Saturday, January 12, 2008

That special wood

One of the most distinguishing characteristics of Arts and Crafts furniture is the use of quartersawn white oak, apart from the practical aspects, its strength, stability and color, the flakes caused by the medular rays not up taking stain as readily as the open grain gives the furniture a striking appearance. The use of oak for furniture goes as far back as furniture itself, the wood is exceptionally strong, and resistant to decay. Stickley writes in the Craftsman

Gustav Stickley (ed.) / The craftsman(July 1909)
Our native woods and the Craftsman method of finishing them, pp. 428-436
There are many varieties of oak in this country, but of these the white oak is by far the most desirable, both for cabinetmaking and for interior woodwork. One reason for this is the deep, ripened color it takes on under the process we use for finishing it,-a process which gives the appearance of age and mellowness without in anyway altering the character of the wood. There is no question as to the greater durability of quarter-sawn oak for uses which demand hard wear and also where the finer effects are desired, as in furniture. The distinguishing characteristic of quarter-sawn oak is the presence of the glassy rays, technically called medullary rays, which bind the perpendicular fibers together and give the oak tree its amazing strength. In quarter-sawing, the cut is made parallel with these medullary rays instead of across them, as is done in straight sawing, so that they show prominently, forming the peculiar wavy lines that distinguish quarter-sawn oak. The preservation of the binding properties of these rays gives remarkable structural strength to the wood, which is much less liable to crack, check or warp than when it is plain-sawn.

Now lets get into the details. What does it mean to Quartersaw? The photo on the left shows an example. When lumber is plainsawn, flat slabs are cut all the way through the log. When it is Quartersawn the log is cut into quarters, then a board is cut off, the quarter is turned 90 degrees and another board is cut, this process is repeated until there is not enough left to cut. However, only the first few boards to come off the log are truly considered quartersawn, that is, the growth rings are from 90-60 degrees from the face of the board, from 60-0 degrees from the face is considered to be rift sawn and while still very stable, does not exhibit the same degree of flake as quartersawn lumber. As you can see this leads to less wide boards, less yield per log, and is labor intensive. This explains why quartersawn white oak is more expensive then plainsawn white oak. In the example above, boards 1, 2, 3 and A, B, C are quartersawn, 4, 5, D, and E are rift sawn and 6 is waste.

What you end with is a board with tight growth rings perpendicular to the face, the medular rays visible as broad light colored flakes. This board is very stable with little tendency to swell or cup. The tight grain takes in stain or dye very deeply whereas the flakes do not. This contrast is enhanced by the methods we use to color it, ironically, this contrast was considered less than desirable by the original makers of arts and crafts furniture and the methods they used to color their furniture de-emphasised the flakes.

If you look closely at the picture to the left you will see the medular rays as light lines radiating from the center of the section towards the outside. When the tree is alive these rays are a transport system to bring water and nutrients from the core to the new growth. You can also tell that by cutting the boards with the rings perpendicular the rays will be shown as a flake on the finished board. You can also see the lighter sapwood near the bark and the darker, denser heart wood.

As a woodworker not only do you need to learn skills and techniques, but you need to learn about the medium you are working in. A working knowledge of wood, its characteristics and properties will make your projects a step better. If you were to build a perfect replica of a Stickley Morris chair, with tight mortises and perfect tenons yet used plainsawn red oak the result would be disappointing. Even when you use the correct wood, you still must take the time to pick the best piece of wood with the right grain for each part of your project. For a Morris Chair, I pick the best pieces with the grain for the arms as this is the most visible feature. I hope that this post has shed some light on this subject and that you are enjoying this blog.


Anonymous said...

Thank you very much.

This is the best explanation of Quarter-sawing I've found.


Anonymous said...

Thank you for shairing your knowlege with us. A great discription of quarter sawn oak with nice photos.