Wood is an ancient material that humans have been using for millions of years for activities such as building houses and boats or as fuel to fuel fires. It is a renewable resource, and it is also a means through which to absorb the excess carbon dioxide present in the Earth’s atmosphere. Currently, the annual production volume of the main component of wood, cellulose, is 20 times higher than that of steel.
But if there is one thing that we would not use wood for, it would be to build windows. Instead we use plastic and glass, which are transparent and, when hardened, provide structural strength. But buildings lose a lot of heat through glass, and even though the light they let through can temper interiors a bit, it’s not a good insulator. Hence the need to put double glazing. Wood, for its part, has great insulating capacities, but it is not transparent … Normally.
In recent years, materials engineers have been working on creating transparent wood. This material (a wood through which it can be seen, and which at the same time retains its great mechanical properties) could be a good alternative to glass; alternative, in addition, that comes from a sustainable and renewable material. Previous attempts to do this involved enormous energy costs, and also required the use of highly toxic chemicals. However, a new study has recently been published showing how to make transparent wood without using large amounts of energy.
See through wood
The lack of transparency of wood is due to the joint action of its two main components, cellulose and lignin. Lignin absorbs light, and the presence of chromophores (components that are activated by light) makes this material appear brown. Wood fibers, which are mostly made of cellulose, are hollow tube-like structures. And the air inside these tubes scatters the light, limiting their transparency.
Previous research aimed at creating transparent wood attempted, among other things, to completely remove the lignin from the framework and replace it with a resinous material. But to remove the lignin it was necessary to use many chemicals that are very harmful to the environment, and it also involved a considerable reduction in the mechanical properties of the material, which became weaker.
But the new study, carried out by researchers at the University of Maryland, shows how transparent wood can be created using a simple chemical, hydrogen peroxide, which is commonly used to color hair. It is a product capable of modifying the chromophores, of changing their structure in such a way that they stop absorbing light and give the wood its brown color.
This chemical can be spread on wood and then activated by projecting light. In this way, a shiny white material can be obtained, which we could call blonde wood. The chemical reaction that occurs when joining wood and hydrogen peroxide is well known, as it is a basic procedure to discolor the wood pulp that is used to make paper (and that is one of the reasons why said paper has a banque and shiny appearance).
The other reason why paper is white is because the pores or holes that make up its structure scatter light in a similar way to how hollow cellulose fibers do in wood. If these fibers are filled with resin, dispersion is reduced, allowing light to pass through the wood and making it transparent while maintaining its mechanical properties.
We are talking about fascinating research that is based on the well-known chemical reaction that occurs when hydrogen peroxide and lignin come together. This technique could equally be applied to large material structures, which could lay the groundwork for the production of transparent building materials that have the real potential to replace glass.
Since the chemical is applied to the wood, this offers great possibilities for creating decorative effects. Thus, the use of panels of this new material in interiors could become popular, where they would continue to provide their additional insulating capacity.
Further research is needed to optimize the chemical reaction and achieve industrial automation of the process. However, a day will come when we will be able to sit inside a house or work in a building whose windows are completely made of wood.