Wood Identification

The first step to properly utilize wood is to correctly identify the species.  Wood species have unique anatomical characteristics that allow a trained eye to identify the species.  These unique anatomical characteristics are also important in determining many of the properties of the species, such as strength, dimensional stability, acoustical, conductivity, ease of pulping for paper and other applications, and energy yield.    Some anatomical properties can be modified by growth rate. 

For example, we all know that faster grown pine trees have wider growth rings but did you know that they also have shorter fiber lengths and higher microfibril angles (MFA) on the S-2 wall.  The MFA is the angle of the cellulose chains on the thickest component of the cell wall and a high angle generally leads to less desirable wood properties.  Be careful when relying upon color or odor to make species determinations.  They can be helpful but also tricky.  For example, I have seen hybrid walnut that did not have the traditional chocolate brown color.  Also, aromatic species will lose their scent over time. 

One final warning, if you see an old “pine” board with tight growth rings, don’t always assume that it is old growth southern yellow pine.  If you see little white dots visible on the latewood (the darker bands) then you are seeing the resin canals, and it is a pine.  If not, it is likely cypress. 

I have served as an expert witness on several cases in which species identification was critical.   The most recent involved a family purchasing very expensive oak flooring and the company represented the flooring as oak.  I was asked to identify the wood species and issue a report of my findings.  It was not oak.  It was a much cheaper wood that was stained with an oak finish.  If you need wood identified for a legal matter, hobby, or whatever, please email me at tfshupe@gmail.com.

In Service Product Failure

One of the most common problems that I have addressed over the years is in service product failure.  The problems range from buckling/cracking of wood flooring to failure of utility poles, chairs, decks, fences, bleachers, roofs, deer stands, ladders, etc.   The first question we must determine is a big one.  Is this a manufacturing problem or improper use/application problem.  I have seen instances when it is clearly one or the other and in some cases both.   As a consumer/user we can’t do much for products that are improperly designed and/or manufactured.  However, we can educate ourselves to try to buy the right product for the job.

The second question we must determine is also a biggie.  Was the product inspected and/or maintained over time?  If so, who did it?, What did they do?  What were their credentials?  Was a standard operating procedure being used to determine the nature and frequency of the inspection?  What documentation do we have? 

One example of improper design was a bar stool that was very tall with three small legs that were connected with glue.  An insufficient amount of glue was applied creating what is known as a starved glue joint.  It was inventible that the chair would eventually fail and it did. 

Photo of glue joint – courtesy USDA Forest Service

The interaction of wood and glue is important to develop a good bone and avoid product failure.

Poles that fail in service are carefully examined to determine if it was properly manufactured, type of preservative used, wood species, name of treater, year of last inspection, and pole class.  Then records are evaluated to determine the frequency and scope of inspections.  (Courtesy Dr. H.M. Barnes, Mississippi State University)

Why Did My Deer Stand Deteriorate So Quickly?

Deer stands should be made with treated lumber and plywood or OSB.

I love to deer hunt and have many friends that do also.  In the US South we are in the harshest decay zone due to our high temperatures and humidity.   Therefore, any wood in contact with the ground must be naturally decay-resistant or preservative-treated for ground contact.  Second, wood composites such as particleboard are a bad idea.  The panels will swell and fail very quickly.  A better option is treated OSB or plywood.  Make sure your ladder to get to your stand is in good condition.  There are far too many preventable human deaths each year in deer stands.  Be safe!

Why Are My Nails So Rusty In Treated Wood?

Rusted fasteners have a thinner actual shaft diameter than a non-rusted fastener and are weaker as a result.

Damp wood can cause metals to corrode.  This is partly because wood is slightly acidic.  When a metal fastener is embedded in wet wood, conditions are created that can accelerate the corrosion of the metal. The corrosion products often result in slow deterioration of the wood surrounding the metal. Corrosion of the fastener combined with deterioration of the adjacent wood causes loss of strength of the joint and weakening of the structural integrity of the assembly. The exposed end of a steel fastener in damp wood quickly shows evidence of hydroxyl ion (OH-) formation. The exposed head of a metal fastener can become the cathode and the shank is the anode of a galvanic corrosion cell.

Dissimilar metals in contact with one another in a corrosive environment form a galvanic cell that results in accelerated corrosion of the less corrosion-resistant metal and very little attack of the more resistant metal. Thus, with dissimilar metals in electrical contact, the more noble metal becomes the cathode and the less noble one becomes the anode. Also, if the anode is iron, then ferrous ions can initiate degradation of the adjacent wood.

Corrosion of certain metals could be a problem in waterborne salt-treated wood in contact with soil when the moisture level of the wood is high.  This led to a resurgence in galvanizing and other coatings for fasteners and a reformulation of the copper in many copper-based wood preservatives.

REFERENCE: Baker, A. J., ‘‘Corrosion of Metal In Wood Products,” Durability of Building Materials and Components. ASTM STP 691. P. J. Sereda and G. G. Litvan, Eds., American Society for Testing and Materials, 1980, pp. 981-993. ABSTRACT: A description is given of the source of metal corrosion products that caus