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Thread Of Truth.

Aug 11th 2021

At the most recent guild meeting, we discussed a few places to find more information about thread. We are including a link to "A Thread of Truth" by YLI as well as another shorter document.

Quilts on the Corner is your home for quality threads!


Understanding Thread Weight: The weight or size of thread is an important consideration for any sewing project. Making proper adjustments relative to different thread weights will make sewing, quilting, or embroidery projects more enjoyable. The most common methods of measurement of threads are weight, denier, tex, and number.

Weight: A smaller weight number indicates a heavier thread. The weight of a thread is actually a length measurement. Dividing the length of thread by a set weight derives the exact measurement of a thread weight. A thread is labeled 40 wt. when 40 kilometers of that thread weighs 1 kilogram. A 30 wt. thread is heavier because it takes only 30 kilometers of thread to weigh one kilogram.

Denier: Weight in grams of 9000 meters of thread. If 9,000 meters weighs 120 grams, it is a 120-denier thread. Many polyester and rayon embroidery threads are 120/2, which equals 2 strands of 120-denier thread for a 240 denier total. Larger denier numbers are heavier threads.

Tex: Weight in grams of 1000 meters of thread. If 1,000 meters weighs 25 grams, it is a tex 25. Larger tex numbers are heavier threads.

Number System: The Number standard is used on many thinner threads and is written as No. 50 (or #50) or No. 100 (or #100). Many people confuse this with a Weight measurement and incorrectly suppose a No. 100 thread is a 100 weight thread. The Number standard was developed in Japan and is known as the Gunze Count system. The smaller the number, the heavier the thread. It is not necessary to know the exact conversion formula. Just remember that a spool of thread stamped with No. 100 does not mean it is a 100 weight thread. One spool of thread may be stamped No. 50, another spool may be stamped 50 wt., and yet another spool of thread may be stamped 50/3. All three of these are measured using different standards and we must not assume they are similar in size. When comparing threads, make sure you use a consistent standard of measurement and the best reference is your eyes and fingers to gauge the diameter of thread.

A basic conversion chart for understanding thread measurements:

  • Weight to Denier 9000/weight
  • Weight to Tex 1000/weight
  • Denier to Weight 9000/denier
  • Denier to Tex denier x 0.111
  • Tex to Denier tex x 9
  • Tex to Weight 1000/tex
  • 40 weight = 225 denier = Tex 25
  • 3000.jpg
Thread Colors


Thread tension on most machines is applied to the thread as it passes between a pair of tension disks. Increased pressure on the tension spring increases thread tension. When a 40 wt. thread is replaced by a heavier 30 wt. thread, the increased diameter pushes the tension disks further apart, increasing pressure on the tension spring. Just by increasing (or decreasing) the diameter of our thread, we have increased or decreased the thread tension. If the tension is too high, it damages the thread and the thread can break. If it is too low, the thread will loop on the back of the fabric. When you change threads, remember to take the diameter of the new thread into consideration and make adjustments as necessary. Some longarm machines use Rotary Tension instead and have less risk of breakage when changing thread sizes because they are not pinched between two disks, but instead adjust the thread tension by changing the tension on the spin of the tension assembly.

How does tension affect the outcome of a stitch?

If the top and bottom threads are identical in fiber and weight, adjustments may be minor. However, if we use cotton thread on top and polyester thread underneath, or metallic thread on top and polyester thread underneath, or a heavy thread on top and a fine thread underneath, it is necessary to carefully adjust the tension settings. It is perfectly OK to use different thread types and weights on the top and bottom.

Think of the top and bottom thread as having a tug of war. If both top and bottom threads are balanced, they should produce perfectly even stitches with no top thread showing underneath and no bobbin thread showing on top. However, in the real world, the teams are rarely equal. One team will be stronger or bigger or faster than the other. We often use different fibers for the top and bottom threads. We also add stabilizer or batting. All these factors make it necessary to adjust the tension for each project. By adjusting the top tension either up (increasing tension) or down (decreasing tension), we are able to add or take away strength on the top thread team to equalize the tug of war.

What most commonly affects stitch balance?

Batting: Batting adds drag on the top thread. Depending on the loft and density, batting can put more stress on the thread during stitch formation. This results in an increase of stress applied to the top thread. Cotton batting tends to grab the thread more than polyester batting, adding more friction on the thread.

Fabric: If you are sewing on a densely-woven fabric, such as batiks, duck cloth, or denim, the top thread will be exposed to a greater degree of friction. Fabrics that have a looser weave, such as quilting cotton and knits allow for the top thread to pass through the individual fibers in the fabric with less friction, and thus with less tension applied to the thread during stitch formation.

Top Thread: The thickness and material of the top thread can affect stitch quality and stitch balance. If the top thread is a thick, 30 wt. polyester thread and the bobbin thread is a fine, 60 wt. cotton thread, the top tension will most likely need to be adjusted (loosened) to accommodate an even stitch. It is not a problem to mix fiber types, cotton thread on top and polyester thread in the bobbin, or thickness, 40 wt. thread on top and a 50 wt. thread in the bobbin. Some threads require very loose tension in order to achieve balanced stitches. Metallic thread, for example, is a beautiful decorative thread. However, it is not as strong as a 40 wt. polyester quilting thread and will need the top tension reduced. When the appropriate tension adjustments are made, you can use a mixture of threads and obtain balanced stitches.

Bobbin Thread: Cotton threads tend to have more grab to them compared to a smooth, filament polyester thread. Sometimes, a thread with a little grab is preferred, such as when piecing a quilt together. When topstitching a quilt, a smooth bobbin thread may be preferred, especially when quilting with decorative threads like metallic.

We've created an easy-to-understand diagram to help illustrate the thread tug of war. By keeping the top and bottom thread in balance, you will mitigate problems with broken and uneven stitches, allowing you to spend more time sewing and quilting with less time troubleshooting problems that arise from uneven tension.

Quilt Sandwich Tension: If the layers of the quilt are too tight, the stitches can’t sink in and it won’t make a good looking stitch. If the layers are too tight, the needle will flex too much and may cause shredded thread, broken needles and poor stitches.

Summary: In summary, the most common method used to gauge the diameter of threads today is the weight system. While the weight system is not an exact science, it is recognized as being the most popular for quilters. While you may have a favorite thread for different purposes, you can always mix and match thread types and brands to achieve your quilting goals! Once you have a favorite or go-to thread that you commonly use, this thread can be your benchmark when comparing different threads.
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