Windows from transparent wood could replace glass

Wood is a versatile material: it’s strong and it’s light and it’s flexible. But it isn’t translucent or particularly durable. Glass is. But glass isn’t strong or flexible. But what it you could get the better of both worlds by making wood transparent like glass?

A flight of fancy? It no longer is.

A team of scientists at the University of Maryland, in the United States, has developed a process that can make wood stronger and more durable … and also translucent. And that makes their revamped wood an eminently desirable building material. Unlike glass, it’s a good thermal insulator but like glass it is optically transparent.

“Wood has much lower thermal conductivity,” explained Tian Li, a researcher at the university. “In terms of energy efficiency, it keeps a house at a more consistent temperature.”

The see-through wood can create a uniform and consistent daylight distribution all day long without glare effect. It also offers “high-impact energy absorption that eliminates the safety issues often presented by glass.” In fact, the engineers have demonstrated the resilience of their product by hitting a piece of it with a hammer. The translucent wood withstood the impact while a similarly sized piece of glass immediately shattered.

On the downside, wood panels are not as transparent as glass panes. “[About] 85 percent of light comes through,” Li said, adding that transparent wood functions like frosted glass or acid-etched clear glass. “It’s a little bit hazy, but if you hold the transparent wood right against something, you will be able to see the image quite clearly,” the researcher elucidated.

But how did the scientists create a translucent piece of wood in the first place? They bleached a piece of wood by soaking it in sodium hydroxide (commonly known as lye) to remove lignin, a compound that turns wood strong and gives it its brown color. They then soaked it in a “clear liquid” before soaking the thus-clarified wood again, this time in a glue-like epoxy that makes it very hard and clear.

Once that is done, the porous tubes of cellulose within wood, which serve to suck water up from roots towards leaves and pull sugars down towards roots, into effective light diffusers. “You have a uniform consistent indoor lighting, which is independent of where the sun is,” one of the scientists explains. That means that even light from a glancing angle illuminates the see-through wood.

Why does all this matter? Because “Our transparent wood also has a much lower thermal conductivity compared with glass, making it a better thermally insulating building material with a lower carbon footprint,” they say.

But there’s another downside. “Making transparent wood requires using epoxy, so it’s not very environmentally friendly right now,” one researcher said. The scientists are now “experimenting with other types of clear stiffeners, which will include PVP (polyvinylphenol), which is recyclable.”