Thread Myths Quilters Still Believe

A note on sources: much of the published evidence here comes from thread makers, and makers have products to sell. Superior Threads, the most-quoted source below, sells both cotton and polyester thread. Where we rely on a single maker, we say whose position it is.

1. "Polyester thread cuts cotton fabric"

The myth: polyester thread is harder than cotton fabric, so over time the stitches will saw through a cotton quilt.

What the evidence says: Superior Threads calls this "absolutely not true." Its argument is about strength, not fiber. When a thread tears through fabric, Superior says, it's because the thread "won the strength contest": under heavy use and stress, the strongest component in the quilt wins. A polyester thread that is much stronger than the fabric could do that under extreme use, but so could a strong glazed cotton. Superior says some glazed cotton threads are stronger and more abrasive than polyester.

Superior also points to clothing. Most cotton garments, including T-shirts, are sewn with polyester thread, and Superior notes you rarely see the fabric wear away around those seams. Its one exception is nylon, which it says goes brittle and discolors over time.

2. "Match the thread fiber to the fabric"

The myth: cotton fabric needs cotton thread so the two shrink and age together.

What the evidence says: Superior's view is that the cotton-only rule comes from tradition. Earlier generations of quilters used cotton thread because it was what they had, and the habit was handed down. On shrinkage, Superior says quality fabrics are mostly pre-treated and don't shrink the way they once did, and that a woven cotton fabric and a twisted cotton thread wouldn't shrink by the same amount anyway. It also says a machine should run any high-quality thread with the right needle and tension, and that quality matters more than fiber type.

There are still good reasons to choose cotton. Superior recommends cotton for piecing because it stands up to high-heat ironing, and cotton has a little grab that helps seams hold. Or you may simply like it. As Superior puts it, using cotton because it's tradition isn't a good reason, but using it because you like it is a great one.

3. "Old thread is fine"

The myth: thread doesn't go off, so a stash from decades ago, or a box of spools from a relative's sewing room, is as good as new.

What the evidence says: it depends on the fiber, the age and the storage. Cotton is a natural fiber and degrades over time. Superior says that even the best cotton thread of a generation ago lacked today's processing, and that it would probably be best not to sew or quilt with it. It expects today's high-quality cotton to be usable for decades, and it says modern cotton and silk will last "perhaps almost as long" as synthetics.

Polyester holds up better. Superior says polyester's color may fade with years of sunlight, but there's no evidence it deteriorates the way cotton does. On its storage page it goes further and says polyester can last more than 100 years. Storage matters for every fiber: Superior warns that long exposure to sunlight, especially UV, can fade colors and make some threads brittle.

4. "Expensive thread won't lint"

The myth: pay more and you get a lint-free thread; buy cheap and you'll be cleaning your bobbin area every hour.

What the evidence says: there's a link between price and lint, but it runs through how the thread is made. For cotton, the big factor is staple length, the length of the individual fibers. Superior sorts cotton into three grades: regular (short) staple, which it says makes linty, weaker thread; long staple, with less lint; and extra-long staple, the highest grade. Longer fibers mean fewer loose ends to shed. Processing matters too. Gassed thread, also called silk-finish or polished cotton, has been passed through a flame to burn off loose fibers, which leaves it smoother and lower in lint.

Fiber construction matters as much as fiber. Superior rates filament polyester as lint-free, core-spun polyester as low to moderate, and spun polyester, the cheapest kind, as moderate to high. Cotton ranges from low to high depending on staple and processing. Better cotton does tend to cost more, which is where the myth comes from, but a premium price on its own tells you little. Makers of premium threads make their own claims: Aurifil, for example, describes its mercerized cotton as producing virtually no lint.

5. "Cotton thread is always weaker"

The myth: polyester is the strong thread and cotton is the weak one, so any polyester will outlast any cotton.

What the evidence says: Superior, which sells both, says it "is not accurate" to call polyester stronger than cotton. It describes a widely sold 100% cotton quilting thread that, thanks to a glaze coating, tested twice as strong as a comparable polyester and beat same-size polyester, rayon and metallic threads. Cotton's strength also varies with quality. Superior says longer staples make stronger thread, and mercerizing, which nearly all sewing cotton gets, also adds strength.

Polyester varies as well. Superior rates spun polyester weaker than filament or core-spun, and filament weaker than core-spun at the same size. Ply count isn't a guarantee either: Superior says a well-made 2-ply can be stronger than a low-quality 3-ply.

