Hidden Treasure

Hidden Treasure:
Tom Compton from English Woodlands Timber reveals some of the tell-tale signs that enable him to read what’s likely to be on the inside of a log prior to opening it up.

The art of buying logs to yield particular grain patterns and figure is a practice exercised through accumulated experience of sawing and observation over generations. Knowledge has been acquired that enables current round timber buyers to predict likely outcomes. At the buying and selling stage this is critical in the calculation of value or desirability of a log so that after all the processing the miller produces something desirable to the end user. Hardwood log values are high so for all concerned it’s commercially critical that these judgements are secure, but there’s no doubt with trees and logs there is no way to predict or ensure an outcome, only to give a reading of the potential in a given tree or log.
For each timber species a round timber buyer employs the visual ‘tells’ on a log to help determine the likely outcome. They are a cautious and particular breed. They will likely see things that a lay person may not recognise. Some might say that they’ll use any excuse to push the log price down but the best buyers actually bring confidence to the process, appreciating the potential in the raw material with a mind to how it will be transformed in conversion to its best use for boards that in turn will make beautiful pieces of furniture or joinery. As we all know, trees grow over many decades if not centuries and each species has its own individual physiology of radial rays and annual cell structure (the ring growth), which when sawn reveals the different and varied grain patterns we are familiar with, vibrant medullary ray in oak (Quercus robur) or detailed lacewood figure in London plane (Platanus hybrida), for example. The wood we use today is the embodiment of a lifetime’s growing followed by careful felling and processing of a tree.

A product of the environment
Growing trees are, to a degree, a product of their environment. They must withstand the natural pattern of the seasons: cold, hot, windy, dry conditions, physical and animal damage, insect defoliation, fungal attack. The quality of soil, microclimate, aspect, elevation, silvicultural management, etc. are all variables that will influence how trees grow. These variables then create a historic record within annual ring growth and grain texture that is only opened up when the tree is felled and sawn.
Before even looking at the log the buyer will/should have knowledge of the conditions of the trees growing that gives a baseline of likely qualities. For example, oak grown on light, free-draining soils in, say, the New Forest is far more likely to suffer from high grain tension and shake than those grown on the deep clays of Wealden Sussex. The same species of tree will respond differently to different conditions of growth in order to survive and ideally flourish. It’s undoubtedly healthy trees with favourable growing conditions and accompanying silvicultural management that flourish and become the best sort of logs for working with.
The most profound moments for me as a forester and sawmiller occur when converting old, large dimension timber and revealing the grain that has not seen the light of day for 200 or 300 years. We recently put an oak into stick following sawing and found a piece of metal buried deep near the heart. The tree was at least 250 years old and so was a mere youngster during the Napoleonic wars, perhaps it was planted in response to the strategic need to bolster our oak forests? 

Reading the grain
So what are the visual tells that give clues as to the figure and suitability of a log for sawing? Well, when viewing a log I run through a sequence of questions to answer that are essentially the same for each species initially, but then become species specific. How does the general shape of the log present? I’m looking for a cylindrical shape indicating strong apical growth. Grain? Here I look firstly to see if the grain goes straight up and down the log or if it twists around the circumference. If I find the latter it indicates there will be lots of cross grain in the boards and they’re unlikely to dry flat or stay flat when worked on by the maker no matter how may years seasoning we allow. It’s one of the first questions I ask because it can be a particular feature in our oak and sweet chestnut (Castanea sativa). If it’s a log already felled I then look closely at the butt end (i.e. the end closest to the ground). This is like a window into the history of the tree and what can be observed here reveals the biggest tells. First, I’m looking for a nice central heart with even, concentric rings, layer upon layer, right through to the sapwood, sapwood being the outer most layer. This reading to the heart of the tree will at the same time indicate the presence of shake or not. Shake is the sawmiller’s bete noire and although we can’t avoid it altogether we need to identify these structural ‘faults’ up front. Shake occurs along the radial rays (star shake) or annual rings (ring shakes). On conversions these logs typically result in boards literally separating as they come off the saw or later during air drying or kilning.
Shake has very loud tells so we have that to be thankful for. When looking at standing trees, one can often predict likely presence of shake in oak before the tree is felled through observation of calloused, over vertical wounds in the bark close to the base of a tree or the somewhat tight and tortured look of bark. Conversely, well growing oak will have healthy looking bark and a light brown colour between the fissures. The light brown is telling that the tree is growing so quickly that the new cambium has not yet weathered, so not a bad sign. Shake is a factor in oak and elm (Ulmus procera), star and ring, sweet chestnut, mostly ring but less so in ash (Fraxinus excelsior) and sycamore (Acer pseudoplatanus) so we’re quick to spot it when selecting and buying round timber for conversion.

