Cotton is the thread of choice for many seamstresses because of its softness, durability, flexibility and the nearly endless rainbow of colors available. Because there are so many different types of thread on the market these days, choosing the best thread can be a bewildering task. The choice of cotton thread depends on the intended purpose, be it hand or machine embroidery, quilting, tailoring or appliqué. The choice, however, is often simply a matter of personal preference.
Mercerized Cotton Thread
Mercerization is the process of subjecting cotton thread to a chemical process in which the thread is dipped in a sodium hydroxide bath, followed by an acid bath. The chemical treatment causes the thread to plump up before it relaxes and straightens once again. Mercerized thread more readily accepts dye and holds the color longer. It is also stronger than nonmercerized thread, has a shiny appearance and resists mildew. Most modern commercial cotton threads are mercerized.
Glazed Cotton Thread
Glazed thread is mercerized cotton thread that has been waxed or treated with various chemicals that give it a polished, lustrous appearance, which is desirable for certain hand-sewing and hand-quilting projects. Although the process of glazing strengthens the thread, the glaze often can rub off and clog up sewing machines and sewing machine needles. For this reason, most stitchers will avoid glazed cotton thread for machine sewing.
Gassed Cotton Thread
Gassed thread is mercerized cotton thread that has been exposed very rapidly to a hot gas flame. This process removes the fuzz and excess lint on the thread, giving it a brighter, smoother, slightly iridescent appearance. Gassed cotton threads are more expensive than regular mercerized cotton, although gassed thread manufactured in America will be considerably less expensive than Egyptian cotton. Gassed thread is often used in fabrics such as poplin, voile and gabardine, but its high quality makes it useful for most types of sewing or quilting.
Cotton-Wrapped Polyester Thread
Cotton-wrapped polyester thread is an all-purpose thread often referred to as "dual duty." It is practical for nearly any sewing project, both by hand and machine, and is especially useful for blended fabrics. It is stronger than than 100 percent cotton thread. It is also more elastic, which can sometimes be undesirable, but can be useful for sewing fabrics that stretch. Lower grades of cotton-wrapped polyester thread can become fuzzy, which can lead to breakage of the thread and a build up of lint in sewing machines.
High-quality mercerized cotton threads are soft and durable enough to adjust to normal wear and tear, but pliable enough to withstand typical fabric shrinkage. It is an easy-care fiber that can be hand or machine washed and air or machine dried, although hand washing and air drying will preserve the life of the thread. Cotton thread is available in a variety of weights that make it desirable for a number of different sewing projects.