There’s a Superhero Beneath Your Feet

Imagine a trail dipping below a steep valley edge surrounded by lush, verdant greens. A brook chatters below and in its soft watery tones invites hikers to a moment of relaxation and communion. The breeze is soft and sweet as the leaf canopy dances in unison overhead. It is idyllic and accessible because of the wooden boardwalk solidly supporting each who visit this natural wonder.

This boardwalk and others like it can be found in many natural areas. But it is made possible by pressure-treated wood, a building material that when processed with the correct preservatives, often outlasts and outperforms durability estimates and usefulness before it can biologically deteriorate.

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Southern Exposure: Long-Term Field Testing of Wood Protectants

When researchers are looking to evaluate the performance of wood protectants, the harsher the environment the better. Which is why Forest Products Laboratory (FPL) researchers put specimens to the test in the Harrison Experimental Forest (HEF) in Saucier, Mississippi, and have been doing so for 80 years.

Generations of FPL researchers have used the HEF field site for sub-tropical field testing. Here Oscar Blew is rating posts at the HEF (1950’s).

Located about 35 miles north of the Gulf of Mexico, this sub-tropical field site receives about 60 inches of rainfall a year and has a mean temperature of 68 degrees Fahrenheit. The wood decay hazard in this area is rated “severe” according to the American Wood Protection Association Use Class Rating System and there is significant subterranean termite activity. When in ground contact, untreated wood rarely lasts 12 months in the HEF, to which researchers respond “challenge accepted.” Continue reading

Meet the Researchers: FPL Scientists Featured in Crossties Magazine

The Railway Tie Association publishes a magazine, Crossties, for producers and users of treated wood crossties and related products. The May/June 2017 issue introduces a new regular feature called “Meet the Researchers,” and it kicks off by showcasing researchers from the Forest Products Laboratory (FPL).

This makes perfect sense, as one of the original goals for early FPL scientists was developing preservatives for railroad ties. More durable rail ties lengthened the service life of ties in use, and helped ease the demand for lumber, as trees were being cut at alarming rates across many northern and western forests.

Over time, lumber treatment and preservation research focused on environmental concerns as well as durability. Today, FPL researchers in the Durability and Wood Protection group continue to work on improving the treatment of wood.

You can read the full issue of Crossties here. See page 13 for the Meet the Researchers feature.

Time in a Bottle: Finding New Life for an Old (Yet Reliable) Test Method

The simple soil bottle presents an extremely useful tool for predicting performance of preservative treated, modified or naturally durable woods. The methodology was developed in the 1940s exclusively for evaluating wood preservatives against wood decay fungi. It has been adapted over several decades to include naturally durable woods, wood plastic composites, and engineered wood products, and we use it constantly here at the Forest Products Laboratory (FPL).

The basic premise of the soil bottle is a material is presented to an actively growing fungus in an otherwise sterile environment. The resistance of the material to fungal degradation is determined by comparison to reference materials (non-durable species or treated reference material). The soil bottle also presents an excellent tool for studying basic fungal biology whereby cellular changes in wood during the decomposition process can be analyzed.  The soil presents a refuge for the decay fungus as well as a source for moisture and transported ions relevant to the decay process.

Past, present and future research at FPL is looking at ways of modifying the standard soil bottle setup to be even more useful for the evaluation of wood and wood protectants. Here are just a few examples of where FPL researchers are pushing the boundaries of the standard soil bottle: Continue reading

Patience is a Virtue: Impressive Decades-Long Research Results

It takes patience to be a scientist. Research can be time consuming, especially when you’re working in the Forest Products Laboratory’s (FPL) Durability and Wood Protection research work unit. Part of the unit’s mission is to treat wood with preservatives and track how long the treated wood can fend off decay. Success can mean decades-long studies.

FPL's Valley View field test site.

FPL’s Valley View field test site.

Recently, several members of the unit made the trek to FPL’s Valley View test site, an unassuming field west of Madison, Wisconsin, where wood in various forms is left to endure the elements, often for years. Their mission: to inspect treated wood stakes that have been buried in the ground for 40 years.

Ground-level view of intact 2 x 4 field stake showing no visible deterioration after more than 40 years of soil contact.

Ground-level view of intact 2 x 4 field stake showing no visible deterioration after more than 40 years of soil contact.

The stakes, both solid wood and plywood, are made of southern pine or western wood species, such as Engelmann spruce and Douglas fir. They were treated with either chromated copper arsenate (CCA) or ammoniacal copper arsenate (ACA).

The results are astounding. There were stakes, both solid wood and plywood, that achieved a rating of 10 (sound) after 40 years of soil contact.  For comparison, untreated southern pine stakes in contact with soil typically last one-and-a-half to two years before failure (rating of zero) due to decay fungi.

Field tests are critical for establishing the durability of treated wood products that are used for construction of decks, bridges, and utility poles. The test site at Valley View has been maintained by FPL since the early 1950’s. Matched sets of many of the studies at Valley View site are also installed in the Harrison Experimental Forest in southern Mississippi, which represents a more severe decay environment due to increased average temperature and rainfall.

Examples of sound (rating of 10) 2 x 4 (top) and plywood field stakes after 40 years of soil contact in southern Wisconsin.

Examples of sound (rating of 10) 2 x 4 (top) and plywood field stakes after 40 years of soil contact in southern Wisconsin.

Blog contributed by Grant Kirker, Amy Bishell, and Stan Lebow.