Do you want mercerized or unmercerized cotton? What’s a “pearl” or “pearle” cotton? What is “mercerization” and how does it affect the cotton? Simply, mercerization alters the chemical structure of a cellulose fiber, and “pearl” or “pearle” cottons have been mercerized.
“Mercerization” was named after its developer, John Mercer of Great Harwood, Lancashire, England, in the mid-19th century. (Wikipedia says 1844, but in Textiles by Kandolph, Lanford, Hollen & Sadler, the authors date the invention to 1853. I would posit that the dates differ depending on what one views as the date of the development: the initial experimentation and invention? its improvement? its first commercial use? the acquisition of a patent?) Mercer was a dye and fabric “chymist” as well as a calico printer. After inventing the process, he was admitted to the Royal Society, the Philosophical Society and the Chemical Society. (Pretty impressive for someone with a complete lack of formal schooling!)
What is it?
By using an alkali mercerization alters the chemical structure of a cellulose fiber. It can be done on yarn (“yarn mercerization”) or fabric (“fabric mercerization”). Mercer used sodium hydroxide (aka caustic soda or lye) to treat cellulose fibers (e.g. cotton, linen or hemp). The process shrank the cotton which became stronger, more lustrous and more absorbent. The picture to the left of the cross-section of a cotton fiber shows the post-mercerization increase in absorption. (Pic source) Not surprisingly, the process made it easier for Mercer to dye or print the resultant fabric. The process also made cellulose fibers more durable.
Despite all the benefits, mercerization wasn’t popular as 19th century mill owners feared people would use less fabric. In the 1890s, however, H.A. Lowe discovered that if you held the fabric under tension, it not only did not shrink but its luster increased and the fabric felt silkier. It’s been popular ever since. 🙂
So, in sum, mercerizing cotton:
- increases its fiber’s strength (up to 30%) and thus durability;
- causes it to swell, thus increasing its absorbency (approx. 11%);
- allows dyes to enter the fiber more readily and have better colorfastness;
- increases the fiber’s luster because the fibers become rounder and reflect more light; and
- raises its resistance to mildew.
Today mercerizing process, in addition to being used on cotton and linen, is sometimes used on rayon. (For more reading, take a peek at Tom Beaudet’s article, “What is Mercerized Cotton?“)
Which to Use?
It depends on the fiber artist and the project. If dye fastness, durability and luster are important to you, you may want to go with mercerized cotton. Mercerized cotton holds ribbing better. That said, if you use a naturally colored unmercerized cotton, the color won’t fade.
Many weavers, knitters and crocheters prefer to use unmercerized cotton for projects such as table linens and towels.
When do you use mercerized as opposed to unmercerized cotton – or vice versa?