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How to Make Window ‘Glass’ from Wood

by Francesca Coleman Carr

Wood has always been the best and most flexible building material, despite the dominance of metal.

Being strong, lightweight (for the most part) and easily available all over the world, I can’t see wood going out of fashion any time soon. However, despite making solid foundations for walls, it’s never been too good at making window panes, until now. Researches have found a way to make wood 90% transparent!

Making wood transparent is bound to open up new uses and possibilities for wood, according to researchers. The possibility of making large window-like panels able to let massive amounts of natural light into buildings, for example, is not out of the realms of possibility, claim engineers and architects alike.

This opens up many possible new uses for wood, researchers say. Engineers and architects could use the new material to make large window-like panels that would let lots of natural light into buildings, for example. This might cut down the need for indoor lighting during the day.

 

Lignin Makes This All Possible

The substance that makes all of this possible is called Lignin, it’s brownish in colour and resides inside the wood. Lingin, in short, bonds with the cellulose and other substances in a planet’s cell walls, part of the reason that makes the wood so strong.

Removing lignin from wood is an essential part of the ‘paper-making’ process. It it a general rule that the more paper you remove, the lighter and whiter the paper will become. This was the rule for some time, however back in 2007, Japanese researchers were able to create transparent paper. Their initial goal was to craft a substance that could be used on modern mobile phones/tablets/LEDs, almost anything that incorporated a touchscreen. They were left inspired by the positive results, as the material allowed more than 90% of light to pass through.

Lars Berglund, a material’s scientist at The Royal Institute of Technology group set out to create a wood emulated the transparency of the Japanese result, though kept its strength and stiffness.

And they succeeded!

The researchers declared their success in crating the innovative transparent wood in the April 11 issue of Biomacromolecules.

 

The Science Behind the Wood

Strangely enough the most difficult part of this process was removing the lignin. This was done by soaking sheets of wood 3mm thick in a bath of acid for 6 hours, and the thicker sheets (including some that were double the thickness) were left to bath for 12 hours. The purpose of these acid baths was to test whether the solution would be able to penetrate the wood, eliminating the lignin binding it together, which it did!

Lingin was making up 30% of the wood’s weight, and after it’s acid bath, it only made up a measly 3%. Fortunately, the acid did not negatively impact the wood’s overall structure, even the cells inside the wood remained intact. Under a microscope, the wood looked similar to that of a bathroom sponge.

Berglund’s next step was to soak the remaining wood in methacrylate (MMA), as its molecules link to form a clear, shatterproof substance. You may have heard it under other more recognisable names, such as Plexiglas and Lucite.

MMA is first heated until its molecules bond together, though remain in their liquid form. This is then poured onto the framework of the wood and soaked in. However, to speed-up this process, the researchers placed every into a vacuum chamber, which in turn, helped force the solution into the wood. They then baked the wood for around 4 hours at 150 degrees, which then bonded the rest of the MMA liquid, forming a clear, solid material.

 

Why Make it in the First Place?

In the near future, businesses look to use less indoor lighting (due to energy consumption and costs) meaning they may invest in the aforementioned lingin process, as forming outer walls out of this strong, durable and clear material is both environmentally friendly and cheap.

 

Refraction is Always a Challenge!

That bending of light that happens during the process of creating this glass results from a process called refraction.

Every transparent material has something called an index of refraction. You’ll find that many materials hold the index number of 1 or 2. The higher the difference in index, the more light will be bent as it moves through one material to the other.

Our wood’s index of refraction, is somewhat of an anomaly, in that it’s almost exactly the same as solid MMA. Berglund claims this is what separates his research team from others, the near-perfect match means that the light that passes through the wood composite isn’t scattered as much. Instead of appearing the typical cloudy white, it’s actually incredibly transparent.

Almost 85% of the light shining onto one side of the hard sheet of the composite will exit out the other side. You may even be able to read through the material, if you’re close enough!

Amit Naskar, a materials scientist at ORNL (Oak Ridge National Laboratory), stated that matching the index of refraction for each material in the new composite “is a very smart approach.”

In the long run, Berglund envisions his transparent wood being used to replace window with big panels, which would allow large amounts of daylight to flood into a building/property. It would also be very eco-friendly, as less artificial lighting (and energy) would be needed in these buildings.

 

Envisions For Future Use

However, Naskar envisions other areas where this potential could be maximised. Due to the material being both clear and strong, he sees it being used in the packaging industry as its twice as strong as Plexiglas and could even replace is, which would see designers use less of it in production. Look at it this way, something made of Plexiglas alone could use the same thickness of the new material, ending up with a product double the strength and using less material.

Naskar goes further, stating that they wouldn’t necessarily need to keep the material transparent. Dyeing it could tempt engineers and other pioneers to use the material to craft car parts, for example.

In short, something now made of Plexiglas alone could use the same thickness of the new material and end up with a product twice as strong. Or, they might use just half as much — which would weigh only half as much — and have a material as strong as the original.

Finally, Naskar notes, designers  wouldn’t have to keep the composite transparent. They could dye it any color. He envisions engineers might then then use the material to make things like vehicle parts.

 

Did you know about any of this? How incredible is lingin! I’d love to hear your thoughts on this topic, feel free to comment below with your thoughts!

 

 

team francesca

Francesca is the Managing Director of Sash Windows London Ltd, a family-owned and professionally managed window company providing a full range of sash window products throughout the UK. Passionate about providing high-quality, friendly, and reliable services. You can read Francesca’s full bio here.

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