Canadian Woodworking

Medullary Rays

Author: Peter Mac Sween
Photos: Rob Brown
Published: April May 2022

One of the most common characteristics of the Arts and Crafts Movement is the strong visual of medullary rays in white oak. Learn what medullary rays are and how you can make the most of their striking look to create eye-catching furniture.

The Arts and Crafts Movement emerged in England during the mid 1800s. It was built on a philosophy that opposed industrialization and emphasized the importance of craft­manship. These principles soon reached North America where famed furniture maker Gustav Stickley and others built on the Arts and Crafts style by adding a unique North American per­spective called Mission Style.

Furniture crafted from these concepts emphasized simple rectilin­ear designs. The mortice and tenon joint was a prominent feature and it was often exposed to show the skill of the craftsman. The use of exotic woods with fancy figures and other visual ornamentation was discouraged. Arts and Crafts makers wanted to construct sim­ple, well-made furniture for all people.

White oak was the wood of choice for the Arts and Crafts move­ment, both here and abroad. It was locally available, strong and sturdy. When quarter sawn, vertical grain is revealed, which com­plemented the linear design elements. Quartered white oak lumber also shows the silver flake figure. This figure, which is found in all white oak trees, added an interesting visual character on the lumber faces.

What are the specific structural features of the white oak that visually influenced the Arts and Crafts Movement?

Red Oak End Grain
You can see the long, more pronounced rays in the end grain of this piece of 8/4 red oak. Red oak has pronounced rays, but white oak’s rays are wider and more pronounced, especially when the face grain is viewed. Notice how only one face of this board will showcase the rays, as the other face is too far from being perfectly quarter cut.

Red Oak End Grain

Leopardwood
One of the most pronounced ray presentations in the world can be found in leopardwood. It provides a very strong visual when cut and used carefully. This sample is veneer, which is usually cut from the best quality trees. (Photo by Ella Mac Sween)

Leopardwood

Rays in Maple
This radial face of maple shows small rays. Although the rays in maple aren’t as visible as in oak, they provide an almost shiny look.

Rays in Maple

Quarter sawn material

The flake figure is always present in the wood of the white oak. It is only revealed by the maker when the wood is cut or sliced on the quarter. This makes the figure a consistent part of the beauty of the wood and also reveals the work of the craftsmen which fits the Arts and Crafts philosophy.

The flake figure is produced by the medullary rays of the tree. The medullary rays are made up of specialized cells organized in a radial direction from the pith of the tree to its circumference similar to spokes on a wheel. Functionally, they serve the tree by moving nutrients between growth rings. They also store sugars for the tree in the winter months.

Medullary cells are present in all trees. In the softwoods they are microscopic, not seen by the unaided eye. In the hardwoods they show a wide diversity in size. The rays in basswood are very small and are inconsequential visually. Ray cells are often stacked verti­cally and can form large bands of tissue in the wood. These cells are largest in the white oaks where they can reach 4″ in height.

Since the medullary rays are orientated radially, they are fully exposed when quarter cut or sliced. The size of the medullary rays is maximized in this orientation with the growth rings perpendicu­lar to the sawn or sliced face. As we move away from 90°, the rays will progressively change in shape and get smaller in size. When we reach the flat sawn or tangential surface, the medullary rays present as small, thin greyish vertical lines.

While white oak was the choice for the Arts and Crafts makers, there are other species with outstanding medullary rays. Those of the Australian lacewood produce the namesake lace-like pattern of small “buttons.” This figure shows best with material cut slightly off of 90°. Leopardwood from South America shows a similar pattern.

There are some notable North American species as well. Domestic sycamore, when quartered, produces a ray figure that reminds me of snakeskin. Quartered hard maple has small medul­lary rays, but when they are grouped together they can result in a metallic shimmer. Similar figure appears in quartered black cherry and quartered beech.

Working with medullary rays

I can’t emphasize enough the importance of taking your time when selecting quartered material for ray flake. Examining the end grain will allow you to pick the boards that are sawn the closest to 90°. Most mills call everything sawed with growth rings between 60° and 90° from the face quartered. As a result, you will be pre­sented with a wide range of flake sizes to choose from. Check both ends of the board. Trees rarely grow straight, and the ray pattern can change from one end to the other.

Quartered woods are small in size. Chances are that at some point you will have to glue up several boards to make up a larger piece. Most lumber dealers will have a mixture of boards from dif­ferent trees, and they will have a different colouration. Bring a block plane to allow you to assess the colour of a board by planing off some of the board’s rough surface.

Medullary rays also affect how lumber dries. The rays inhibit the shrinkage of the wood and also act as planes of weakness. Quarter sawn woods can show internal honeycombing as a result during the drying process. Quarter sawn wood also dries more slowly and less predictably than flat sawn material. Combine the two and a stack of quarter sawn material will have a fair bit of warped wood. Choose your lumber carefully to avoid a high waste factor.

One face per board

Since the rays are a radial phenomenon, the ray flake will show up only on opposite faces of a board. If you want to see flake on all four sides of a chair leg, for example, you will have to get creative. One method is to glue veneer on the edges which show little flake. You could also mill up four pieces and glue them up using a lock miter joint. Check out Issue 130 of CW&HI for some tips and ideas regard­ing the use of lock miters.

The best examples of flake figure will show up in veneer. Veneer logs are of a higher quality than saw logs, so the veneer mills start with an advantage. The process by which veneer is manu­factured allows us to precisely control the angle the log is sliced at. Quartered veneer is as close to 90° from the growth rings as you can get. While not common in the Arts and Crafts move­ment, veneering is an appropriate technique when working large surfaces.

Bookmatching can be a challenge when dealing with flake. While ribbons of flake can be large, they are also thin. If you are resaw­ing to bookmatch, you can easily lose some flake in the kerf of the saw cut. All is not lost, though. The basic vertical grain of the back­ground will be there. Just be prepared to see flakes popping into and out of view on either side of the bookmatch.

Choosing a finish

Since the flakes present as a slight depression on the surface, they will have to be filled if you want a glass-like surface. However, the filler can obscure the flake, giving it a plastic-like look. I agree with the approach taken by the original Arts and Crafts makers. A stain to emphasize the rays followed by either an oil or very light film finish is a good approach to follow.

Working with ray figure should not only be considered an exercise in reviving the Arts and Crafts movement. Ray figure can visually enhance many contemporary furniture pieces, as well. One of the legacies of the Arts and Crafts movement is to respect the materials you work with. Learning the techniques of working with what the wood gives you will help make your woodworking journey an even more enjoyable one.


Peter MacSween - [email protected]

Peter's woodworking journey began with a career in carpentry followed by a decade buying and selling veneer. His spare time is spent abusing his guitars and exploring the great outdoors.

Leave a Reply

Your email address will not be published.

Other articles