6. "Rayon thread can't be washed"

The myth: rayon embroidery thread is for wall hangings only, because it fades, bleeds or falls apart in the wash.

What the evidence says: Sulky, which makes both rayon and polyester embroidery thread, says the two "wash and wear equally well, even in hot water." Its caveat is that polyester is the better choice for items that will see chlorine bleach or constant sun. Superior is more cautious. It says rayon is often not colorfast, with dye that can bleed when exposed to strong detergent, UV light or bleach, and that rayon is less strong and less durable than polyester. Sulky's answer on strength is that decorative stitching colors in a design rather than holding a seam, so the difference rarely matters.

Colorfastness varies by brand and even by color, so the maker's care notes are the thing to follow. Rayon embroidery thread is made by Sulky, Madeira, Robison-Anton and Gütermann, among others.

7. "Top and bobbin thread must match"

The myth: the bobbin must hold exactly the same thread as the top, or the stitches won't form properly.

What the evidence says: Superior says it's "not a problem" to mix fiber types, such as cotton on top and polyester in the bobbin, or weights, such as 40wt on top and 50wt below. Its tension guide explains that machines are factory-set for even stitches with a 50 or 60wt thread. Identical top and bobbin threads may need no adjustment, while mixed threads usually need a tension change. A thick 30wt polyester on top of a fine 60wt cotton, for example, will probably need the top tension loosened.

Sometimes a mismatch is the better choice. Superior suggests a smooth polyester bobbin under decorative threads such as metallics, and it advises against MonoPoly in both the top and bobbin, which can be too slick. Matching has its uses too. In machine embroidery, Sulky says matching the bobbin to the top thread takes more time but hides the occasional bobbin pull-up.

The myths at a glance

How to test your own thread

You don't need a lab to check an old spool. Superior describes a snap test for this:

1. Unwind 6 to 12 inches of thread.
2. Hold it firmly in both hands with the length between them.
3. Pull your hands apart until the thread breaks.
4. Judge the break. A clean, crisp snap means the thread is still good. If the thread seems to drift apart, like pulling a cotton ball apart, throw it out.

Superior says thread that fails this test will be hard to stitch with and will break often. The test was written with cotton in mind. Filament polyester is made to stretch and recover, so expect some give before it breaks. That is normal, not a sign of age.

A common extra step, not one from a maker, is to sew a sample. Stitch a few inches on scrap fabric with the thread and needle you plan to use, then tug the seam. If the thread passes the snap test but frays or breaks in the machine, the needle may be the problem, not the thread.

Storing thread so it lasts

Superior's storage advice is short: keep thread out of direct sunlight and away from air vents. UV can fade colors and make some threads brittle over time, and vents blow dust onto open spools. The fibers themselves don't suffer much from dust, but it comes off in the tension discs and builds up inside the machine. A drawer, closet, or closed plastic case or tub all work.

Common quilting advice adds a few more habits. Keep thread somewhere cool and dry, away from damp basements, hot attics and radiators. Note the purchase date on the spool, and use older thread first. We haven't found a thread maker that publishes a shelf life or an ideal humidity, so treat these as sensible habits rather than rules.

FAQ

Looking for a specific brand? Browse Superior Threads, Aurifil, and every other thread maker in our thread directory.

Related guides

• Thread Weights Explained — what wt, Tex and 50/3 mean on a label.
• The Best Thread for Quilting, by Task — a fiber, weight and needle for each quilting job.
• Thread and Needle Chart — which needle size and type suits each thread.
• Hand Embroidery Thread Guide — floss, perle, sashiko, hand quilting, wool and silk threads, and the needle for each.
• Thread brands on QuiltMap — every thread maker in our directory.

Sources

1. Superior Threads, "Quilting Myths": superiorthreads.com/education/quilting-myths
2. Superior Threads, "Polyester Thread Strength": superiorthreads.com/education/polyester-thread-strength
3. Superior Threads, "Thread FAQ": superiorthreads.com/education/thread-faq
4. Superior Threads, "Thread Storage": superiorthreads.com/education/thread-storage
5. Superior Threads, "Thread Characteristics": superiorthreads.com/education/thread-characteristics
6. Superior Threads, "Tension Guide": superiorthreads.com/education/tension-guide
7. Superior Threads, "Thread Selection Chart" (PDF, 10/2016): thread-selection-guide.pdf
8. Sulky, "Machine Embroidery Series: Rayon vs. Polyester": blog.sulky.com/machine-embroidery-series-rayon-vs-polyester/
9. Aurifil, Thread FAQ: aurifil.com/aurifil-thread-faq