woodbloke":ecbi9b2k said:
Richard, I can't put an objective slant to this as I'm not party to all the technicalities of KvsA dried timber. For me, and this ia a personal view, air dried timber is just more pleasant to us. It's very difficult to quantify for me...it is just better. I'm doing a couple of projects at the moment in air dried oak (I know as I saw it in stick outside) which is fabulous stuff to use, it has none of the 'carrotyness' that you sometimes find with kilned material.
That said, I've probably done stuff in kilned material (and not realised it's been kilned) which has also been good to use (American Cherry is decent when kilned) but my view has probably been jaded by using kilned AWO which I don't like - Rob
It looks like eoin isn't going to set out his reasons for saying that air dried timber is best. So I'll respond to your post Rob.
It's my experience that you can only say that one type of dried wood is better than the other in certain circumstances. For example we've just had a project go through the workshop to build furniture for outside use. Generally spreaking it makes sense to use air dried stock here because air dried stock will never dry below about 18% MC in this country unless it's dried in covered sheds, and it's not always. Outdoor furniture is never likely to get much below this sort of moisture content either, and frequently will be above 20% or 25% MC.
Similarly if you are building furniture or fittings for museum archives and storage facilities where conditions are kept particularly dry on purpose it's a sensible choice to make these items out of kiln dried stock so that shrinkage is kept to a minimum.
I have come across badly air dried wood, just as I've been sold badly kiln dried stuff. There's a myth out there that all drying problems are induced by the kilning process. They're not as I've come across case hardened air dried wood as well as case hardened kilned stock.
It's often cited that air dried stock is kinder on tools and easier to work, and generally that is the case. Secondly, many put forward the argument that air dried wood has a greater range of colour than kiln dried material, and that too is often the case. However, to set against that those colours are often fugitive and I've made pieces of furniture using, for example, various walnuts. Usually, after about a year or two years it's hard to tell the difference in colour between air dried and kiln dried material.
Air dried material is more likely to bring unwanted pests into your workshop, eg, common furniture beetle and powder post beetle. The kilning process kills these pests, but it's true that the pests could attack the wood, particularly the sapwood, later on.
Kiln drying hardens and stiffens the wood to a greater extent than air drying-- explaining why it's harder to work than air dried stuff, see above. This is a major disadvantage if you are steam bending the wood, but it is an advantage where strength is an issue. Kiln drying, because it dries the wood to a lower MC than air drying will reveal what may be unacceptable warping in wood in a finished furniture item. You can reject it before you use it whereas you won't find out the problem until after the piece is made with the air dried material. Kilning therefore helps to stabilise the wood because it causes the cells to distort as much they are going to distort.
If you have two samples of the same wood species, one air dried down to 15% MC and one kiln dried to 7% MC and they are both at, say, 15% MC you can assume the kiln dried material has gained moisture, and the air dried stuff has never been below 15%. If you were to set about conditioning both these pieces of wood to, let's say, about 8% MC, through stickering them up inside in a warm dry spot, (eg, your house) you'll find the kiln dried stuff dries out a lot quicker than the air dried material.
These are just some of the differences between air dried material and kiln dried material. It's my experience and knowledge that says to me that it's not good advice to simply say one is always better than the other. The characteristics of air dried material are somewhat different to the characteristics of kiln dried stuff. Neither is really better than the other, but there are circumstances where the use of one is a better choice than the other.
I think it's generally best to add context and reason for any advice given. At least this way it gives the reader something solid to chew on and learn from. Unsubstantiated opinion on factual subjects doesn't really add anything useful to a discussion, and may even hinder learning. Slainte.
