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Thread Primer for Sewing Machines

I've finally gone ahead and written down the talk I gave about threads when I taught New Owner classes for the Bernina at NorthWest Sewing in Seattle.

Determining Thread Quality

Using good quality thread is important! Thread quite literally holds your sewing project together. Poor quality thread is lumpy bumpy with thick and thin spots, jerks through your machine's tension disks causing ugly stitches, and is more likely to break and cause trouble. Poor quality thread can make sewing a nightmare. Good quality thread is smooth, has a uniform thickness and sails through your machine with nary a problem.

To check thread quality, unspool about 18 inches of thread and look for the following:

Does your thread have random bits of fluff or lint along it's length? Lint gums up your tension disks, which can cause missed stitches, and will increase the frequency with which you need to clean your machine.

A couple side notes:

  • Cotton thread will always have a little more lint than polyester thread.
  • Wool threads for crewel work are uniformly fuzzy by definition - this is not a sign of poor quality.

Check for thick/thin patches. Uniform thickness is important because threads with thick/thin patches can cause puckered seam lines, skipped stitches or thread breakage. Your machine's tension disks have no way to adjust to the variations in the thread's thickness. This means that as the thread goes thicker/thinner, your machine's tension disks go tighter/looser.

It is also important to use the right thread for the job - rayon embroidery thread may be beautiful, but it will never hold up in a seam line. In Thread Types below, I talk about the right thread for the job, but it helps if you understand Thread Weights, first.

Thread Weights

Thread weights are NOT standard. Each manufacturer creates their own interpretations. That said, thread weights provide useful guidelines. In general, thread gets thicker as the number of the weight gets smaller. So, a 100 weight thread will always be finer than a 12 weight thread.

  • 12 weight - the thickest thread commonly used in the top of the machine. Used for embellishing or heavy topstitching.
  • 30 - 40 weight - standard weights for most machine embroidery threads.
  • 50 weight - standard weight for cotton construction threads. May be either 2 or 3 ply (listed as 50/2 or 50/3).
  • 60 or 70 weight - cotton thread for darning and heirloom stitching. Bottom Line polyester bobbin thread.
  • 100 weight - standard weight for polyester construction threads.
  • 120 weight - polyester bobbin thread for machine embroidery.

Thread Types

While there are an incredible number of choices in today's thread market, I generally divide my threads into two categories based upon how I use them. There are Construction threads, which are designed to hold seams together. And there are Embellishment threads, whose main purpose in life is to lay on the surface and look pretty.

Construction Threads hold seams together.
Construction thread is strong and relatively thin. It may be made from cotton, polyester, cotton/polyester blends or silk.

I prefer to use cotton construction thread when I am working with natural fibers (including rayon which is a man-made, natural fiber from wood pulp).

When working with man-made fibers such as polyester and nylon I use polyester construction thread. Polyester construction thread is very thin, and incredibly strong.

Note: This strength is actually why quilt conservators do not recommend polyester thread for piecing or quilting. Polyester thread too strong compared to the cotton fabrics used in piecing a quilt. The thread can act as a saw in the seam lines, slowly cutting through the fabric.

My favorite construction threads include Mettler's Silk Finish Egygtian cotton and Metrosene polyester. Madeira's Aerofil polyester is also very nice.

Thread for Embellishing lays on the surface and look pretty.
Some embellishment threads are plenty strong enough to hold seams together, but that is not their primary purpose. Embellishment threads are typically thicker than construction threads and have a higher luster. Because they are thicker, embellishment threads fill the surface more quickly, and a single line is much bolder and more visible.

Embellishment threads are most commonly made from rayon, polyester and cotton.

Rayon was the first mass-marketed embellishment thread.

  • Rayon typically comes in 30 and 40 weights.
  • Rayon is a dream to work with. They have huge color ranges, amazing sheen and creates a beautiful satin stitch.
  • Unfortunately, rayon is also the most fragile of the embellishment threads. Rayon is up to 50 percent weaker when it is wet than when it is dry. Therefore, rayon is probably not the best choice for embellishing swimsuits and children's clothing.
  • My favorite rayon embroidery thread is made by Robison Anton.

Cotton embroidery threads have the softest sheen. I use cotton embroidery threads when working with heirloom, ethnic or folk designs where the high sheen of rayon or polyester might look out of place.

  • Cotton thread comes in the widest range of weights:
    • 60 weight cotton embroidery is used for heirloom work and darning.
    • 30 weight for standard embroidery.
    • 12 weight for thick lines of stitching.
  • My favorite cotton embellishment threads are Sulky's 12 Weight Cotton (both the solids and Blendables) and the 30 wt Cotona by Madeira.

Polyester embellishment threads started out as the "red-haired step child" of the embellishment line. Today's polyester embroidery threads have a good sheen, perhaps a little sharper than rayon's, and a great color range.

  • Polyester threads typically come in 40 weight, though 30 & 35 weights are also available.
  • Polyester threads have a memory, and may not lie quite as nicely in satin stitching.
  • They are extremely strong, and bleach resistant. This makes them ideal for embellishing exercise wear or children's garments which will be wet or washed often.
  • However, polyester threads can be a little scratchy, especially when compared to rayon
  • Superior Threads makes my favorite polyester embellishment threads. They have a great line called "Rainbows", variegated threads with fun color combinations and a very short color change.

Metallic threads are always embellishment threads. Do not use metallic threads for construction purposes! Metallic threads may be made from actual metal, polyester, metal with a polyester core or from Mylar.

Some tips for using metallic threads:

  • Always use the upright spool pin on your sewing machine. Metallic spools need to spin as the thread unspools. This helps prevent the thread from twisting which can cause thread breakage.
  • Loosen the top tension slightly.
  • Use a needle with a larger eye. I prefer Topstitch needles when working with metallic threads. The Topstitch needles have the largest eye for their size.
  • Mylar threads work well for bobbin work even when you can't use them on top.

For metallic threads, my favorites are Yenmet Thread and FS Jewel "Black Core" by Madiera. Yenmet's thread was designed to run in high-speed industrial machines without breaking, tangling or shredding. It works equally well in home sewing machines. Both Yenmet and FS Jewel have incredible color lines, and both are completely different.

Where to find these threads:

All contents © Karen Williams unless otherwise noted
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Last Updated: January 18, 2012