Walnut is a beautiful and unique wood. People love the natural dark chocolate brown color. Walnut’s color is super desirable, and people are willing to pay a premium price for it. If you’ve looked into purchasing walnut, you might have notice places specifying steamed and unsteamed walnut. In this blog, we go over the steaming process and how it affects walnut lumber.

Why is Walnut Steamed?

Walnut is desired for its heartwood, and the sapwood is considered a defect. So, walnut is steamed to darken the sapwood’s color, minimizing the contrast between the sapwood and heartwood. This also creates a more uniform heartwood color, removing any purple or olive green streaking.

What is the Steaming Process?

Steaming walnut is pretty simple. The green lumber is dead piled, or tight-packed, and placed in the steaming chamber. The steamer is usually set between 185-212°F with 100% humidity for anywhere between 24-96 hours. After the lumber is adequately steamed, the sapwood is no longer white but has the same chocolate brown color as the heartwood. After steaming, the lumber gets stickered and dried in a kiln.

Some walnut is steamed better than others. In cases where steaming quality isn’t done well, the sapwood will have slightly changed color, but there’s still a difference between the sapwood and heartwood. In some cases, the sapwood will even turn gray rather than brown.

What’s the Science Behind the Steaming Process?

Well, the best answer is we don’t 100% know why steaming walnut turns the sapwood brown. There are a couple of different theories that exist, but the most widely accepted theory is steaming walnut lumber “bleeds” the dark heartwood color into the light sapwood.

Is Walnut the Only Specie that is Steamed?

Cherry is also occasionally steamed. It’s not steamed nearly as often as walnut, but the steaming process has the same effects. It bleeds the pinkish-red heartwood into the cream-colored sapwood. But it also slightly changes the color of the heartwood. Steaming cherry removes most of the pinkish tones and leaves you with a reddish colored heart. Many woodworkers prefer unsteamed cherry, and most suppliers only sell unsteamed cherry (usually color sorted at least 90% heartwood on the best face and 50% or 70% heartwood on the reverse face.) Most woodworkers cannot justify the extra expense for steamed cherry.

What are the Pros and Cons of Steamed Walnut?

Both steamed and unsteamed walnut have pros and cons. First, steamed walnut is more readily available, which also means it’s more economical. You also don’t have to deal with as much color contrast between the sapwood and heartwood with steamed walnut. The heartwood color is also more consistent. But steaming quality can vary significantly between suppliers.

Unsteamed walnut is usually desired for its vibrant, dark brown color and purple and olive green color streaking. Of course, you will have more waste from removing the sapwood, but some people are willing to pay for the extra material. Because steaming walnut is the industry standard, getting your hands on unsteamed walnut can be a challenge, and when you do find it, be ready to pay the price for it.

What are the Grading Rules for Steamed Walnut?

In unsteamed walnut, the sapwood is treated as a defect, and the lumber is graded with a color sort. When walnut is steamed, all the sapwood is treated as heartwood, regardless of steaming quality. This means that the sapwood in steamed walnut is NOT considered a defect.

The other thing to remember is walnut has its own grading rules. Walnut lumber naturally has a lot of character, so the grading rules allow for more knots and wane/bark in the upper grades.  Usually, a fair rule of thumb is if a board would usually grade 1 Common, it would grade at least Select and Better by walnut grading rules.

What does Fine Craftsman Lumber Sell?

For the most part, we usually sell FAS steamed walnut. We try to sort out all of our walnut based on steaming quality. We also try to color match all the walnut boards in an order.

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