What Is Mercerized Cotton?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon
Mercerized cotton is cotton which has been treated with sodium hydroxide which strengthens it and makes it smoother.
Mercerized cotton is cotton which has been treated with sodium hydroxide which strengthens it and makes it smoother.

Mercerized cotton is cotton which has been treated with sodium hydroxide to bring out certain properties first discovered by John Mercer in 1851. In 1890, Horace Lowe added an additional step to the process, and the British cotton industry began to take an interest in this type of cotton, which is available today in a wide range of incarnations from thread to completed garments. When treated properly, mercerized cotton is stronger, smoother, and shinier than regular cotton. In addition, it takes dye more readily so that manufacturers can create rich color saturation in their cottons. The brilliant, lustrous hues of this cotton can be found in fabric stores, yarn shops, and department stores all over the world.

John Mercer discovered that immersing fibers such as cotton and linen in a caustic soda bath would increase their strength and also allow them to take dye more readily. He patented his fiber work, but the cotton industry did not express very much interest in it. It was Horace Lowe who popularized the process, by discovering that keeping the fibers under tension while they were soaked yielded a more lustrous thread. Mercer's name is presumably given to the process to recognize his important initial discovery, which paved the way to Lowe's refinement of the treatment.

Mercerization starts with gathering the cotton and spinning it normally. Because cottons with long fibers take better to mercerization, Pima, Egyptian, and Sea Island cotton are usually chosen for the process. The cotton thread is held under tension and submerged in a highly alkaline bath of sodium hydroxide in a percentage which ranges, but usually hovers around 22%. After treatment, the mercerized cotton is placed into an acidic bath to neutralize it. Once this process is complete, the cotton can be dyed and knitted, woven, or packed as stand-alone spools of thread.

The terms "pearl cotton" and "pearle cotton" are also used to refer to Mercerized cotton, because of the deeply lustrous appearance of the finished cotton thread. In addition to having rich color saturation and a shimmering appearance, this fabric is also much stronger than conventional cotton thread. The process shrinks the cotton fibers, tightening and smoothing the grain of the thread. Because the cotton is preshrunk, mercerized cotton also tends not to shrink as much as regular cotton, so consumers can be more confident about the fit of mercerized garments.

Can You Dye Mercerized Cotton?

Mercerized cotton offers a number of benefits. Not only are mercerized fibers strong, but the mercerization process also ultimately causes the cotton fibers to tighten up. That tightening means your items are unlikely to shrink further once you complete your project. One of the most beneficial things about mercerized cotton is its ability to absorb dye and create vibrant colors.

The process of mercerization causes the surface area of the yarn to expand and tighten. Because mercerized cotton fibers have a larger surface area than other cottons, mercerized cotton will actually take dye much better than fabrics that aren't mercerized.

However, be aware that, because mercerized cotton absorbs dye so well, you're likely to end up with a different shade than if you used non-mercerized cotton. Dyed mercerized cotton generally comes out richer or darker than other materials. That means you have to be careful when choosing your dye to ensure you don't end up with the wrong color.

Can You Use Mercerized Cotton Thread In Microwave?

If you plan to make hot pads, heating bags, or any other items that might go in the microwave, mercerized cotton is an excellent choice. Since it's a natural fiber, it isn't at risk of melting like a poly-fiber might be, although a microwave typically won't get hot enough to melt poly fabrics. In addition, the mercerization process makes the thread stronger.

Adding Other Materials To Your Item

Although you can microwave mercerized cotton, you'll have to be careful about what else you add to your project. Elastics and certain plastics can weaken or even melt in the microwave. Likewise, anything metallic can cause the item to burn or damage the microwave. So, when you're constructing your hot pad or bag, be sure to only use pieces that will stand up to repeated use in the microwave.

How To Wash Mercerized Cotton

One of the most significant benefits of mercerized cotton is that the mercerization process actually pre-shrinks the thread. That means if you knit a sweater or microwaveable bowl cozy, they're unlikely to shrink when you put them in the wash.

In addition, the fabric's ability to accept dye makes it colorfast, so you won't have to worry about your items fading, either.

That said, some mercerized yarns and threads can come out of the wash feeling stiff, which can be frustrating when it comes to clothing such as shirts and sweaters.

So, how do you wash mercerized cotton?

Mercerized cotton actually doesn't require any special care. However, there are a couple of ways to wash your items to help them last longer.

Hand Wash

First, you can hand wash your items. This can be time-consuming, but it will give you more control over the drying process, which can help avoid wrinkling.

To properly hand wash your mercerized cotton clothing, soak your items in cold water for two hours, then roll them in a towel to get rid of any excess water. Once they're barely damp, you can iron them to smooth out any remaining wrinkles.

Machine Wash

Your other option for washing mercerized cotton is to wash it in a washing machine as you would anything else. Unless the label states otherwise, you should use warm water for the washing cycle. Dry them until there's only a small amount of moisture left, then iron them.

When washing your clothes, a good rule of thumb is to give them a shake when they come out of the washer and dryer to kick-start the de-wrinkling process. Mercerized cotton is fairly wrinkle-resistant, but some clothing items tend to come out wrinkled in certain dryers, such as high-efficiency machines.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a HomeQuestionsAnswered researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a HomeQuestionsAnswered researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments

anon1005511

I notice that cotton garments that are years old and have been machine washed hundreds of times, suddenly shrink to several sizes to small. I was once told it was due to the mercerizing having washed out. That doesn't seem to make sense since the mercerizing chemicals are neutralized and washed out immediately. So what does cause old cotton to suddenly shrink a lot?

anon950640

How can we improve strength via mercerization?

anon342418

I want to buy some woven fabric made in Guatemala that is mercerized. I plan to make a baby carrier with it and do not want my baby next to this chemical all day. Can it be washed out?

anon333468

What are the end uses for mercerization?

anon330972

Some sodium hydroxide could have traces of heavy metals like mercury and nickel. Would these traces of metals end up on the cotton? Can they be removed in the acid wash?

anon84358

The dimensional stability of cotton is improved with mercerization because it the process shrinks the fibers. This is a pre-shrinking that means there is not much dimensional instability left in the fibers. Untreated cotton shrinks. Mercerized cotton shrinks very little, if at all.

The shrinking effect of mercerization also affects the strength because the fibers are more tightly bound since they shrinking and this makes the resulting thread thread much stronger.

This is very like wetting a knot in a rope and not being able to undo the knot because it is so tightly locked by the shrinking that the knot is permanent without destroying the fiber.

anon27558

1-How can we improve dimensional stability via mercerization?

2-How can we improve strength via mercerization?

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    • Mercerized cotton is cotton which has been treated with sodium hydroxide which strengthens it and makes it smoother.
      By: Tamara Kulikova
      Mercerized cotton is cotton which has been treated with sodium hydroxide which strengthens it and makes it smoother.