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Your Instrument’s Grain: Quarter cut or Slab?
Inside-the-Shop are informative articles
written by Kevin Smith, Luthier of The Violin Shop
Your Instrument's Grain: Quarter cut or Slab?
Standing on a mountainside near Klamath Falls in Southern Oregon, I looked up from the base of an Englman Spruce tree and almost fell over backward: 130 feet of standing spruce that took 3 of us fingertip to fingertip to reach around. There were cellos in that tree. Victor Gardner, our guide and mentor, had brought us there. And as any truly great guide does, he educated us about the trees we sought.
First we looked for trees without limbs in the lower 20-30 feet. If it was clear of branches and knots it was a good candidate for violin making. He showed us how to look at a dried twig hanging from a branch to determine if the tree would split straight or with a twist. Simply look at how the air cracks formed as it dried: if the cracks are straight, the tree will split straight. If they crack with a twist, the whole tree will have the same twist. If there isn’t a branch hanging low enough to look at it’s dried twigs, you find a crease in the tree and observe the same thing.
Once a tree had passed this far, out came the core sampler. A hand screw with a wide T shaped handle and a hollow bit about 30 inches long and ¼ inch or so in diameter. Victor would tap the tree, pulling out a long cylinder of spruce. You need to check for wood rot, bug damage, grain pattern and density.
So we followed Victor through the woods for a full day while he let us find our trees in a target rich environment.
And that’s how I found myself at the foot of that enormous tree with a chainsaw in my hands. I’d just cut out a wedge half way through the tree and stepped away. Victor raised his freshly honed double bitted ax and sunk it deep into the cut. I’d asked him to show me how to cut a dutchman. It’s a trick cut to make a tree to fall in a different direction than it leans.
After he’d cut the dutchman, I made the final cut. Over the din of the chainsaw the tree let out a deep snap and shuddered. I pulled out my saw and stepped back about 20 feet.
The tree stood still for an eternity. Then another snap and shudder. A hundred and thirty feet up, the top swayed. A moment later the massive trunk let out a jolt of sound that went straight through me. And even though the trunk looked still, the top was moving in the direction I wanted. Unconsciously backing away, the sound exploded. We jumped as our sense of time splintered. And in the savage roar of thick timber ripping, shattering across 300 years of grain, it caught an unexpected treetop that changed the direction of its fall. Stripping the branches down one side of the obstructing tree for a hundred feet, the smell of pine resins from the trunk snapping in front of my face was so thick I could almost smell it with my skin. Through a cloud of splintering branches, this 130-foot tree weighing well over 10 tons hit the ground with the force of a small earthquake, bouncing back in the air with the flex and shimmy of a hooked trout. The butt of the trunk, 19 feet in circumference, swung 30 feet from my left to right in a blink, and finally landed, settling still and quiet.
The air thick with a cloud of debris, I was frozen. I stood in shock for almost 10 minutes. Finally Victor barked at me: “GET TO WORK!!” Stunned, I started moving again. But the memory is burned into my mind. A tree that was alive when Stradivari was just a kid. A huge, long life. It almost broke my heart. Fortunately, it was excellent wood.
We cut the tree into lengths of cellos, violas and violins. Standing the rounds on end we split them length-wise with splitting wedges and mauls (a combination of ax on one side and sledge hammer on the other). Looking from the top at the cross-section of the tree, the round had the shape of a cut pie. After removing the bark and sealing the ends in wax we loaded our trucks and 4-wheeled our treasure out of the mountains to season for 5 years.
Years later, when at last these billets of wood were ready to be made into instruments, you split or cut it length wise down the middle again, starting at the pie shaped end. Unfolding it, you have two identical halves. You join the thick edges and end up with a “roof-top” from which the arching's are carved.
And finally I get to the point of all this. The reason you cut it this way is so (when looking from the end) the grain will be as close to vertical on the top and back as possible. It’s called a “quarter cut” piece of wood. It’s cut that way for strength.
If you take your instrument and look at the end grain of the top and back (looking at the edge just to the side of your tail piece with the ribs facing you, or the edge by the side of the neck) it should be running more or less vertical. If it’s horizontal it’s a much weaker cut and is called a “slab cut”.
Slab cuts were common on backs at the beginning of the violin era around 1550. I’ve heard tell of tops that were cut on the slab from that time as well, but I’ve never seen one. I can’t imagine them lasting long in an orchestra pit. So as violin making evolved, quarter cut wood was the clear winner for both strength and sound. Particularly for violin, since quarter cut wood has a more forceful sound that will carry. A slab cut back on a cello or viola works well though, as slab cuts will have darker sound qualities, much like an alto or baritone.
In a future issue we’ll discuss the effect a “flamed” maple back has on sound, and the difference between the grain and the “flame”.
P. S. The evening after I cut down that tree, Victor walked past me, put his hand on my shoulder, and looking me in the eye said: “Kind of makes you sad, doesn’t it…” He knew. But my real consolation was knowing what that tree would become.
After the archings are carved out of that solid piece of spruce and maple, they need to be scooped out with a 30mm spoon gouge. This is called graduating. With calipers measuring the thickness, the dimensions are brought down to rough dimensions. From there, thickness are graduated with finger planes to within 1/10th of a millimeter. And finally smoothed out with steel scrapers.
Along the way you’re constantly feeling the flex of the plates, tapping them for clarity of tone, and adjusting the graduations to the inherent strength and density of the wood, it’s grain, and yes, to whether or not it’s slab or quarter cut.