What is Mercerized Cotton Yarn?

Katriena Knights

Mercerized cotton yarn is a type of cotton yarn that has been produced in a certain way that makes it stronger, more lustrous and less likely to shrink. It also makes the cotton mildew- and lint-resistant and helps it accept dye more readily, allowing for stronger, more brilliant colors. The mercerizing process was developed by John Mercer, a British chemist who patented the process in 1851, but the process was popularized by Horace Lowe in 1890 when he altered the process slightly in order to confer a high luster to the resulting fibers. This type of processed cotton yarn also is referred to as pearl yarn or pearle yarn.

Cotton field ready to be harvested.
Cotton field ready to be harvested.

Producing mercerized cotton yarn involves exposing the cotton fibers to a caustic solution such as lye or sulfuric acid. This causes the fibers to swell, straighten and become rounder, as well as making them absorb liquids, including dye, more readily. In order to increase the luster of the fibers, the most desirable quality in mercerized cotton yarn, the caustic solution must be applied to the cotton while the cotton fibers are held under tension. Tension is held for about 10 minutes while a 21-23 percent sodium hydroxide solution is applied at room temperature. This process not only causes the cotton fibers to swell and straighten, it also makes the fiber surface much smoother, causing the luster for which mercerized cotton yarn is known.

Cotton bolls on a branch.
Cotton bolls on a branch.

Certain types of cotton fibers work better to make mercerized cotton yarn than others because of the way the sodium hydroxide is absorbed and the way the cotton fibers respond to it. In general, mercerized cotton yarn is made from cotton that produces longer fibers, such as Egyptian and Pima cotton, because they do not need to be twisted as much as cotton with shorter fiber lengths. The reduced twist in these fibers also makes them more absorbent.

For knitters, crocheters and other crafters, mercerized cotton yarn comes in a wide variety of sizes and colors. Yarn gauges and yarn weights from very fine, lace-weight yarn to heavier worsted weight can be found easily in any craft store, making mercerized cotton yarn a convenient choice for any project. Cotton yarn in general, though, has a rougher texture and a less delicate drape than other yarns, especially fine wool yarn, alpaca yarn and various handspun and novelty types of yarn. When choosing a type of yarn, it is important to consider gauge, weight and drape.

Mercerized cotton is treated to make it stronger and more lustrous.
Mercerized cotton is treated to make it stronger and more lustrous.

You might also Like

Readers Also Love

Discussion Comments


I had no idea the process for making mercerized cotton yarn was so involved. For some reason I always thought it was just a different kind of cotton plant. You know, like Egyptian cotton or something like that?

It sounds like mercerizing cotton was definitely a product of the industrial revolution! After all, I'd imagine it would probably be very difficult to make mercerized cotton yarn in a non-factory setting.


@strawCake - I'm a knitter also, and I think you're right -- mercerized cotton yarn definitely has it's place in any knitters yarn stash. However, there are some projects I prefer to use just plain cotton for.

As the article said, mercerized cotton definitely has a certain shininess to it. There are certain projects that I wouldn't want to make "shiny," you know? For instance, I really like to make washcloths for my kitchen. They hold up well and they're a nice quick project that's easy to transport.

However, I don't like to use mercerized cotton for this purpose. Who needs shiny washcloths? Nope, I'll take a nice 100% regular cotton aran yarn for these types of projects any day!


I'm a knitter, and I really like to use mercerized cotton yarn for sweaters. I mainly use worsted yarn for sweaters, and luckily plenty of brands put out worsted weight mercerized cotton in tons of colors.

Mercerized cotton yarn is great for sweaters and other garments because it doesn't shrink as much as regular cotton. For a knitter, there's nothing worse than knitting a sweater to your exact measurements, and then accidentally shrinking it in the wash. Using yarn that doesn't shrink too much really helps!

Also, I'm allergic to wool, so my other options for nice sweater yarn are kind of limited.

Post your comments
Forgot password?