Mercerized cotton thread uses a specific process to make the cotton thread stronger, shinier, and easier to dye. This process is used on most cotton thread used in America today. But do you know how it's made? Here's the basic process.
The mercerization occurs after spinning but before dyeing. So the first step is to mill the cotton fibers into a consistent thread. Because the process works better with lower-twist threads, long-staple cotton—which requires less twist to hold together—is ideal.
The thread is wound into big "hanks" similar to the skeins of yarn you'll find at a yarn store. In preparation for the mercerization treatment, these hanks are placed onto two big mechanical "arms" or rollers that hold each hank in place and stretch it tight.
This helps ensure that all sections of the thread can access the treatment solution equally. It's also important to keep the threads pulled tight during the treatment process in order for maximum shininess to develop.
3. Chemical treatment bath
The mechanical arms holding the hanks of thread are then placed into a bath to apply the chemical treatment to the strands. The treatment of choice is a solution similar to the lye used for soapmaking. It's extremely caustic, which is how it effects such a remarkable change in the cotton thread.
The treatment works by changing the structure of the cellulose molecules in the thread. That's why the process is only used on cotton, not on polyester and other synthetic fibers that don't contain cellulose (although it can be used on threads with a synthetic interior and a cotton exterior). In addition, the process causes cell walls to expand, making the thread look shinier and feel softer to the touch.
After the strong alkalinity of the treatment bath, a more acidic substance is used for neutralizing (so the thread doesn't stay caustic).
The next step is to dye the thread, taking advantage of the superior dye uptake that the treated fibers now possess. In fact, mercerizing can help the cotton take up about 25% extra dye, which enriches the hues and gives a wider range of possible colors.
So there you have it: the process for making mercerized cotton thread. In addition to the benefits of extra shine and richer colors, mercerizing also helps fabric hold on to the dye better (less bleeding and fading in the wash) and transmits a number of other benefits, such as enhanced mildew resistance. To learn more about thread, contact a company like WEST port.