First a disclaimer. I'm no expert on the subject, just my understanding of the science at work.
Oh, and I am an old fart... and tree do reveal secrets:-)
Ah the color and figure of a piece of wood! It is enough to send the heart of a woodworker racing and his forehead pearling with sweat... And then you go in La la Land thinking about what you could do with such a piece.
Why is that? This object of desire for a woodworker was never cheap! Lots of labour and time between the tree standing and the boards ready to be worked on at your bench.
Yet, to this day, many still hold the common piece of wood as being cheap!
As in: Ah, it should not cost much to build that out of wood, why so much??
Because it is not made of termite barf (OSB, MDF) being solid wood and constructed solidly (No Allen keys required), it should outlast us all... would be one reason
Even if using all "Free wood" there is a lot of time and experiences that goes behind building something out of "wood".
Never mind the cost of the specialized tools required and assorted supplies to be used
But there are no such thing as "Free wood", each steps between the cutting down of the tree until being finally worked on your bench are all going to affect somewhat the final product, in both form and function and of course, its price!
To this day, the most "Dramatic" operation, remains the sawing into lumber. That is where the sawyer can make or break a saw mill operation, by the decisions he take about were to cut into the lumber.
Maximise yield, or waste a lot. Yes, he was a valuable man, and the better paid in the whole crew.
You can often spot the sawyer in a group picture, by the way he is dress and were he stands, being the better paid man.
GOING BACK IN TIME
Trees are a part of the botanical family, they are a plant.
Some trees are among the oldest thing still living today on this earth. They have been around a long long time, and know a awful lot about what happened around them all these years..
Baobabs tree over 2000 years old and still youngsters to some.
A list of the oldest known trees Not all older trees have a large girth.
Where they grow, the climate encountered thru its living years and the ravages of Mother Nature: Strong gusting winds (produce shakes), growing on an incline (tension wood), flood (rot), forest fires (scars in tree rings) periods of draught (slow growth) etc. are all recorded inside the tree.
Similarly, the effects from man: Cutting or breaking branches, feeding it etc. are also being "recorded" inside the tree (knots, metal objects, tree rings anomalies, burning marks)
This Silver Birch had a severe lean, about 45 degrees, but was still reaching out for the sun.
The combination of yearly icy snow loads took a toll on it and how it grew.
That would results in a lot of stress built up in the tree trunk, just awaiting to get the unwary at the tablesaw. It is called reaction wood
The science behind all this is called
Dendrochronology, the science of the tree rings and dating.
Knowing how the tree rings are formed, yearly, seeing the rate of growth (the demarcation between the Early wood (Spring) and Late wood (Fall)) enable us to count the number of years contained inside the tree. Because most trees around the same geographical region are impacted the same by the local weather conditions, by comparing the rate of growth in the rings to other local specimens help
dating a piece of wood and establish its likely provenance.
Pretty cool heh!
This is possible because most trees have a definite differences between the early wood and late wood
That difference is in the size and density of the cells caused by the various growth rates. In the Spring the new growth on the foliage and the warmer temperatures combined to produce rapid growth.
The spacing between the rings is large.
In order to grow in both girth and height, a tree need to be fed.
Trees are nourished by the photosynthesis taking place on the green foliage by the action of the sun.
It caused water molecules to be evaporated in the day time. This in turn is pulling up water and its nutrient found around the tree roots system, via capillary action.
Hint that is why you always water/nourish a tree at his root ball (drip line around the tree), not via the foliage.
The added growth layer around the tree girth happened more like a cone shaped than a true cylinder.
The tree is larger at the trunk and smallest at the top. Layers are piling cones over cones
That is what create the familiar cathedral figure in flat sawn lumber
Maple on top, Apple on the bottom.
Both pieces of wood are oriented the same, the top of the tree is to the left,
as indicated by the grain forming cathedrals
Looking at "end grain"
My bundle of straw representing wood cells. The various colors represent the growth rings
Due to its cellular nature wood can hold water in both the "straw" inside of cell (free water) and within the cell structure of the "straw" Bound water.
These swelling and shrinking cell walls are what causes wood movements.
Ice cream cones give us a better representation of the true shape of the outer layers being added on
Since they are more cone shape than a true cylinder
Not to scale obviously, but you get the idea
This rapid growth experienced in the spring leaves tell tales larger spacing between the rings.
Conversely, as the colder weather approaches in the fall, the Deciduous trees change the colors of their leaves then loose their foliage to slow down the growth activity. The tree is dormant for the winter, experiencing little new growth.
The tree rings are smaller and closer together, hence often darker.
Our North American Deciduous trees need to drop the level of sap in the colder weather, or they will suffer frost damages.
