First let me apologize for the delay in getting this week’s blog out. I’ve had a pretty busy few days. This week was the Chargers last pre-season game, so I was busy with that last night. I’ve included a few shots from the game at the end of this post for those that have asked about my photography work.
On with the wood.
Perhaps the least most anticipated thing about my taking this class was the fact that there would be days that we would spend the entire 8-hours of class listening to lectures. This week’s class was one of those days, but it was anything but boring.
Today’s lecture was dedicated to wood technology. I never realized there was so much to know about the medium. Of course I had taken the obligatory biology classes in college, but never really thought in depth about how a tree grows, and how that growth impacts how a piece of finished lumber will look.
I realize that the majority of readers here are experienced Lumberjocks and probably have a pretty good handle on what I was introduced to this week. With that said, I will highlight the parts of the lecture that I found most interesting and/or the topics that will guide some of the decisions that I make when selecting the stock for my project.
The thing that stuck in my mind the most was the fact that growth factors affecting trees are significant in determining how a piece of wood looks and feels. For instance, a piece of Maple from the Midwest would be different from a piece of Maple grown in a different geographical location. What I gathered was that the biggest cause of this is the amount of time the tree stays in certain stages of growth over a year period. Primarily this is caused by weather conditions. For example: A tree in Wisconsin will endure a much longer dormant state due to longer winters, where as a tree in say California will continue to grow for a longer period of time, this changes the early year and late year wood growth patterns, thus affecting the appearance of the lumber extracted from the tree.
Man has certainly influenced this process over the years as well. Early American settlers primarily constructed things from mature timber that was in abundance at the time. As the demand for lumber has grown, man has devised ways to have trees reach maturity at a much faster rate, in turn affecting the way the lumber presents itself.
Dave (my instructor) provided the below pieces of Douglas Fir to illustrate the point. Notice the growth rings on both pieces. While both sections are 2×4’s, the upper piece is from modern timber farming and grew at a much faster pace, making it less dense, lighter weight, and much softer than the piece cut from old growth trees. This really drove home the concept for me. Look and you will see that just this small piece has 100-years of growth rings …WOW!
We also covered how a piece of lumber is cut from the tree. I’ve seen this discussed here numerous times, so I will spare the details. Below is an example of a piece of flat sawn lumber (top), and a quarter sawn piece. What I learned is that not only does the quarter sawn lumber usually have a more desirable grain pattern, but it also results in less movement of the wood.
What is movement? I’m sure you all know this better than I, but here’s my shot at it. Lumber that has been dried has a certain level of moisture, say 6-8% for a Kiln dried piece, while an air dried piece might be 12-15%. With that in mind, if more or less moisture is introduced to that piece of lumber, the lumber will expand or contract accordingly. This causes movement in the wood, which can affect the structure of the lumber, and anything you have constructed from it. Common things that can happen are bowing, cupping, crooking, etc.
The Wood Whisperer has a great video that explains the process.
We also covered various defects in wood and how that can be a good or bad thing. Below are several examples.
Needless to say, I know much more about how to analysis a piece of wood than I did three days ago. This information will come in handy over the next week or so when I pick the lumber for my project. Just for fun, I made a dry run through three local hardwood stores today to get a feel of how they were laid out, and how to find what I was looking for. There are some incredible species of wood out there. Hopefully one day I will possess the skills to turn that raw stock into works of art.
I realize that this post is far from being a complete guide to lumber; hopefully others will fill in the gaps, and share their expertise on this subject. In particular, I would be interested in hearing about any internet resources that categorize lumber by its density, grain structure, etc.
Till next week.
All images Copyright 2007 Wayne Short, All rights reserved.
-- Wayne - Newbie looking to learn!