MITRA Forum Question Details

Both are cellulose fibers which weaken with extreme age due to oxidation, acidity, and the destructive effects of painting materials, UV light and pollutants. Our conservation specialists will no doubt be better able to explain the aging mechanisms.

In the short term, flax fibers (bast fiber from the plant stem) are stronger and much longer than cotton (boll fiber)​. The longest, strongest flax fiber is produced by spacing plants closer together to reduce branching. Flax grown for seed is spaced farther apart to encourage branching; a fiber crop is still harvested, but it's shorter and rougher than top quality "line" fiber. Lower quality linen thread is slubby, and the resulting "sack cloth" sometimes even has bits of tow in it. To obtain the full length fiber, flax is mechanically grubbed roots and all- never mowed or cut.

​Matthew's response above is quite helpful here but we have also sent this question along to one of our textile experts. As for the rigid support question, no, there will be no noticable difference (other than color, texture, etc.) once mounted to a rigid support.

​Here is a response from one of our textile experts: 

As is so often the case in conservation the short answer is: it depends. It's true that if you compare *fibers* that linen is stronger than cotton because of greater fiber length and higher percent of crystalline structure. But the strength of a fabric is never just about fibers. Fabric is made of threads that can be thick or thin, single strands or plied, tightly or loosely twisted. The fabric can be more densely or more loosely woven. The threads and weave can be more consistent or have more irregularities. All of the structural properties of the thread and weave influence the strength and stability of the fabric. So depending on the threads and weave structures, you could have a specific cotton fabric that is stronger than a specific linen fabric. Also, fibers are often bleached or given different chemical processing during spinning or weaving, and these chemical processes can influence strength (for example, mercerized cotton has higher tensile strength than un-mercerized). With paintings, there are other factors to consider including the way the fabric is stretched and the evenness of the tension. 

Laura Mina