Knowledge of raw materials, equipment, care in manufacturing gives our clients quality products!
The following comes from a presentation by our own Ken Koleszar-IOW Operations.
Hardwoods are produced by angiosperm trees that reproduce by flowers, and have broad leaves. Many species are deciduous, meaning they lose their leaves in the fall. Softwood is a wood from gymnosperm trees such as pines and spruces. Softwoods are not necessarily softer than hardwoods. In both groups, there is an enormous variation in actual wood hardness, the range of density in hardwoods completely including that of softwoods. Some hardwoods (e.g. balsa) are softer than most softwoods, while the hardest hardwoods are much harder than any softwood. The woods of long-leaf pine, Douglas fir, and yew are much harder in the mechanical sense than several hardwoods. Softwoods are mainly used in the construction industry, whereas, hardwoods are used in furniture making, flooring etc. The main difference between them is that hardwoods are porous whereas, softwoods are not. In fact, Red Oak is so porous that you can blow bubbles through a three- or four-inch piece of it!
American hardwoods are some of the most desired in the world for furniture making. There are many reasons for this. We have large forest that can sustain the need while reproducing for future needs. Many have beautiful figure that can give a three-dimensional look such as Curly Maple, also known as tiger maple, or fiddle back maple since it is used as a tone wood in the making of string instruments. This striping can happen in most any hardwood species but most commonly occurs in the Acer family of trees, such as maples and birches. In birch, the stripes are further apart and is known as Flame Birch. Only 5% of trees are curly. Instead of the grain growing straight in the tree, it grows in a sign wave. The striping or curl is exposed when the saw cuts across the sign wave exposing the peaks and valleys. A tree can be curly all the way through, but usually toward the outer edges. One side may be curly and the other not. Bird’s eye Maple has small circular patterns that are the start or buds of branches that never fully formed Quilted figure is only found in the Western Big Leaf species of maple and can look like boiling water. Figure comes about usually in one of two ways. I can be due to the way the grain grows, such as those listed above or by the way the log is cut to expose rays, as in quarter sawn Oak and Sycamore.
Another interesting aspect that can occur in lumber is spalting. Spalting is the start of the decomposition process. It appears as black lines in the lumber and are the front line in a war between two equal strength fungi competing for the “food” or recourses of the wood itself. One will throw up the black line to stop the progress of the other. It’s kind of like putting up a fence. After a time, the decomposition process must be halted by drying the wood out before it starts to rot. If stopped at the correct time, the wood will have lost little to none of its strength, yet still have the spalting,
Hardwood lumber’s thickness is measured in quarters. So, if you wanted a board a full inch thick, you would ask for a 4/4 (four quarter) board. A board 2” thick would be referred to as an 8/4 board and so on. Lumber can be milled with a circular mill or a bandsaw mill. Bandsaw mills are now the preferred method of sawing, since the blade is much thinner, the sawyer can obtain 30% more material per log. Smaller bandsaw mills can be obtained for only a few thousand dollars. They produce at a slower rate and will require more physical work than the larger mills but give the regular person the capability to mill their own material. Some other options are the Alaskan Mill which is basically just a jig used to hold a chainsaw horizontally while the operator pushes it through. This method works best with a skip tooth chain, since you are cutting with the grain as opposed to across. It also requires a large engine. 100 cc or more is best. There is a large loss of material due to the large kerf and requires a lot of physical work but there are also advantages. The whole setup can be carried into the woods. The log can be milled right where it is fell/fallen, and the boards can then be carried out. Before curing, the ends of the boards should be sealed to help reduce cracking. Cracking and checking occur due to the uneven drying of the material.
Once the material has been milled, it will need to be cured. This process starts with the boards being stickered on a flat surface. A series of sticks are placed perpendicular to the boards. A board is placed on the stickers, then another series of stickers is placed directly over the last and so on until all the lumber has been stacked. This allows air circulation for the curing or drying process. Once the material has been “stickered” it will need to be cured.
Curing can be done one of three main ways, each having different advantages. Most people have heard of kiln dried lumber. It has been used as a marketing catch phrase for lumber. The lumber industry has used it to convey a sense of quality: however, this is not necessarily the case. Kiln drying accelerates the drying rate by adding heat, for faster turnaround. The accelerated drying rate produces stresses within the material that can later be realized by the craftsman, when cutting the material. When these stresses are relieved, through the cutting process, the board will open at the cut or more dangerously pinch in on the blade, possibly causing an accident. Kiln drying can also produce boards that are case hardened. Meaning that only the outer portions on the board are dry, while the center remains green (moisture laden).
Another much lesser known method is vacuum drying. This is where lumber is placed in a large cylinder that can be closed air tight and a vacuum applied. These kilns can be the fastest to dry and most efficient with energy usage. In a vacuum, water boils at a lower temperature, so it evaporates at a quicker rate. Lastly, there is good old air drying.
As with most things, you can do it the fast, expensive way (kiln or vacuum drying) or the slow cheap way. The material just needs to be stickered and have something over it to keep off the rain. It takes approximately one year for each inch of thickness to properly cure, depending on location. Air drying produces much less stress in the board and is one of the best methods for curing.
Once it is cured, wood will continue to expand and contract due to the humidity of the immediate environment. Because of this, material should be brought into the shop approximately one month before working to acclimate to the new environment. If you bring a board into the shop and don’t let it acclimate, it will warp after you have flattened it. It could be flat today and warped, cupped, or twisted the next. You need to let it do all the moving it’s going to do, before machining, for it to stay flat.
Depending on where a board came from, within a tree, it may have different characteristics than another board from the same tree. Looking at the end of a board you can see the annular growth rings. The closer to the center of the tree (pith) the board came from, the less stable and prone to warping it is. The more vertical the rings are on a board, the more stable it becomes. Again, depending on where in the tree a board came from, the grain pattern differs greatly. Using the right grain for the right purpose makes the difference between a utilitarian piece or a beautiful piece.
There are many finishes and stains on the market today. I will only discuss what is used on our products. First off, I NEVER use stains. If I want it to look like cherry, then I use cherry. As far as the finish, I use tung oil. It soaks into the wood, giving more depth to it than say a polyurethane, which just sits on top. Depending on the material, I apply usually three to four coats, sanding in between each. Lastly, I use steel wool and wax for the last coat to give a silky-smooth finish. Oil is softer than some other finishes, but scratches can easily be fixed by sanding and reoiling. Whereas polyurethane would need to have the whole piece striped and refinished.