Reaching for the Cotton …

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.

John MercerBackground.

“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 mercerizationabsorbingabsorbent.  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?

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21 Responses to Reaching for the Cotton …

  1. Crooked Tracks says:

    Very interesting post. I would like to make some dishcloths and now I will look for the right kind of yarn.


  2. Probably because mercerization was invented 150 years ago, we don’t think “Oh, I wonder if it was named after a Mr. or Ms. Mercer?” 🙂


  3. So interesting, I never knew this thanks 🙂


  4. ruthrawls says:

    It’s the Bateson family, and they are in the fiber business, involving cotton, linen, fabric draping, etc. I’ll let you know it I find Mr. Mercer in conjunction with this family!


  5. Maybe the Mercer name will crop up somewhere in your research. 🙂

    Liked by 1 person

  6. I haven’t knit any of those lately, but I used Fiber Trend’s “Bathing Beauties” pattern. I knit up many soap sack and washcloth sets as gifts. I plan on knitting some more for us … I thought would be great for the guest bathroom. 🙂


  7. Yes, Kolibri was a wonderful yarn! I use non-mercerized cotton for weaving dishcloths and washcloths but mercerized cotton when knitting them.


  8. An excellent question, for which I haven’t a response. Your comment is a good reminder for me to think long term – that is, beyond the life of the project.

    Liked by 1 person

  9. Rebecca says:

    I don’t often use cotton either but rather coincidently am knitting some unmercerized stuff I got from a goodwill shop at the mo. Anything that prolongs the life of cotton which has already taken so many resources to make is a good idea but I guess mercerizing also adds to the resource insensity of the product. I wonder if it affects the long term biodegradibility of the cotton.


  10. I like non-mercerized cotton for dishcloths and washcloths. For clothing, I prefer mercerized cotton. Unmercerized cotton makes for a heavy garment. I have a vest/top knit in Dale of Norway Kolibri (sadly discontinued) that has worn like iron and is still going strong.


  11. You’re welcome! You can take the professor out of the classroom … 🙂

    Liked by 1 person

  12. I’ve used mercerized cottons for knitting small projects and frequently use in weaving.


  13. I think anytime we start digging into what might have started as a simple hobby, life gets more complicated! A year ago Thor gave me a Panasonic bread machine for my birthday. I loved it and used it constantly. Now I have multiple starters in the ‘fridge and regularly make an array of preferments (bigas and poolishes, etc.) and am elbow deep into making sour artisan loaves. I have a stack of phenomenal books and magazines on making bread with sour leavening … My friends have started telling me I should open a bakery. (Perhaps they’re just tired of getting loaves of rustic breads from me!)

    Liked by 2 people

  14. I have made and gifted (kept some for myself too!) matching lace patterned washcloths and matching fitted bags for bars of soap out of lustrous mercerized DK weight cotton. They STILL look great and have never mildewed.


  15. I rarely knit with cotton (unless making a lining for a wool hat for Thor), but I have used mercerized cotton a few times to make lacy washcloths and covers for bars of soap. They have held up very well over many years.

    Liked by 1 person

  16. Bekka Poo says:

    Very interesting..thanks for the lesson!


  17. Glenda says:

    I use mercerized cotton when I’m using the thread and have to break out my metal hooks.


  18. Thymewarp says:

    Thanks for a clear description of the process. Its got me thinking about my plant dyeing project quite differently, Alkalinity and acidity just got alot more complex.

    Liked by 1 person

  19. I saw this kind of cotton once and after researching as you explained here realized i shod have bought it for washcloths to use with my home made soap. Great article! Thanks!

    Liked by 1 person

  20. Susan says:

    I didn’t realize linen could be mercerized and wonder if I have ever seen some or maybe have and didn’t know it! I do not care for Pearle cotton and I am not even sure why 🙂 I know, that sounds ridiculous but it does not call my name! Beaudet’s article was interesting, thank you.


  21. ruthrawls says:

    Whoa! I’m researching a family from Lancashire. Not the Mercer family, but still. Lancashire.


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