Know Your Thread Types: Cotton, Polyester, and Polycotton

We examine the different thread types and their pros and cons in our complete guide to cotton, polyester, and polycotton threads.

Lucas Cooper

Thread is not only essential in holding your garments together. It can also be accented for contrast, used for a repair, or create visual detail in a garment, like the arcs on a pair of jeans.

While there are many types of threads in today’s garment world, there are a few types that stand out for denim production. The chain stitching station at Berlin’s DC4 (see below) has dozens of threads on hand to ensure the perfect match for the jeans they hem. But each material ignites the age-old battle of authenticity vs. modern era durability.

In this article, we’ll be looking at a few different types of thread: 100% Cotton, 100% Polyester, and Polyester Core/Cotton Wrap. Read on as we look into the history, pros, and cons of each type!

100% Cotton Thread

Cotton thread has been used practically since the dawn of human history. Traces of cotton thread have been dated back to 7000 years ago, but it wasn’t until the year 1730 that cotton thread was first spun by machines. From then on, it has been a staple of garment construction.

Thanks to the natural fibers, cotton thread has excellent sewability with little kinking or skip stitching, and it’s rarely affected by hot needles (a common element of high-speed sewing machines), so the cotton will not melt and will even sew well on poorly adjusted machines. Also, cotton thread only increases in strength when wet.

Most 100% cotton thread will go through a Mercerizing process, where the thread is treated under tension in a solution of caustic soda, which makes the cotton fibers more uniform. This process causes the fibers to swell, resulting in the thread accepting dyes more readily. This process also enhances luster and increases the thread’s strength and tenacity.

While cotton thread has been around for a while, it does have its drawbacks. Natural fibers are generally not as uniform as synthetic ones and can be affected by the elements. Although cotton thread will become stronger when wet, it can also shrink and mildew. Compared to polyester or poly/cotton threads, their strength and resistance to abrasion are inferior. It has little “give” or elasticity and can break easily if used on a seam with a lot of stress.

Reproduction companies such as TCB and The Real McCoy’s have used cotton thread because of its heritage and authenticity. And while cotton thread may not be the strongest or most durable, there is something to be said about the history behind it. It should also be noted that cotton threads are typically biodegradable, so if paired with a cotton fabric, it makes the garment a lot more environmentally friendly.

TCB Late 1940s Selvedge Denim Jeans, made to 1940s specs including 100% cotton thread, available for $309 from Redcast Heritage.

100% Polyester Thread

Polyester fibers were invented by British chemists J. R. Whinfield and J.T. Dickson in 1941, but the actual licensed production of Polyester threads wasn’t until 1955. These synthetic threads have a few superior properties over a natural cotton thread.

The production process is obviously much more complicated than spinning a natural fiber. Polyester petroleum byproduct that comes from xylene, a hydrocarbon compound that’s generated during the cracking process of crude oil. Nitric acid and glycol are added to modify the xylene. The fluid is heated and condensed in an autoclave, and the molecules align to form long molecules called polyester. The polyester is then extruded, cooled, and then cut into chips to be later spun into filaments.

Up to 170,000 filaments band together to create what’s called a “tow”. This Tow is then stretched and spun until the fibers have been stretched up to 10-20 times their original length. Voila—polyester thread!

Due to the spinning process of the polyester, the thread has a much higher strength and greater elasticity than its natural counterparts. This makes polyester thread a better choice for stretch knit fabrics. The thread is also more resistant to abrasion, mildew, and sunlight than cotton. The downside, however, is that polyester thread is generally thicker, kinks more easily, and will melt at high temperatures. It is also not biodegradable or renewable; therefore, it has a harsher environmental impact.

Brands such as 3sixteen and Brave Star Selvage have used 100% polyester threads in their jeans for the greatest durability.

Brave Star Selvage Mojave Western Cut 16.5oz Sensei Japan Selvage Denim, available for $158 from Brave Star Selvage.

Polyester Core, Cotton Wrap Thread (AKA Polycotton)

While polyester thread has become more and more popular for its toughness, many have started using a thread that keeps the authentic look and feel of cotton, while maintaining the strength of polyester; polycotton!

This kind of thread is made up of a 100% polyester core filament, wrapped in a 100% cotton staple wrapper. With the combination of both cotton and polyester, you get the best of both worlds. The cotton wrap gives the thread the sewability, authentic look and feel, and heat resistance you would get with 100% cotton. The polyester core gives the thread durability, stretch, and resistance to abrasion of a 100% polyester thread.

Polyester/cotton thread has become increasingly more popular in denim garment production. Companies such as Rogue Territory and Iron Heart are using polycotton thread for its authentic look, feel, and aging properties, while still keeping the structural durability with the polyester core.

Iron Heart 555 17oz Selvedge Denim Slim Cut Jeans – Natural Indigo, available for $384 from Iron Heart.

Pros & Cons of Thread Types

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