When is it useful to use the kiln?
With our middle European climate, the moisture content ends up averaging around 15-20%. Even in 100 years, it probably wouldn't be any drier.
Apartments with central heating have dry air with a moisture content of around 6-10%. Floor boards which have only been air-dried would lose the last bit of moisture, shrink a little and create gaps. In this situation it is useful to rest dry the boards in a kiln before installing the floor. However the natural drying process should have been finalized before the kiln.
The resulting wood often needs to be treated with questionable preservatives or glues. Treated wood ends up as toxic waste and cannot be returned into the natural cycle to turn into valuable mulch and nutrients for other plants. It also cannot easily be burned either. This toxic waste is the beginning of a dead end road.
How can you afford to leave this kind of capital lying around for such a long period?
From a business point of view this might seem right. However it doesn't have anything to do with using wood in the most ideal way.
The purely technical way of drying wood fast, unfortunately misses out on all the subtle benefits of working with nature.
Some economic experts who visited our saw mill showed utter disbelief when they saw a stack of oak boards which had been drying for four years. These boards were to be used for a solid wood floor at some stage. Four years of tying down capital when everyone knows you might as well kiln dry it in just a few days or weeks.
In those years of storage and slow drying, something else and as important is happening: oxidation and several other processes cause the breakdown of nutrients for insects and fungi. This natural process to preserve wood is not happening when speeding up the drying process with a kiln (which takes from a few days to weeks).
A stack of sawn boards which has been stored outside for a few years (protected from water), has been exposed to hot summer days as well as freezing winter nights. These boards have not only dried, they also experienced and adapted to the different weather conditions. This 'memory' has a relaxing effect on the wood.
The rule to remember is: The faster the wood is drying, the more it will warp and twist. This is called the sponge effect. It means that on humid summer days, this type of wood absorbs more moisture from the surrounding air, expands ad works harder than wood which has dried naturally over some years.
However, wood used for building and furniture manufacture has shorter drying and storage times than the highest quality wood used to build instruments. Depending on the type of tree and intended use, one to three years of air drying are sufficient here.
The ability of wood to absorb and release moisture can be compared to a sponge. Timber which has been stored for a long time matures and dries slowly. It stays in shape even when the humidity is fluctuating, whereas younger and kiln dried wood tends to warp and bend. This principle always applies.
Dry Rot and Wood Rot
The water in a living being like a tree is more than just content in a tank which can be filled or emptied. The example with the oboes shows that at the end, kiln dried wood contains the same amount of moisture as wood which has been dried for 30 years. However, oboes made from kiln dried wood crack whereas seasoned wood doesn't, it stays stable and resonates.
After a short time, the sap started to drop from both stems, however the piece lying downhill with the tree top lost three times as much sap than the other one, which had the bottom part of the tree pointing downhill. This is not surprising and confirmed our expectation. This ideal way of drying wood naturally results in a better quality product.
I cut the trunk into two pieces and had both pieces pointing down a hill side; one piece was lying with the tree top pointing downhill and the other piece with the bottom of the trunk pointing downhill.
When the tree top points downhill (right), the trunk loses moisture faster than the one on the left.
The sap moves through the channel and pipe system from the trunk into the branches to grow leaves and flowers. When the tree is lying tree top downhill, gravity too supports the flow, naturally drains the sap and the trunk dries evenly.
We wanted to test this and undertook the following experiment: One spring, when the trees were growing leaves and the sap was moving freely, I cut down a beech tree.
Tree Top Pointing Downhill and the Forces of Nature
The old wood workers say: "If you want quality building wood, the best way is to cut the trees and have them lying with their tops pointing downhill for a few weeks before you cut off the branches."
When a tree is cut down, it wants to procreate one more time.
Trees or fresh logs contain large amounts of water often weighing more than 50% of the trees' weight. Every piece of wood, no matter if it has been used for furniture, roof trusses, toys or building, contains only a fraction, approx. 6-20% moisture content.
In the following chapter you will read about the other requirements you need to consider to produce high quality building wood.
This natural resistance is the basis of wood preservation without toxic chemicals and the secret behind the durability of wood buildings which have survived hundreds and sometimes thousands of years without damage. 'Natural wood protection' means to harvest the trees at the right time and dry it in ways which further protects it from insects and fungi.
How Much Moisture is Appropriate?
It is not only the growth of the tree which depends on water. The moisture content attracts fungi and insects which potentially cause damage to wooden buildings and artifacts.
The question is how much moisture is left in the wood? Below 20% moisture content, wood is protected from fungi and below 8-12% from insects.
I don't play the oboe and I can't proof this musician's story, but it made me ponder anyway. I am thinking about the wood stacks which have been stored for years in our mill and remember business experts calling it 'dormant capital'.
However, the point is, when it comes to making the best instruments, slow and naturally dried wood cannot be produced by any modern kiln.
New techniques like pressure treating wood with hot oil are being used to manufacture wood instruments. The Musician's comment was that these instruments look nice - and are not as prone to cracks, however their tone is different. Even though they are manufactured very well, they are only suitable for beginners and school purposes, not for the use in orchestras. "This wood just doesn't sound right anymore."
Oboes and clarinets are manufactured from black Ebony. Traditionally professional instrument makers used to store Ebony for 20 and up to 30 years before using it to build fine musical instruments.
In recent years the demand in Europe for these instruments rose steadily. This means that nowadays, there hardly is any oboe made of wood which has been dried and stored for that length of time.
Musical Instruments and Moisture
The following story shows the importance of the moisture content or humidity levels on the drying process of wood.
An oboe player, who has become famous in Claudio Abbados' Youth Orchestra and works for several European concert and opera houses, has told me about his observations:
Once you want to know where the wood came from, the seller will ask his supplier. Soon the saw mill and forester will be confronted and this will cause them to start sorting their wood accordingly. The end result of all these efforts will be buildings, toys, furniture and other wooden items free of chemicals and toxins.
We and the next generation need to take this opportunity to build a healthier and more sustainable lifestyle.
I gleaned these insights from my experience of processing many thousands of trees from the forest to the finished item. The formula is always the same: observe nature and act accordingly.
To consider the origin of the wood is not only relevant to the forest owner or other wood professionals but also to the end consumer.
A spruce grown in unnatural circumstances is inferior in quality and less durable compared to one which grew in its natural environment and conditions.
Taking this a step further, I would not use wood from monocultures in low-lying areas for a job like a winter garden or glass facade. The demands on the frame are high and the wood must be stable and calm.
Due to Holz100 technology, even large projects like hotels can be built with solid wood. Holz100 offers fire safety sound insulation, security and comfort at a level unmatched by normal building methods.
If one compares the end product of wood grown in its natural environment with wood grown in a monoculture, one can see the qualitative difference.
Holz100 Canada Inc.