Wood Science 101: Wood Species ID and Macrophotography

By Chuck Ray | Posted: 04/13/2013 10:53AM

 

Chuck Ray, PennState, Associate Professor of Wood Operations One question that wood scientists get asked more than any other is..."What type of wood is this?" Sometimes the answer is easy, but often it isn't.

Tree identification is simple by comparison. With a tree, you have leaves, needles, and/or twigs, which are usually a dead give-away of a tree's species. Then, you have identifiers such as whether the leaves are alternating or opposite, the appearance of the bark, and even where the tree is growing. All these factors can also be referenced on a dichotomous (this-or-that) key, which asks you to compare traits until finally, you wind up with the right answer.

Wood is tougher, generally. With wood, you're usually handed a block of wood, typically finished with a stain and/or sealant, or you're asked what kind of wood is this table, or that cabinet, or this old walking stick. So references are limited to color, grain, defects, texture, and sometimes smell...and all of these can be deceiving.

For instance, most people have little trouble identifying an oak table or chair. (See slide show sourced from artisansofthevalley.com.) Oak has a distinctive look, due to the presence of rays, which are darker, fingernail-sized or larger, streaks in the lighter wood. And regardless of the direction of the grain, these rays are apparent and give the wood its unique rustic oak look.

But wood scientists and collectors know that there are hundreds of different oak species, and identifying one from another is next to impossible for most of us. Even wood identification guru Bruce Hoadley admits in his book Identifying Wood that "Separating the many oak species is another matter - the best we can do is assign the wood to either the red oak or the white oak group." Generally, the rays tend to be shorter in the red oaks.

As another example of commonly mistaken identity at an even higher taxonomic level, it's also difficult to tell black cherry from Pacific red alder or "Chinese Cherry" or similar other tropical species that are marketed as cherry. Overseas furniture makers often take advantage of this difficulty to market their furniture as "cherry" or whatever other name is most popular with the local populations.

This difficulty in identification, compounded by different woodworking and finishing techniques, means that even the experienced wood connoisseurs can and will make mistakes. And why truly accurate wood identification requires microscopic examination and a knowledge of the cellular structure of wood. That is what makes the art and science of wood identification fascinating to wood collectors and a nightmare for wood technology students.

Wood species identificationCherry, alder, or other? http://www.wallbedsbywilding.com This was all brought back to me by a series of three videos. A distinguished member of the International Wood Collectors Society, that very same group I visited in a recent column at their Florida convention, has posted these videos demonstrating a technique he has developed for preparing and photographing wood samples under magnification. His name is Jean-Claude Cerre, and his photographs are stunning. The videos are freshly uploaded, and according to YouTube, have only been viewed by a couple of hundred folks. So you, reader, are among the very first in the world to see these wonderful images.

In the first video (at the top of this column), Cerre explains why he has undertaken this task and shared it with the world. During this introduction, various photographs of his work are shown. All are photographs of the transverse, or cross-section view of the wood, for, as Mr. Cerre explains in the video, "the transverse structure of wood is like a fingerprint in humans." The transverse section is the equivalent of looking down at the top surface of a stump of a tree, or at the end of a piece of lumber...you're looking into the open tube-end of the wood cells that were discussed in our last post in this series about water movement in a tree.

Since the samples are all identified in the video by their scientific names, I thought you would like an easy way to reference them to their common names. Here is a list of the samples in the order they are shown, with their common names.

