Identifying ash

Q: How can I separate white ash from black ash. I think our supplier is slipping some black ash into our white ash; at least the wood is much browner.

A: It is difficult to separate the ashes, 100 percent of the time, by outward appearance. You really need to use a little magnification, about 10x. But even then, some of the ashes interbreed or may grow under unusual conditions, so it is a tough, maybe impossible, job to be perfect everytime.

There are two groups of ash lumber: white ash lumber and black ash. Actually, white and green ash trees, which both grow in the eastern and central United States and Canada, produce lumber that is so similar that we cannot separate the lumber, even under magnification. Oregon ash is also similar in appearance to white ash, but the geographic source lets us identify this lumber.

There are three clues that we can use to separate black ash from all the others. Black ash is lighter weight than the others. Black ash has very little sapwood (the white colored wood is sapwood) in the tree and even less in the lumber. Black ash grows much more slowly (on the average) than the other ashes, so ring spacing is very close. Under magnification, when looking at the freshly cut (with a very sharp knife or razor) end grain cells in an individual growth ring, there will be small bands of white between many of the cells in the latewood of the white and other ashes, but not very often in the brown ash. For pictures, see Identifying Wood by Bruce Hoadley, Taunton Press.

I have some samples in my wood collection and the growth rate for white ash is about 12 rings per inch; for black ash, 28 rings. The density compared to water, called the specific gravity (SG), is 0.54 for black ash and 0.64 for white ash. The white ash is creamy colored; the black ash is dark brown throughout.


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About the author
Gene Wengert

Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 45 years. He is extension specialist emeritus at the University of Wisconsin-Madison.