American Black Walnut is the Craftman’s Darling
It’s dark, handsome, classy, and a downright joy to cut, shape, sand and finish into a wonderful project.
But there’s a downside.
It’s really easy to look at a pile of walnut and assume it’s low in quality because walnut, the poor guy, has a lot of characteristics that you don’t find in other woods. That means even the best grade of walnut comes with appearance flaws and defects.
Walnut is just different.
Building projects out of walnut means doing more cutting, arranging and flipping of your boards than you might be used to because it’s more varied in color and grain than most other woods. Part of the art of woodworking with walnut is in figuring out how to deal with, hide, or include knots and sapwood.
Here’s what to know and understand – and what you can do about it.
Sad but true: walnut trees grow with a significant number of branches, and branches create knots in lumber.
Depending on your taste, you’re going to find some knots acceptable and others objectionable because they can be:
- small or large
- cracked or solid
- loose or sound
- near the ends, edges or middle
- Knots are also the source of fascinating figure like curl, fiddleback, swirl, crotch or quilt
So where is the line drawn? With the lumber grade. Lumber grades establish what you can reasonably expect from the lumber. That includes 1). calculating the percentage of clear wood in a board using math, 2). defining the size of allowable defects.
The grade of lumber we usually sell is called “Select & Better,” which is a mix of the top 3 lumber grades money can buy.
Here’s a quick summary of Select & Better walnut (according the the NHLA Rulebook):
- Minimum 83% clear on the best side
- Knots 1-1/4″ in diameter are counted as one defect
- Both sides clear is never guaranteed
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All trees have a sapwood ring, which is the pale yellow-white section of wood between the bark and the heartwood. It’s the part that transports water and nutrients throughout the tree. Some species have a narrow sapwood ring, some have a large sapwood ring.
Walnut suffers on two fronts:
- The sap ring in walnut trees is pretty large
- The color variation really stands out because the heartwood is so much darker
Sapwood is allowed in all grades of walnut lumber, but with some limits. And, according to the rules, the face of a board must have less sapwood percentage than the back of a board.
We only buy walnut lumber that’s carries a specification of a minimum 80% heartwood on the best side. That means some boards in the pile could have more heartwood, but, regretfully, it’s not guaranteed.
Why 80%? It’s a matter of economics and supply. On rare occasions, some walnut suppliers do have a selection of walnut with a greater percentage of heartwood, like 90%+. It’s very expensive, and it’s not available all the time. If you think walnut is expensive, you should see the price of 100% heartwood walnut.
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Walnut Lumber Is Steamed
What and why? Steaming is how the walnut lumber suppliers do what they can to fix the color disparity between heartwood and sapwood.
The concept is that steaming evens out the color, reducing the contrast between heartwood and sapwood. In non-steamed walnut the line between sap and heart is quite sharp and abrupt. In steamed material, it’s more graduated.
How do they do it? The lumber is stacked face to back, and loaded into a steaming chamber. Steam is fed into the chamber for just a couple of days, and then the lumber is left to cool down in the chamber. Then the lumber air-dries until it’s ready to be dried in a kiln.
The downside is that steamed lumber, after planing, generally has a grayish brown color devoid of the nuanced deep purples, browns and yellows you’d find in raw unsteamed material. To be fair, steamed walnut color jumps to life when it’s finished. Plus, all walnut lightens up over the years with exposure to UV light weather it’s steamed or not, and changes to a dark golden amber (unless the project is stained or dyed). So in the long run, there may not be a distinct advantage to using unsteamed walnut in a project – other than for the romance of working with it.
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Here’s What You Can Do
Expect a Waste Factor
This means you need to plan to have enough lumber to flip boards and arrange grain in a way that’s pleasing to you.
Work with Knots
Don’t be too put off by knots. First of all, if you run into one you don’t like, flip the board to find out what’s on the back side. Good chance you can just hide it on an unseen part of your project. Otherwise, you might be surprised at how well knots can blend in when filled with a dark filler. Plus knots have a charisma and grace that only wood can provide.
The best, clearest, straightest walnut logs get turned into veneer, not lumber. It’s a matter of economics: veneer manufacturers pay a lot more for logs than lumber producers do, therefore they get the better ones. So if you absolutely need walnut that’s evenly colored, free of knots (even tiny ones), you need to use veneer.
Finish for Color
Oil based finishes enhance the dark heartwood very easily.
You can also improve the natural contrast in the wood by using a dark-tinted Danish oil, or applying a dark (but thin) oil stain, or glazing over a clear sealer, or filling the grain with a dark brown filler. Basically, anything dark that locks into the open grain of walnut will pop the grain nicely.
To control the color, a finishing recipe over the entire project of an orange-brown dye, clear sealer, and a glaze with a dark brown oil based gel stain does a marvelous job of blending sapwood, enhancing the wood’s dark grain contrast, and giving it a color that will last for years and years.
Otherwise, check out our tutorials:
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Vice President of Operations – Woodworkers Source
We’re a family-owned lumber & woodworking supply retailer with 3 delightful stores in Arizona, and 35 friendly employees.
Mark oversees the company and creates tutorials on wood finishing and woodworking tips for hardwood lumber.
Woodworkers Source is a division of MacBeath Hardwood Co.