How Cellulose Degrades Over Time
The action of photosynthesis in plants such as flax, which is used to make linen fabric, produces cellulose. This is a large, complex molecule that gives the cell walls of plants their strength and structure. It is also a molecule that degrades slowly over long periods of time.
During photosynthesis, plants combine water and carbon dioxide to create glucose molecules. Some of these molecules are joined together to form long chains, releasing a molecule of water with each join as each new glucose molecule is added to the end of the chain.
The diagram to the left shows how glucose is transformed into cellulose during photosynthesis. (A) shows two glucose molecules with the right hand molecule flipped vertically. (B) shows the two molecules joined together through photosynthesis to form the first link in a cellulose chain, releasing a molecule of water in the process. (C) shows a cellulose chain of four molecules; cellulose molecules typically consist of thousands of such glucose links.
These long cellulose molecules have a tendency to line up in parallel which causes some parts of the cellulose structure in flax fibres to have an ordered, almost crystalline form.
In other parts of fibre the cellulose molecules are not aligned, producing a disordered or amorphous structure.
There are two ways in which the structure of cellulose changes with increasing age. First of all, breaks appear in the long molecular chains, reducing the average length of the molecules. Second, the parallel chains become more disordered, making the structure less crystalline and more amorphous. These changes affect some spectroscopic and mechanical properties of flax and so measurements of these properties provide a possible basis for new methods of dating linen.
