Thread Labels - What Are They Telling You?

Have you ever wondered what your thread label was telling you? I know I have! There's so many tiny numbers and little words crammed onto that one sticker, no wonder why we are left with so many questions! The thread label will tell you all about the quality and reliability of the thread. Remember when comparing thread labels, it is best to compare cotton to cotton, polyester to polyester, silk to silk, etc.

Here's some of the things you will find on a thread label.

Thickness/Weight: Thread thickness is typically written as a # sign followed by a number. You will often hear others refer to the thickness as weight and can be written with two numbers and "wt". For quilting and embroidery thread, the smaller the number, the thicker the thread. The larger the number, the thinner the thread. #40 (40 wt) is much thicker than a #60 (60 wt).

Tex: This is an accurate measurement and is considered a direct numbering system. Meaning the higher the tex number, the heavier the thread. Tex standard uses 1,000 meters of thread per gram. (1,000 meters of thread weighs 1 gram = Tex 1)

Fine: Tex 9 to Tex 20

Medium: Tex 21 to Tex 70

Heavy: Tex 71+

Denier: A denier is a unit of measurement that expresses fiber thickness of individual threads or filaments in fabric or textiles. This is done by using a single strand of silk as a reference for one denier where 9000m of the strand would equal one gram. 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.

Ply: Ply refers to the number of individual strands twisted together to make the thread. The number of piles contributes to the strength of the thread. Most thread that is used for quilting, embroidery, or sewing is either 2 or 3-ply.

Mercerized: Today, most cotton threads are mercerized. Mercerizing is a process of treating cotton thread with a solution, causing the fibers to swell. this allows the dye to better penetrate fibers increasing its luster. 

Unmercerized (soft): The fibers are left untreated and remain in their natural form (relatively speaking, of course). An unmercerized thread is very absorbent, making it more ideal for towels, dishcloths, etc.

Fire Retardant: This thread is able to withstand extreme heat. The special coating is essential for firefighting gear and race car suits. It’s even used in children’s bedding and mattresses.

Bonded: Bonded thread has a special resin applied to create a tough, but smooth, protective casing. This is most often applied to nylon and polyester thread with multiple filaments, like corespun polyester and smooth multifilament thread.

Glazed: Glazed thread is a type of thread which has been coated with either wax, starch, resin, or other chemicals. This results in a smooth, glossy thread with a hard finish. Glazed thread is quite a bit stiffer than unglazed thread and has a wire-like look and feel. Glazed cotton threads are recommended for hand quilting only. You do not want the wax coating of a glazed thread running through the tension discs of your sewing machine. Many glazed threads are not usually labeled as such. To check whether or not a cotton thread is glazed or not, unwind a two-three foot section from the spool and if the thread twists like a telephone cord, it’s glazed.

Gassed: One step of the processing of high quality cotton threads is to pass the thread at high rate of speed, over a flame. This process burns the excess fuzz to create a higher sheen. Not all threads are gassed, and you can tell by the excessive amount of fuzz or hairs the thread has. Other terms used for gassed cotton are polished cotton and silk finish cotton.

Staple length: The individual fiber of a cotton boll. We commonly refer to staple in the sense of the length of the individual cotton fiber. The longer the staple, the stronger the thread. If there is no mention of the staple length, assume it is regular (or short) staple thread. Long staple is better than short/regular staple and extra-long staple is the best. If a cotton thread is extra-long staple, the label will proudly state that fact.

Twist Direction: The direction the thread is spun defines its twist. It can either be twisted in a ‘Z’ direction (left twist) or a ‘S’ direction (right twist). A ‘Z’ twist is suitable for single needle sewing machines. A ‘S’ twist thread isn’t commonly used in home sewing machines.

Thread Direction: On most domestic sewing machines, there is typically two places to place the cone/spool of thread. If the thread is cross-wound (which means the thread comes off the spool from the top), use the horizontal spool pin. If the thread is stacked (which means the thread comes off the spool from the side), use the vertical spool pin!