Wednesday, Woody Wednesday – What’s Up with Maple?

Every good blogger should have their schtick – something that they do better than anyone else to differentiate themselves from the crowd. I’m not a good blogger, but in my ongoing quest to pretend to be one, I’ve decided to leverage my wood properties skills as an ongoing feature. Surely that will catapult me to the big-time, right? Everyone loves wood properties. Thus, without further ado (and with apologies to Bono) I hereby decree that Wednesdays shall henceforth be designated “Wednesday, Woody Wednesday“.

My plan is to discuss a different wood-centric topic each Wednesday. Some days we might cover a specific wood property that is relevant to woodworking. Other days we might examine a particular species of wood in scrutinous detail. In any case, I hope to keep the posts interesting, useful, and super-geeky. (Yes, I did just use all three of those words together.)

What’s Up with Maple?

In our inaugural edition, we’re going to be talking about maple. Most woodworkers – at least, American woodworkers – will recognize only two varieties of maple: hard maple and soft maple. It’s a simple classification, but I’ll argue that it is not just overly simplistic, but flat-out wrong. I believe that there is value in knowing your maple down to the species, and I’ll do my best to prove why. Now, I’m aware that it probably isn’t possible if you’re simply buying boards in the form of lumber (unless you have a good sawyer), but it would certainly be prudent for any green woodworkers out there to make sure your dendrology skills are up to snuff.

So, what exactly are hard and soft maple? Let’s refer to a publication on the maple genus from the venerable Center for Wood Anatomy Research at the U.S. Forest Service:

The Maples can be separated into two groups based on the ray widths of their microscopic anatomy, the soft maple group and the hard maple group. Species within each group look alike microscopically.

Specifically, the microscopic difference between hard and soft maples is this: If you take a clean cross-section of end grain and examine it with a microscope or a 10x loupe, the rays of a soft maple will all be narrow and of uniform widths. If you examine a sample of hard maple, the rays will be of two different widths: some will be narrow, but some will be quite wide and prominent.

Get a clean cross-section of the end grain to see the difference between hard maple and soft maple. Click on the photo for a larger version. End grain photos are from http://www.wood-database.com

So what, exactly, does ray width have to do with the relative hardness or softness of the wood? Absolutely nothing. The terms “hard maple” and “soft maple” are American construct that were simply meant as a shorthand for differentiating the most common timber-sized maple species in the Eastern U.S. Referring to the same USFS publication, we see that they only classify five species, all of them native to the eastern U.S., as hard or soft maple:

The wood of sugar maple and black maple is known as hard maple; that of silver maple, red maple, and boxelder as soft maple.

And yes, in general, sugar maple and black maple are quite a bit harder than red maple, silver maple, or boxelder. But it’s a big world out there, and those five species are hardly the only ones out there (Wikipedia says there are about 128 maple species, in fact). The waters get considerably muddier once you venture out to western North America or across the pond to Eurasia.

We’ll only discuss eight species today, but they are the most common maple species that English-speaking folk (and therefore, people who are likely to be reading this blog) will encounter in lumber-sized trees.

Three additions to the aforementioned five are: 1) Norway maple, which has a huge native range that extends from Scandinavia eastward into Russia, and as far south as northern Iran. Norway maple is a familiar (and invasive) ornamental species in the northeastern U.S. 2) Sycamore maple, more likely familiar to the Brits as simply “sycamore”, although that’s confusing to Americans, since we refer to an entirely different genus as sycamore. Sycamore maple is native throughout Europe and naturalized in Great Britain. And 3) Bigleaf maple, which grows along the Pacific coast from the southern tip of Alaska to the Sierra Nevada of California. It is the only commercially important maple of the western U.S.

Okay, then. We have a list of important maple species and their corresponding wood properties¹. What should we care about? Well, since we’re talking about hard vs. soft maple, let’s start by ranking the species according to their hardness: 

Well, dang. It would appear that the “hard” vs. “soft” distinction is vindicated by this graph. Sugar maple is head-and-shoulders above the pack, a full 1200 Newtons (almost 25%) harder than black maple – the other hard maple. The soft maples (red, silver, and boxelder) comprise 3 of the bottom 4. But notice the degree of separation between red maple and its fellow soft maples. The gap between red maple and boxelder is as large as the gap between red maple and black maple. Red maple, along with the European species, seems to be in more of an intermediate territory between the hardest and softest maple species.

Now, hardness is all well and good. It’s the ultimate wood property of concern, if you’re building a bowling alley or a basketball court. But how many of us are actually doing that kind of work? For most woodworkers, hardness is a mixed blessing. Sure, sugar maple is less likely to dent, but it’s also much harder on your tools. What we as furniture makers (and particularly chairmakers) tend to be more concerned with is the strength of the wood – and that gets to the heart of my complaint with the whole “hard” vs. “soft” distinction. Hardness seems to get conflated with strength, but is that really appropriate?

Well, no. It isn’t. Let’s look at how these species rank with two common measures of strength: modulus of elasticity (MOE) and modulus of rupture (MOR) [here’s a link that includes an explanation of these properties if you need it].

 

Intersting, no? Yes, sugar maple is still the king of MOE, but look who’s sitting at number 2: red maple. Ahead of the European maples, and even slightly ahead of black maple. And what about MOR? The king has been displaced by a European interloper. Sugar maple sits somewhere between Norway maple and sycamore maple in ultimate breaking strength, and not far behind are red and black maple. Moreover, look how poorly silver maple and boxelder perform on both of these tests. Does it make any sense at all to include red maple in a group with these impostors? I would argue that it does not.

So, to wrap up my thoughts, let me just say that, from now on, I will be silently cringing any time a woodworker or wood peddler refers to their maple as “hard” or “soft”. (If you catch me on a bad day, there may be less silent cringing and more vocal argumentation.) Yes, it’s clear to me that sugar maple is superior – with regard to strength – to red maple, but does black maple deserve it’s lofty elevation, together with sugar maple, to be collectively referred to as the “hard maples”? Nope. Black maple is the equal of red maple, and not its superior. And red maple has certainly done nothing that is worthy of condemnation as a “soft” maple, together with boxelder and silver maple (both fine woods, mind you, but not stalwarts of strength and not to be confused/used as such).

I realize that I speak from a bit of a position of privilege here. I can readily identify any maple that I’m likely to encounter, and I process almost all of my own wood from tree to finished piece. Most woodworkers aren’t afforded that advantage. BUT, if you do have that option, then I would suggest you take advantage of it. Learn how to tell black maple from sugar maple, and red maple from silver maple². Not just by the leaves, but also by the bark. If you know what wood you’re using, you should be more confident in pushing it to its limits. And feel free to consider Norway maple or sycamore maple as a substitute for sugar maple. Those European species acquit themselves well when multiple properties are considered.

This is important to me is because, in my quest to find suitable substitutes for sugar maple for my Windsor chair legs, I’ve been forced to turn over every rock and examine every option. I’m satisfied at this point that red maple is a credible substitute, so I decided to give it a spin. More on that in this post from earlier today.

Footnotes

1. Wood property data comes mostly from The USFS Wood Properties Handbook. Data that was unavailable in that publication was sourced from The Wood Database.
2. I recommend a region-specific field guide. For those of you in the Southeast, you can’t beat Trees of the Southeast. A good, free resource is Dendology at Virginia Tech.

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