This is the third post of an ongoing series about wood. Understanding its nature, the way it moves and changes, and the implications for designers. Check back every Wednesday for the next installment.
The first two posts are here:
» How Logs Are Turned Into Boards, Part 1: Plainsawn
» How Logs Are Turned Into Boards, Part 2: Quartersawn
What is Riftsawn?
As we mentioned in the previous post, there is confusion about what constitutes riftsawn versus quartersawn, and this entry will help clear it up for you.
To recap, a board is referred to as quartersawn when it is cut radially from a log. As you get further away from a radial cut on a log, the angle of the grain/tree rings will start to get further away from 90 degrees. And as that angle starts to become less and less perpendicular to the face of the board, the classification of the board goes from "quartersawn" to "riftsawn." These diagrams should make it clear:
"True quartersawn" means 90-degree, radial grain, but these days the "quartersawn" term has been sliding--it won't be unusual for you to spot a board labeled "quartersawn" where the grain angle is all the way down to 60 degrees. These two boards, for example, were listed by a supplier as quartersawn, even though we can see the angle of the grain seems to wander past that 60-degree boundary:
Endgrain Photo 1
A sawing diagram illustrates this more graphically. The drawing below left allows you to see how they're letting the modern-day definition of quartersawn slide a bit, while the sketch below right shows the ideal:
Riftsawn, then, is modernly used to refer to boards where the grain is between a 30- to 60-degree angle, like this:
Endgrain Photo 2
Now if you compare Endgrain Photo 1 with Endgrain Photo 2, you'll see the endgrain angles look identical. Yet the former is being sold as quartersawn, and the latter is being sold by a different supplier as riftsawn. This is why it's important for you to be able to distinguish different cuts with your own eyeballs, so you can spot issues like this.
Adding to the confusion even further, the term "quartersawn" is also used to refer to the modern-day process of cutting logs, whereby they are quartered, then continuously tipped back and forth between cuts. I know that sounds bewildering, but luckily for you, we've located a video that will handily clear this up in a visual way you can easily remember:
As shown in the video above, modern-day mills have figured out it is most efficient to pull multiple types of board cuts out of one log, yielding both quartersawn and riftsawn. In fact, and this gets a bit confusing, you can have all three cuts--that's plainsawn included--in one log.
"If cut a tree into boards by the time you get to middle there are two boards that are essentially quartersawn - the grain is perpendicular to the plane of the wood - and the boards on top and bottom would be riftsawn," says Josh Vogel, a wood artist and owner of Black Creek Mercantile and Trading. "If you were grading the lumber basically you receive two quartersawn boards, four riftsawn boards, and the rest would be plainsawn."
In a nutshell: If a board isn't plainsawn nor quartersawn, it's riftsawn. We don't often say this, but please ignore what a Google Image search will turn up for "riftsawn," or even what you'd read about it on Wikipedia; it will only confuse you, as many folks out there—including wood suppliers!—incorrectly transpose riftsawn and quartersawn. That's why it will be useful for you to learn to identify the three types of boards by sight, using the pictures we've provided in this series.
Why Use Riftsawn?
In terms of wood movement, riftsawn (as defined in this series of entries) is inferior to quartersawn--though not as bad as plainsawn--due to its angle of grain. For that reason, no one seeks out riftsawn for its stability, unless they don't have the money to cough up for the more expensive quartersawn. From a performance standpoint it is a middle ground; riftsawn boards are essentially a wood-processing byproduct of the quartersawing process, and it's a less-expensive alternative to quartersawn that people can live with.
What Does Riftsawn Look Like?
Aesthetically, the figure of riftsawn provides a middle ground between the visually busy face of a plainsawn board and the stark lines of a quartersawn board.
In fact, most of the wood you're going to see in your life that isn't plainsawn is going to be riftsawn. (Quartersawn only turns up in expensive stuff.) You'll recognize riftsawn right away because, absent the cathedral effect of a plainsawn board, it looks the most like what we think of as "wood":
We hope that this sheds some light on the process. In any case, by now you should easily be able to identify the difference between plainsawn, quartersawn and riftsawn by looking at a board's endgrain. For example, you should be able to look at this photo...
...and by examining end-grain, see that the bulk of these are riftsawn--but you'll also spot two boards that are quartersawn, which will provide the best stability.
This should come in handy if you select your own wood for a project, and learning to visually identify the different types should overcome any misuse of terminology by a seller (assuming you don't buy your lumber sight unseen!).
In the next entry, we'll give you an overview of why wood moves in the first place. With that knowledge handy, you'll better understand the techniques that designers and builders use to compensate for it.
Material Matters: Wood
An Introduction to Wood Species:
» Part 1: Properties & Terminology
» Part 2: Pine
» Part 3: Oak
» Part 4: Maple
» Part 5: Walnut
» Part 6: Cherry
» Part 7: Mahogany
» Part 8: Rosewood
» Part 9: Ebony
» Part 10: Teak