Although matching thread fiber types to fabric fiber seems logical, choosing the appropriate thread by characteristics such as strength, colorfastness, or chemical resistance is more practical. For example, natural fiber threads such as cotton, linen, silk, and rayon (a manufactured fiber made from natural cellulose) sew beautifully. But synthetic fibers like polyester, nylon, or acrylic are stronger. This article is The Ultimate Sewing Thread Guide. It includes everything you need to know to choose the perfect thread for every sewing project. The guide is long, so I've also created a quick guide at the bottom.
Thread Types and Fibers
Thread is a thin, continuous cord made by either spinning staple thread fibers into single strands—or yarns—and then twisting two or more of them into a plied sewing thread or by an extrusion process that forms one or more long, continuous filaments. Once you understand the differences between the fibers, choosing the best thread for the job is easier.
Spinning is when staple fibers are twisted into single yarns, then plied together to form thread. Spun threads are soft, somewhat fuzzy, and have good sewability.
Long lengths of polyester, rayon, nylon, or silk are extruded mechanically (or by silkworms) as a single monofilament or as several strands in a multifilament. Filament circumference can be a shape other than round. For instance, the trilobal filament has three sides for improved light reflection.
Core-spun thread combines the strength of polyester with sewability or cotton. Polyester filament centers are wrapped with spun cotton or polyester fingers into strands that are twisted together to form a piled thread. The filament core adds strength, and the shorter fibers mimic 100% cotton thread. One downside to a core-spun thread is that it can produce lint.
Monofilament thread is a single strand of nylon or polyester filament. Polyester withstands higher heat than nylon. Almost invisible, it comes in clear, gray, or matte. It feels scratchy when worn next to the skin.
Types of Thread Fibers
Thread fiber is based on what the thread is made from, such as natural materials or synthetic.
Natural fibers come from plants or animals. The most common natural fibers are cotton, silk, and wool.
Made from spun staple cotton fibers (Egyptian long staples are about 1 1⁄4 inches long, and American Pima staples are about 1 1⁄2 inches long). Cotton thread has little stretch, limited strength, and (compared to other fibers) can produce a lot of lint. It also has a low sheen. Use cotton thread for heirloom sewing, decorative stitching or embroidery, sewing lightweight natural fibers, patchwork, and quilting.
Made from a natural continuous fiber that is strong, smooth, and has a lustrous sheen. It is wonderful for hand-sewing, tailoring, and basting. Lightweight silk threads work best for fragile sewing fabrics. Use medium-weight silk thread for elegant construction on delicate silk and wool fabrics. Opt for heavier-weight silk thread for buttonholes and hand- or machine-topstitching.
Wool fibers are graded by fineness, length, color, and appearance, fitness being the most important quality. Once the wool is sheared from the sheep, the fibers are cleaned, scoured, carded, and spun to make thread or yarn of various thicknesses. Wool threads are fuzzy. Wool is often blended with acrylic fibers for added strength.
Rayon thread is made from a continuous fiber, rayon thread has no stretch, very little strength, and is not always colorfast, but it tolerates high temperatures and is soft and beautiful. However, it is less durable than silk or polyester and is used almost exclusively for decorative stitching and machine embroidery—not recommended for construction.
Synthetic fibers are petroleum-based and engineered to provide specific attributes, such as strength and luster. Various chemicals are put into a liquid state and extruded through spinnerets to create strands, then twisted and processed into thread.
The garment industry often uses polyester thread because it is strong, colorfast, and resistant to UV rays, rot, mildew, and chemicals. In addition, it has some stretch, good recovery, and is heat-resistant.
• Spun polyester is made by cutting filaments into 4- to 5-inch staples, spinning them into yarns, and then plying them into a smoother and stronger thread than a spun natural fiber. Use it for all-purpose sewing.
• Trilobal filament polyester is plied, with multiple continuous filaments. The triangular filaments shine like rayon but have better colorfastness.
• Texturized polyester has the same characteristics as woolly nylon but tolerates higher temperatures.
Nylon thread is made from extruded filaments. One benefit of nylon thread is that it comes in various very strong and rot-resistant forms.
• Monofilament is a single filament and comes in a wide range of weights. Use a lightweight version for invisible sewing and blind hems, or encase a heavier version inside a rolled stitch to support fluted or ruffled edges.
• Texturized threads are continuous multifilaments that stretch into a fine, strong thread and expand to a full, fluffy appearance when relaxed. Use them for serged seams, decorative stitching, and rolled hems.
• Upholstery threads are often nylon. They come in limited colors, are extremely strong, and will withstand the rigors of outdoor use. Upholstery thread is easy to sew with, but the ends ravel and are challenging to knot.
Unfortunately, there isn't a universal sizing system for threads. This means there is no way to compare size among all types. However, understanding the three sizing systems used today is useful because it gives you an idea of relative size within a thread type.
Used for cotton and other spun threads—weight is expressed as the number of kilometers required of a specific thread to weigh 1 kilogram. The higher the number, the lighter and finer the 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
The importance of thread weight
The weight of thread influences several aspects of a quilt, article of clothing, embroidery design, or craft. Stitch density, area, or field density, needle size, and tension.projects, mainly field densities, needle size, and tension.
A slash separates weight from plies:
When there is a slash in the thread size, the first numeral indicates weight. The second is the number of plies in that thread. Thread marked 60/2 is a 60-weight, 2-ply thread. Generally, 2-ply threads are for machine-embroidery, and 3-ply threads are all-purpose.
Denier is used for man-made threads like polyester, rayon, and nylon. The higher the number, the heavier and thicker the thread. Denier is the weight in grams of 9,000 meters of a specific thread.
