Higgins and MacDonald, pp, 43- 44).

The lesson for woodworkers is that brash or brittle wood should not and cannot be used for load bearing structures, eg, floor joists, floorboards, table and chair legs, rails, etc. The safest thing is to not use it at all except for purely decorative items such as small carvings or other non-critical parts. Secondly, materials other than wood might be better choices in high heat environments such as forges, certain areas within commercial kitchens or glass blowing workshops for shelving, steps, ladders and so on.

References.

Hoadley, RB, (2000) Understanding Wood: a craftsman’s guide to wood technology, revised edition, The Taunton Press, CT, USA.

Rossnagel WE, Higgins LR and MacDonald, JA, (1988) Handbook of Rigging for Construction and Industrial Operations, 4th ed, McGraw-Hill Professional, New York.

Shield, ED, (2005) Plantation Grown Eucalypts: Utilisation for Lumber and Rotary Veneers—Primary Conversion. Economic Forestry Associates, Australia. Seminário Internacional de Utilização da Madeira de Eucalypto Para Serraria, pp 133- 139

 

[Doctor]

Interesting and very knowledgeable, "carroty" is a new one to me. However I am not a great reader of woodworking material. I personally would have described AWO as carroty due to its colouring, I call it ginger, but I suppose thats racist these days.
Can I invent a term for the soft brown / white squishy bits which can be found on occasions in ash, "bananary".
Feel free to use it in any work and I allow the term to be used in BW if wanted

 

[Mr T]

Hi

I think Yetloh has summarised the problem with air dried. To use it commercially you need a lot of pace to store it. Anyone who has visited the Barnsley workshops must be impressed by their storage sheds. However most small makers do not have the space. Yes, good air dried is wonderful to work, especially walnut, but practicallity means we used kiln dried.

I find the kiln dried oak from John Boddy's in Boroughbridge works well.

Chris

 

[custard]

I prefer air dried...provided it really is dried!

Most of the complaints about air dried on this thread seem to be about timber that was sold as air dried, but actually wasn't.

IMO you shouldn't use air dried timber unless you've got either a good moisture meter or a good and trusted supplier, otherwise you're just guessing and hoping for the best.