Deciduous trees drop their foliage, while evergreen keep theirs.
The pines in the background are about 80 + feet high.
The cluster of Silver Birch in the foreground are saplings
that grew around the tree trunk that was cut
Evergreen have "build-in antifreeze". Pine sap extract is Turpentine, a wood alcohol, hence do not need to go dormant as fast nor as long. But they still produced clearly defined yearly rings.
The combined number of early and late growth rings produced in a year.
Harder to see on a rough surface, but you can clearly see and count some of the rings.
The space between these darker rings represent one year of growth, since these darker's one happened every fall. You can clearly see that the growth was not even around the tree.
How much sun reached the tree on what side, is enough to record a difference in the growth pattern.
The center of the trees are darker since clogged with sap.
These being cut in June, they were saturated at the time they were cut down.
But the center, Heartwood, is naturally darker than the Sap wood on the outer layers of the tree.
That is because as the tree grows on the outwards layers, the inside one goes dead and clogged with sap residues, imparting a darker color. Very noticeable in Walnut.
Near Comox BC, late 90s
The dead wood inside, remains sounds for a long time imparting strength to the tree trunk.
But in some quick growing and long living wood like Western Red Cedar, the inside simply rot away
revealing a big hollow when cut
Of course, tropical forest Deciduous trees do not experience as much of a climate change, but they do go thru periods of dryness and wetness (monsoons) and produce yearly rings. Relatively few, such as Teak, have visible rings. The "invisible ones" can be still detected, but not by our mere eyes.
Looking at two species, domestic and exotic
This exotic wood, barely shows, but there are faint, hard to see rings
In contrast, this piece of American Walnut, shows strong late years rings.
There is about 10 years captured in this piece of wood, but which ten years??
Lets have a closer look, since we have the technology :-)
Again, both same pieces of wood, same orientation
Exotic (Honduras Mahogany??)
The darker ring is not well defined and hard to tell were it start and end??
American Black Walnut
The more defined blacker line is the late growth year.
Between it and the next one equal one year of growth
In both these high magnification snap shots, the small white lines, criss-crossing the darker lines are radial lines, radiating from the tree core. They give rise to the gleaming ray flecks on beech, depending how cut..
It is via these lines that the sap travel to feed the outer cambium layer
The big round openings dispersed throughout are resin ducts
Here is a view of the same two wood, showing theses ducts on the surface
Exotic
Walnut
These ducts are showing sap residues which has long crystallized.
They contains minerals and some woods have a high contains of silica,
which is murder on a sharp edge
These two views, from the end grain and the top face also shows why wood glued on end grain is weak as compared to long grain to long grain glue surfaces. All the holes on the end will soak up more stain (making end grain darker) and have lots of "holes" with no glue surface
AND WHY SHOULD WE CARE AS WOODWORKERS??
Because then you can tell a lot about a piece of wood in your hands...
What it would be best as in, which orientation, problems areas, expected stability, workability with hand or power tools, you name it!!
This piece of pine is standing up the way it was inside the tree.
Notice the whiter sap on the outer edge?
See anything wrong with this board??
Now look at the grain lines.
The LH side lines are almost horizontal, while they are almost vertical on The RH side.
That tell us that the LH side will experience more change in dimension than the RH side and the board would not take an even stain. Nor would it cup the same across the board (pun intended).
I would probably not use this board as is and certainly not as a drawer side
Identifying a piece of wood enables us to have a look at its
specifics characteristics
Besides its weight and beam strength, one of the most interest to us, are its dimensional stabilities.
That is to say, how much is it going to move in a given orientation with changes in humidity.
Wood is hygroscopic, it absorb and release water in order to achieved the same humidity level as its surroundings.
Knowing this we can account for wood movement and ensure a sound construction that will not self destruct.
This frame and panel door, I made with a cope and stick router bit set,
fail open at one corner.
I did not allowed enough clearances in the frame to allow for seasonal expansion.
The same reason why wooden drawers stick in their opening sometimes.
And ironically it would not had fail if my shop dehumidifier did not fail me first...
.
In case you wonder, I always stain my panel edges before putting them inside the frame.
It avoid tell tale whitish lines when the panel contract.
Armed with the knowledge of various wood species, you can select the better resistant woods for outside project, which orientation make then more stable (flatsawn versus quartersawn) and much more to better build long lasting projects.
Reading the grain directions let us anticipate with direction it will plane best without tearout.
Although I will admit that it is sometimes tricky, but you quickly find out while working it...
And this bring us to today, to my lovely pile of freshly milled lumber awaiting to dry before talking to me. Drying and storing wood, a subject for another day...
Bob, who has a busy Monday coming up
But first, were is the ice cream :-)
