Wood can easily be turned transparent to make energy-saving windows

By Leah Crane

Mendowong Photography/Getty Images

Transparent wood just got even better, moving us a step close to windows that are far better insulators than traditional glass ones.

The standard process for making wood transparent typically involves soaking the wood in a vat of sodium chlorite – a chemical compound used in some bleaches and toothpastes – to remove a structural component of the wood called lignin. However, this takes a lot of chemicals, produces liquid waste that is tough to recycle, and can weaken the wood.

Liangbing Hu at the University of Maryland and his colleagues came up with a method that modifies the lignin instead of removing it completely. It is quicker and uses fewer materials than the standard lignin-removal process, and also leaves the wood stronger.

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Their method stems from the recent discovery that lignin can be made transparent by removing only the parts of the lignin molecules that give them their colour. They brushed hydrogen peroxide, which is often used as a disinfectant, over the surface of the wood and then left it under a UV lamp designed to simulate natural sunlight. After soaking the wood in ethanol to remove any remaining gunk, they filled the pores in the wood with clear epoxy, a step that is also part of making lignin-free transparent wood.

The final product is a piece of wood that transmits more than 90 per cent of light and is more than 50 times stronger than transparent wood with the lignin completely removed. “The transparent wood is lighter and stronger than glass – it could be used for load-bearing windows and roofs,” says Hu. “It can be potentially used to make a see-through house.”

Journal reference: Science Advances, DOI: 10.1126/sciadv.abd7342