Most knitters are familiar with traditional cotton yarn for knitting. It's commonly called kitchen cotton because it is often used for dishcloths, washcloths and other projects that can take a lot of abuse.
This yarn is strong, durable, takes (but doesn't necessarily hold) color well. It can be a little hard on your hands.
What is Mercerized Cotton?
Mercerized cotton is a special kind of cotton yarn that is more lustrous than conventional cotton.
It is also stronger, takes dye a little more readily, makes the yarn more resistant to mildew and reduces lint. It also may not shrink or lose its shape as much as "regular" cotton.
Luster, by the way, is caused by the way light reflects off the surface of things. Eliminating the fuzz or lint from the cotton is part of what makes mercerized cotton so shiny.
Mercerization, the process by which mercerized yarn is made, is named for the British chemist John Mercer, who developed the process and received a patent for his work in 1851.
How is Mercerized Cotton Made?
Mercer found that adding caustic soda (lye) or sulfuric acid to cotton made the fiber swell and straighten. No one was too impressed by that, but in 1890 Horace Lowe developed a process by which caustic soda was added to the yarn under high tension, which added the luster that mercerized cotton is famous for today.
Long, fine cotton threads are usually used for mercerization, such as Egyptian and Pima cotton, because they require less twist than other fibers used in the process.
Mercerized yarn stays shiny through washing and gives a nice, somewhat fancier look to finished items.
Uses for Mercerized Cotton
Mercerized yarn is also sometimes called pearl cotton or pearle cotton, and fine crochet thread used for doilies and other delicate projects is usually mercerized.
For knitters, mercerized cotton can be used for a variety of projects. It is a great choice for kids clothing, summer tops, and shawls, bearing in mind that mercerized cotton shares some of the problems inherent in knitting with other types of cotton yarn (heaviness and tendency to stretch when worn that can't be fixed with blocking).
Choosing lightweight yarns for your projects will be better than using heavier yarns. Some openwork might also be a good option because it lightens up the overall fabric, though pay attention to your swatch. A great idea is to work a swatch in the stitch pattern of your choice, wash it and hang it up for a few days to see how much the yarn sags. Then make your pattern choices accordingly.