Working with Unknown or Obscure Woods

By Eric Meier

You’ve got a piece of wood, maybe it was inherited or passed along from someone, and you’re not sure what it is. Your best attempts at identification have turned up fruitless. Or perhaps you’ve cut down a standing tree (or recovered a storm-damaged tree) and you know exactly what you’ve got—but it’s a very obscure species with no available information (it would be pretty awesome if you could send me a piece). In these instances, it helps to keep a few guidelines in mind to help get the best out of the wood.

Stereotypes can be good…

…When it comes to wood, that is. Basically, there are certain characteristics that are observable in wood, which can help give hints as to how a wood will probably behave when being worked. While not infallible, they are much better than flying blind. 

The following could be thought of as a list of “wood stereotypes” in a sense, and they should help give a better idea of what to expect when working with an unknown or obscure piece of wood.

1. Get a sense of the wood’s weight

This is number one for a reason. Density is probably the single best indicator of how a wood will behave in terms of workability and strength. The USDA’s Forest Products Laboratory uses it to predict hardness, and Australia’s research branch CSIRO has developed tiers of expected minimum strength values based on a wood’s density.

Minimum values (at 12% MC)

Modulus of Rupture: 6,530 lbf/in2 (45.0 MPa)

Elastic Modulus: 1,146,000 lbf/in2 (79.00 GPa)

Crushing Strength: 4,350 lbf/in2 (30.0 MPa)

Minimum values (at 12% MC)

Modulus of Rupture: 7,980 lbf/in2 (55.0 MPa)

Elastic Modulus: 1,320,000 lbf/in2 (91.00 GPa)

Crushing Strength: 5,220 lbf/in2 (36.0 MPa)

Minimum values (at 12% MC)

Modulus of Rupture: 9,430 lbf/in2 (65.0 MPa)

Elastic Modulus: 1,523,000 lbf/in2 (105.00 GPa)

Crushing Strength: 5,950 lbf/in2 (41.0 MPa)

Minimum values (at 12% MC)

Modulus of Rupture: 11,310 lbf/in2 (78.0 MPa)

Elastic Modulus: 1,813,000 lbf/in2 (125.00 GPa)

Crushing Strength: 6,820 lbf/in2 (47.0 MPa)

Minimum values (at 12% MC)

Modulus of Rupture: 13,630 lbf/in2 (94.0 MPa)

Elastic Modulus: 2,031,000 lbf/in2 (140.00 GPa)

Crushing Strength: 7,830 lbf/in2 (54.0 MPa)

Minimum values (at 12% MC)

Modulus of Rupture: 15,950 lbf/in2 (110.0 MPa)

Elastic Modulus: 2,321,000 lbf/in2 (160.00 GPa)

Crushing Strength: 8,850 lbf/in2 (61.0 MPa)

Minimum values (at 12% MC)

Modulus of Rupture: 18,850 lbf/in2 (130.0 MPa)

Elastic Modulus: 2,683,000 lbf/in2 (185.00 GPa)

Crushing Strength: 10,150 lbf/in2 (70.0 MPa)

Minimum values (at 12% MC)

Modulus of Rupture: 21,760 lbf/in2 (150.0 MPa)

Elastic Modulus: 3,118,000 lbf/in2 (215.00 GPa)

Crushing Strength: 11,600 lbf/in2 (80.0 MPa)

DON’T BE THAT GUY. Everyone thinks wood is heavier than it actually is. I can’t tell you how many times someone has come to me with a wood question and prefaced it with “this wood table is extremely heavy” or some other statement. 

Compare it to other known woods. Heavier than oak? Lighter than pine? 

Ensure you have properly dried the wood before estimating weight.

2. Check the wood’s color

Taking a step down, perhaps because you can’t accurately weigh the wood. 

Notable exceptions are redwood, etc.

Color generally predicts weight, strength, but also durability. 

Why? Because color comes from heartwood extractives. Extractives are also responsible for imbuing the wood with good rot resistance, better strength and hardness, as well as accompanying odors. Heartwood extractives in most woods is a complicated cocktail of various substances, some understood and researched more than others. But the bottom line is, in general, color is the quickest and easiest way to visually stereotype a wood to get a sense for the amount of extractives. Is it inerrant? No. But it’s far better than a blind guess.

3. Check for wood odor

Generally, scented wood means it is more durable. Heartwood extractives. General indicators, not something to risk your next exterior project on.

Not green odor, but dried wood odor, especially lingering odor.

4. Look at the wood’s grain patterns

ring porous woods are temperate zone. Diffuse porous may indicate tropical origin without distinct growing seasons.

Interlocked grain will be harder to work than straight grain, pretty much across the board (pardon the pun).

Wild and irregular grain is harder to work than plain grain, again, this is true in nearly all instances and species.

Just use common sense with how a jointer or planer works with regard to grain direction. Can you plane endgrain? Not really. The closer to endgrain the you get, the work time you will have.

DENSITY ACTS AS A MULTIPLIER. The wood gets bonus points for difficulty if it has both irregular grain and is also heavy.

Other considerations: burls, roots, monocots. Old growth. Flowering trees vs confiers. (Instead of hardwoods vs softwoods.)

5. Consider the wood’s form

Is it planed and surfaced 4/4 lumber? (It was probably meant for furniture.)  A wax-sealed square blank? (It was probably meant as a turning blank.) Reclaimed wood? A shrub? A massive three foot wide slab? These things have implications, and the more information (and processing) that’s been done to the wood, the more information can be gathered.

A good rule of thumb for unknown wood is to use the wood for what it appears that it was processed for. This may seem painfully obvious, but it’s worth considering that there are certain stereotypical (or, more accurately, prototypical) characteristics for different spheres of woodworking.

Furniture: mid to medium-high density, but not too dense to make it overly difficult to machine.

Construction: Long, straight, lightweight boards with good strength to weight ratio. 

Turning: smaller, heavier, squared pieces with tighter grain and attractive appearance.

Carving: short but stout lightweight pieces that can hold detail well.

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