Predicting colour
After checking for shake and overall shape, my attention turns to colour as the next consideration. As a timber merchant I need to keep in mind our customers’ varied requirements. This means for joinery timber one wants an even colour to make matching boards easy, but for more decorative purposes and for bespoke furniture making, colour variations are often what’s desired. So at this point, the only tell available is in the butt end. Colour is species dependent of course and there’s no one answer to faultless identification of colour but starting with oak or sweet chestnut the holy grail is for an even honey or perhaps slightly pinky colour. A couple of species I tend to seek out where I can are elm and walnut (Juglans regia). In both cases, the darker brown it is the better it is. Darker overall colouring in these two tends to reflect the potential depth, richness and strength in grain pattern. Ash is an interesting one because it has a couple of recurring colour variations. My ash preference is for either completely pale, white coloured ash right across the log or a wide, strong coloured heart, ideally with that tell-tale green tinge that will reveal itself as olive ash. In sycamore it has to be white all the way as it’s the creamy white sycamore that’s valued above any other factors, apart from ripple figure of course! The colouring of hardwood timbers are ultimately variable as they’re affected, primarily, by the minerals in the soil taken up by the growing tree but they reflect the beginnings of natural decay or reaction to fungal infection in the tree.
The dark colour of brown oak, for example, is caused by an infection of Fistulina hepatica. Catch the tree before the fungus has caused too much infection and you have the beautiful brown oak but leave it too long and you are, sadly, left with a pappy mess. 

Signs of good figure
Figure in timber is perhaps the hardest feature to find and predict. One of the best known wood grain features is the lovely and very desirable ripple that we find in sycamore and ash. The ‘tell’ for this can actually be felt under the bark as a series of small waves or ripples. Log buyers of these two species will often knock off small areas of bark to look for it. In oak and elm the well loved pippy or burry figuring is observed externally through the presence of intricate knotty clusters on the bark. They appear either lightly spread along the log, in dense gnarly patches or completely surrounding the tree as a burr. These indicators are signs more than they are rules. They don’t translate to light, medium or heavy pip as one might assume. With pip and burr one can never tell exactly what the figure will be until you get the log up on the saw. This is part of the excitement, and sometimes disappointment, of milling hardwoods. Speaking of the saw, we can’t discount this important tool as a determinant of grain. Judicial use of the sawmill follows the careful round timber buying in maximising the potential of the logs. How one saws a log will determine and reveal different and desired grain characteristics. Often the most interesting grains are revealed when the radial rays are cut along their length. Such grain patterns don’t appear in the outer crown boards, not because they aren’t there but because the grain orientation off the saw is different.
I’m afraid I haven’t exhausted my knowledge here in this explanation but I hope I’ve gone some way to explain the process of selecting logs for their potential as useful, desirable wood that is fit for purpose. It’s just a taste of the diverse variables we find in hardwoods that makers and designers are seeking more and more. We are thrilled to have customers who embrace this diversity and who value the richness in the myriad of qualities that our native hardwoods provide. It certainly makes our job more enjoyable and long may it continue.