Previously used for industrial threads only, this system is expected to become universal tex is the weight in grams of 1,000 meters of a specific thread. The higher the number the heavier and thicker the thread.
Choosing the Right Thread
Aside from fabric, thread is perhaps the most essential sewing component, yet we often sew without considering our thread selection. We've all seen the jargon related to thread and wondered what it means. Since home sewers have a greater variety of threads to choose from than ever before, a basic knowledge of threads will reassure you as to what you need to know when you set out to make a selection and what's just fascinating.
Of course, selecting the right thread requires more than picking the best color for your fabric. For some projects, any of several thread choices may be equally acceptable. For others, the finished results are affected for better or worse by the type of thread used. The thread must perform well on your machine with your fabric and needle and give the look and wear you want.
To judge thread quality: Look and Touch.
Whatever thread you choose, always check its quality; inferior thread can leave a residue in your machine or clog it with lint. For general machine-sewing, I look for a smooth, nub-free strand that doesn't twist easily and is as free of fuzz as possible. I unroll a length, hold it toward a light, and look at it closely to judge a thread. Then, I feel for nubs and check that it's smooth and even with my fingertips.
Mail and Internet ordering has made most thread varieties readily accessible. Of course, it's impossible to check thread quality online, but if you provide a vendor with a self-addressed stamped envelope and request a sample length, he may accommodate you. Or you can purchase one spool and order more if it proves satisfactory.
After I've chosen a thread and before I commit to using it on my project, I test it on my fabrics. I experiment with stitches and stitch settings, presser foot and stabilizer varieties, and tension settings. I've learned to record these details right on the sample stitch-outs: too often, I've left a project and thought I'd remember the settings, only to realize I'd forgotten them when I returned.
Consider the use before making a choice.
We're often advised to match the thread fiber to the fabric fiber when possible, but I think there's more to a smart thread decision than that. Understanding the thread fiber characteristics allows me to pick a thread by the attributes I want for a particular project, letting fabric type, care, and use influence my choice.
For example, if my fabric requires high heat for pressing, I'll choose a thread fiber that also withstands the heat. If I'm constructing a heavy cotton denim bag, I'll select a polyester thread for its strength and durability rather than a weaker cotton thread. Similarly, most children's clothing requires a durable polyester thread to withstand rough wearing and heavy-duty washing and drying. For swimwear, choose a strong thread with stretch plus UV and chemical resistance—you don't want to risk fading your decorative stitching or rotting your seams in chlorinated water.
Where to Buy Thread
Amazon has a wide variety of different thread manufacturers. Gutterman thread is my favorite thread brand, but I also like Mettler, Superior Threads, and Coats & Clark when I can't find what I need in the Gutterman line. Of course, thread can also be purchased at local fabric and craft stores and even large box stores.
Answers to frequently asked storage questions
What's the best way to store thread?
Storage drawers are ideal for protecting thread from UV rays, which cause deterioration and dust. One expert told me exposure to air conditioning, and heat dries the thread and diminishes its quality. All sewing machine threads have lubrication that evaporates over time, especially if exposed to air conditioning and heat. As a result, the dried-out polyester thread will flake.
Open thread racks should only be used for thread spools in current use. If you don't have a closed storage space, make a cover to protect your thread.
How long will thread last?
It all depends on the initial quality of the thread and the way it's stored. A thread that is kept clean and away from UV rays lasts much longer than a thread that is not.
Does freezing thread revive it?
Forget the advice to wet, refrigerate, or freeze thread to rehydrate it. These so-called remedies cause more problems. If the thread is not performing as it should, discard it.
Quick Guide to Choosing the Correct Thread
This is just a quick guide based on fiber makeup, and common industry uses.
Cotton thread is great for sewing other plant-based fabrics, like linen, cotton, and rayon.
- Soft, warm, absorbent, dyes well
- Shrinks with high heat, no 'give", deteriorates over time.
- Extra-long staple sews best
Bonded nylon is great for utility-type projects, like tool belts, camping equipment, and sports gear. Pay special attention to how nylon is finished to determine its properties.
- Properties vary depending on the "finish."
- Highly elastic with good recovery, won't shrink, and strong.
- Not color-fast will melt under low heat if not "bonded."
A polyester thread is synthetic-based and is entirely man-made. It’s low maintenance, durable, long-lasting, and relatively inexpensive. These qualities make it perfect for All Purpose Thread.
- Long-lasting, strong, and inexpensive.
- Withstands moderate heat, won't shrink, minimal "give."
- Not as soft as cotton or silk and is less absorbent than cotton.
Many people use rayon for their embroidering, topstitching, and monogramming. We don’t recommend Rayon thread for seam construction because it’s not as strong as polyester and becomes even weaker when wet.
- High shine, dyes beautifully, fade-resistant, and highly absorbent.
- Weak, not ideal for seams.
- Best used for decorative stitching and embroidery.
Silk is often used in fine tailoring, fine embroidery, sewing on buttons, and when finishing the edges of buttonholes.
- Fine, flexible, strong, good elasticity, lint-free.
- Dyes well, colorfast.
- Great for hand-sewing and fine tailoring, expensive.
This animal-based thread is created from sheep's fleece and can be spun into fine, medium, and thick weights. Wool thread is commonly used during hand needlework, but specially designed, fine wool threads can be used in machines. It’s especially useful when embroidering thicker fabric and when you want your design to have great texture. It also dyes well, creating deep, rich tones. Wool thread is soft, durable, and warm and works wonderfully in constructing wool clothing and blankets.
- Soft, durable, warm.
- Wicks away moisture.
- Beautiful texture, dyes well, good elasticity, will shrink, and loses strength when wet.