Throwback Thursday : The Power of the Professional

The following is adapted from Forest Products Laboratory 1910 – 2010 : Celebrating a Century of Accomplishments.

As we saw in the case of the Crimson Criminal, researchers from the Forest Products Laboratory (FPL) have the ability to trace even the tiniest fibers of crime-scene wood to their source to help bring criminals to justice. In some instances however, when evil-doers leave only dust in their wake, conventional analysis is not an option, and an exact identification of the material can be impossible. Researchers instead must instead rely on experience, deduction, and inference to reach a logical conclusion.

A sample of the wood filler (sawdust) used in bombs confiscated in Central America.

The wood filler (sawdust) used in bombs confiscated in Central America was examined to see if the bombs were made outside the region and trace the explosives to their producer. The theory was that wherever the bombs were made, local sawdust would be used.

The fragments were so small that they could not be sectioned. Regis Miller, from the Center for Wood Anatomy Research at FPL, examined the fragments under a light microscope, looking for anything that could be recognized as a species of north temperate origin. He was unable to identify the species of any fragments, but concluded that the wood filler was probably tropical in origin.

Miller was able to make that statement because the fragments did not have spiral thickenings, a feature common to many north temperate species. In addition, almost all the fragments were hardwoods. This is expected of tropical sawdust because most trees in the tropics are hardwoods; in the north temperate regions, softwoods are much more common.


The fragments of the wood were so small, they could not be properly sectioned for analysis.

The only softwood fragment in the dust closely resembled a species of Podocarpus, one of the few softwoods confined to the tropical regions. He also found a fragment from a monocot (perhaps a palm), several fragments that contained a large amount of prismatic crystals in axial parenchyma cells, and fragments with small parenchyma cells or chambered cells.These features are fairly common in tropical species, but are rare in north temperate species.

Even though the exact species of wood remained a mystery, Miller concluded that the sawdust used in the explosive devices was consistent with material of Central American origin, and was confident enough to submit this opinion to law enforcement officials to help apprehend the explosives manufacturer. Miller’s observation and analytical skills are a testament to the power of science professionals, who fill the gaps when conventional analysis fails, and prove that the backbone of all science is the not the research, but the researcher themselves.

Throwback Thursday: Propeller Production at FPL During WWI

Wood propeller research and production was a major focus of activity at the Forest Products Laboratory (FPL) during World War I. During this time, the University of Wisconsin cooperated with and supported the Lab by providing the extra space needed for propeller production.

As shown in the poster below, in addition to the main location of the laboratory, the University provided space in their education buildings, soil building, and agriculture engineering building, for FPL’s airplane parts and woods laboratories, as well as an experimental propeller factory.6900

Laboratory staff worked around the clock to develop and manufacture wood propellers that could withstand the drastic changes in humidity they were likely to encounter. Click on each of the historic photos below to get a closer look on our Flickr page.

FPL research on propeller blades that resist warp, twist, and unbalancing with changes in humidity.

Experimental propellers produced from seven species of wood.

FPL staff involved in propeller research, 1916.

Manufacturing propellers at the FPL. Ten propellers were produced per week by workers on a three-shift-per-day schedule.

Throwback Thursday: Displays from Back in the Day

Today’s digital world enables the creation of stunning visual displays to convey information. Images and words can be combined in a flash to quickly produce striking and effective communications products.

But looking back at these educational displays crafted at the Forest Products Laboratory in the 1950s and 1960s, there’s something to be said for the creativity, time, and use of materials that went into telling the stories of FPL research.

Click each photo to view it larger in Flickr.


Throwback Thursday: Early Large Engineered Wood Structures

There’s a lot of buzz in the world of wood these days about building tall. Designs for high-rise buildings with wood as a main structural component are possible today thanks to engineered wood products like glued-laminated beams and cross-laminated timbers.

A century ago, the construction of large structures was limited by the size of the wood cut from trees and the methods of connecting the members. As Forest Products Laboratory (FPL) researchers amassed knowledge of wood properties, adhesives, and connectors, the use of wood in structures expanded greatly. Here are a few early examples from the 1940s.

Baird Creek Bridge, 1940s

Baird Creek Bridge, 1940s

The Baird Creek Bridge in Washington was an early masterpiece in timber trestle construction. The bridge was 1,130 feet long and 235 feet high. Wood members were held together with a split ring connector at each end connection.

U.S. Navy hanger, 1940s

U.S. Navy hanger, 1940s

The wood structure under construction in the photo above was to be used for storing lighter-than-air airships like dirigibles for the U.S. Navy. The hangar is 1,058 feet long and 174 feet high, with a 234-foot clear span. It required over 3 million feet of fire-retardant lumber.

(Excerpt from John Koning’s book Forest Products Laboratory 1910-2010: Celebrating a Century of Accomplishments.)

Throwback Thursday: Early Fire-Retardant Treatments

In the early days of developing fire-retardant treatments, researchers at the Forest Products Laboratory (FPL) investigated about 130 treatments. Combinations of chemicals were used to obtain the best performance for both fire resistance and other performance properties, such as corrosion, leaching, gluing, finishing, and cost.

Chemicals tested included ammonium sulfate, mono- and di-ammonium phosphates, ammonium chloride, zinc chloride, borax, and boric acid. The phosphates were identified as the most effective. These chemicals were used in the first generation of commercial fire-retardant-treated wood in the United States.

Fire retardant test at FPL, 1940s.

Fire retardant test at FPL, 1940s. (click to enlarge)

The 1940s test pictured above shows an attic section in which the rafters, roof boards, inside of the end wall, and the top ply of the flooring, were impregnated with a moderate degree of fire retardant and exposed to a 5.25-lb magnesium bomb. The treatment completely stopped the spread of fire on exposed surfaces, but the untreated subfloor was ignited by the excessive heat transmitted through the flooring.

(Excerpt from John Koning’s book Forest Products Laboratory 1910-2010: Celebrating a Century of Accomplishments.)