Mercerization

Mercerization by Renate Giesbrecht
MERCERIZATION Mercerization is a finish applied to cotton yarn or fabric that was discovered by John Mercer in 1851. He found that by immersing fibers like cotton and linen in a caustic soda bath, usually sodium hydroxide or lye, their strength was increased and they were able to take dyes more easily. Because his discovery caused a 20-25% shrinkage loss in cotton cloth and increased the durability of the cloth, the mill men feared that less fabric would be used. In spite of the fact that the industry was not very interested at that time, Mercer did patent his work. The process became popular in the late 1800’s when Horace Lowe discovered that if the fibers were kept under tension while they soaked they did not shrink as much and they became very lustrous and “silk-like”. He found that after sitting in this highly alkaline bath the fibers could be neutralized in an acidic bath. So Mercer discovered the process, Lowe refined and popularized it. Mercerization is used on fibers for many different reasons. It makes threads stronger, smoother, more absorbent, gives luster and increases the ability to take dyes. The process shrinks the fibers and smooths the grain of the thread. Because of this preshrinking, mercerized cotton tends to shrink far less than regular cotton. Greater absorbency results from mercerization because the caustic soda causes the molecular structure to open up so that more water can be absorbed. The moisture regain is about 11 %. This also means that dyes can enter the fiber more readily and when they can be fixed inside the fiber they are more colourfast. Another important gain is increased strength. Mercerization causes a permanent swelling of the fiber which increases strength but also lustre. For this reason these threads are often sought after by weavers to be used for warp. Pearl cotton refers to mercerized cotton and comes in 3/2, 5/2, and 10/2 sizes rather than the 4/8, 2/8 and 2/16 sizes of unmercerized cotton used by the weaving community. by Renate Giesbrecht Source: Textiles by Hollen.Saddler, Langford, Kadolph