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Writer's pictureHeidi Sapere

Top 2 Sewing Threads: Cotton vs. Polyester

Updated: Jun 29, 2023


Sheep Show Quilt

Top 2 Sewing threads:

Should I use cotton or polyester for my project?


Cotton and polyester threads have distinct characteristics that make them suitable for various projects.


#1 thread rule to remember: Cotton thread with natural fabrics. Polyester thread with synthetic materials.


What is cotton thread?

Cotton thread is a natural fiber that originates from the cotton plant. It is known for its longevity, which makes it ideal for heavy-duty projects like quilting, denim, and canvas. It is also perfect for sewing natural fabrics such as silk and cotton as it sinks into the natural fiber material, unlike polyester, which will sit on top. Because it is a natural fiber and heat-resistant, cotton will not melt in the microwave like polyester when doing projects like microwavable bowl cozies. The cotton thread also has a matte finish, making it excellent for sewing garments with a flat or matte appearance. It is also eco-friendly because it is biodegradable, which may be considered when making natural cotton napkins or unpaper products you compost later when they become well-loved—a consideration for sustainability.


What is polyester thread?

Polyester thread is a synthetic fiber that is produced from petroleum. This thread is also known as "universal" thread because it works well on all fabrics and can be cheaper than cotton. Polyester thread can also have a shiny finish, making it perfect for sewing garments with a lustrous appearance. It is incredibly robust and considered stronger than cotton thread, making it capable of enduring stress without stretching or breaking. Polyester also has more stretch to it when using stretchy fabrics and for any synthetic, plastic, and lycra material. It can resist chemicals, UV rays, and abrasion, making it ideal for outdoor and industrial projects where exposure to harsh environments would occur, such as in window curtains, outdoor patio furniture, and hiking gear.


When selecting between cotton and polyester thread, consider the type of project you are working on. Remember, a good rule of thumb is: natural fiber with natural fiber, plastic with plastic. When in doubt, a polyester thread will be your go-to universal thread that works with all fabrics. Ultimately, both thread types have advantages and disadvantages, so it is up to you to determine which will work best. If you are quilting, the polyester thread will sit on top of your cotton fabric, whereas cotton thread will sink in. Polyester will hold up better on outside items and overall wear, and cotton is biodegradable, natural, and heat resistant.



What thread do I use in my machine and why? Cotton or Polyester?

Regarding my artistic creations, such as quilts, bags, and boxes, I have found that my choice of thread is primarily based on color rather than the type of thread. While I have not noticed a significant difference in the use of either polyester or cotton thread for piecing fabric or top stitching, I do have friends who adamantly swear by using cotton thread exclusively for their quilting projects.


Occasionally, I find that my options for thread color and size of the spool are limited to cotton or polyester when visiting my local sewing shop. For example, they only offer cotton thread when I purchase Gutermann variegated mega spools at Joann Fabrics. While I prefer a more robust polyester alternative, I am forced to settle for cotton thread due to limited options. I typically use a variegated thread for quilt labels, top stitching, quilting my quilts, or decorative stitches, and I believe that polyester thread would result in less breakage than cotton. Nevertheless, cotton thread still holds up remarkably well, especially when I switch to a topstitch needle.




When painting veils:

In the past, when I created silk veils that required the edge to be sewn under, I exclusively utilized cotton "silk-finish" thread. I avoided polyester thread because it would lie on the fabric instead of sinking into it. "Silk-finish" refers to the cotton thread's silk-like shine. I did not know the difference between thread types, so I asked another sewer in the store. She told me to only use cotton "silk-finish" thread on my veils, so I did!


What thickness of sewing thread should be used?

What do the thread numbers mean?


#1 rule: Universally, the thread weight should be 50wt or 60wt for most medium-weight fabrics. Heavy fabrics like denim, upholstery, or denim topstitching 30wt. Lightweight silks 70-80wt.


Sewing can be frustrating if the wrong materials, including sewing threads, are used. Our fabric pieces would fall apart without the right thread, so choosing the right thickness for your project is crucial.


Understanding the ticket system can help you choose the right thread for your sewing project. The ticket system is a numbering system used to indicate the thickness of the thread. The higher the number, the thinner the thread; the lower the number, the thicker the thread. For example, a thread with a number of 30 is thicker than one with a number of 50.


When choosing thread for your sewing machine, you'll want to use a thinner line with a higher number for lightweight materials such as chiffon or silk. This will prevent your stitches from being too bulky and visible. For heavier fabrics such as denim or canvas, you'll want to use a thicker thread with a lower number. This will ensure your stitches are strong enough to hold the fabric together.

Once again: Higher number thinner thread. Lower number thicker thread.


As I remember: The heavier the fabric, the more the garment will sink; therefore, it needs a smaller number to keep it afloat. The lighter the material, the more it will float, so needs a bigger number to keep the garment ground.


What thickness of sewing thread do I use in my sewing machine?

Regarding thread thickness, I use 60wt, also known as "universal" thread, for 98% of my sewing projects. Even when making veils, I wasn't aware of the various thread weights, so I stuck with the trusty "universal" weight. I do not often work with fabrics of different weights, but my top sewing rule is to choose a 50-60wt thread that securely holds the fabric together without breaking while sewing. Usually, the 50-60wt thread works great.


Please comment or email me with any other questions you have about sewing thread. Happy sewing!

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