1.Quercus ellipsoidalis x10 Northern Pin Oak 2. Erythrophleum ivorense x10 Missanda
3. Marmaroxylon racemosum x10 Marblewood 4. Caesalpinia libidibia x10 Partridgewood, Coffeewood
5. Cordia trichotoma x10 Peteribi 6. Cercis siliquastrum x10 Judas Tree
7. Quercus dunnii x90 Dunn Oak 8. Quercus ellipsoidalis x10 Northern Pin Oak
9. Quercus ellipsoidalis x90 Northern Pin Oak 10. Bocoa prouacensis x10 Bocoa
11. Calophyllum spp x90 Callophyllum 12. Carya illinoinensis x90 Pecan
13. Chlorophora excelsa x 10 African Teak 14. Fraxinus americana x 10 White Ash
15. Hymenolobium x 10 Hymenolobium 16. Bambusa blumeana x10 Bayog
17. Dalbergia melanoxylon x 10 African Blackwood 18. Couratari spp x 10 Couratari
19. Ceratonia siliqua x 10 Carob Tree 20. Bursera simaruba x 10 Gumbo-limbo, Copperwood
21. Chlorophora excelsa x 10 African Teak 22. Marmaroxylon racemosum x 10 Marblewood
23. Quercus ellipsoidalis x 10 Northern Pin Oak 24.Quercus ellipsoidalis x90 Northern Pin Oak
25. Intsia spp x 10 Intsia 26. Intsia spp x 90 Intsia
27. Jessenia bataua x 10 Pataua, Seje, Milpesos 28. Castanea sativa x 10 Sweet chestnut, Marron
29. Carya illinoiensis x 10 Pecan 30. Carya illinoiensis x 90 Pecan
31. Canarium tonkinense x 10 Chinese White Olive 32. Peltogyne densiflora x 10 Purpleheart
33. Mulettia laurentii x 10 Wenge 34. Mulettia laurentii x 90 Wenge
35. Platymiscium trinitatis x 10 Platymiscium trinitatis 36. Pisonia zapallo x 10 Pisonia zapallo
37. Pisonia zapallo x 90 Pisonia zapallo 38. Dimorphandra hohenkerkii x 10 Dimorphandra hohenkerkii
39. Diplotropis purpurea x 10 Many 40. Eperua falcata x 10 Wallaba
41. Eperua falcata x 90 Wallaba 42. Mullettia laurentii x 10 Wenge
43. Peltogyne densiflora x 10 Purpleheart 44. Pistacia mutica x 10 Mt. Atlas Mastic
45. Pistacia mutica x 90 Mt. Atlas Mastic 46. Rhamnus catharticus x 10 Buckthorn
47. Platymiscium trinitatis x 10 Platymiscium trinitatis 48. Roupala sessilifolia x 10 Roupala sessilifolia
49. Rhamnus catharticus x 10 Buckthorn 50. Pycnanthus angolensis x 10 African nutmeg
51. Sassafras albidum x 10 Sassafras 52. Laburnum anagyroides x 10 Common Laburnum
53. Laburnum anagyroides x 90 Common Laburnum

And here is the video...
Next video (Part 2) is a great hands-on, step-by-step, demonstration of the process by which he prepares the samples. Sample preparation is, like in any artistic endeavor, a key component of the quality of the final product.
And finally, is the video (at the bottom of this column) in which he demonstrates how the samples are photographed under the microscope. You'll especially appreciate how high-tech the camera and software is, these days, for macrophotography.
Thank you, Mr. Cerre, for this excellent lesson on wood sample macrophotography, for sharing your photographs, and especially for making the effort to include a Google Translate computer voice in your video so that the non-Francais speaking world may enjoy and learn.
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About the Author

Chuck Ray, PennState, Associate Professor of Wood Operations

Chuck Ray

Dr. Charles D. “Chuck” Ray is Associate Professor of Wood Operations Research at Pennsylvania State University. His specialty is in the area of operations research, specifically those operational issues that confront the majority of the wood products sector. He previously spent 15 years in research and quality management for two large building products corporations, Temple-Inland Forest Products and Louisiana-Pacific. Ray is the sixth generation of his family to work in the sawmill industry, the Ray Brothers Lumber Company, established in East Texas before the turn of the last century. He can be reached at cdrpsu@gmail.com and followed on Twitter @ChuckDRay. He maintains an Extension website for Penn State at http://extension.psu.edu/woodpro and also writes a blog on all wood issues called Go Wood which can be found at http://gowood.blogspot.com.

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