The truth of the matter is that thread selection can play a major role in the making of a quality product. Threads differ in many ways including fiber content, method of manufacture, finish, size and strength. Using the wrong thread in the wrong fashion can cause shortened life, puckering and rippling.
Types of Threads
When choosing a thread it is important to consider the different types available. What fiber content will you want? Will the method of manufacture affect your finished product? Does it matter what finish the thread has? What size thread will you need?
In terms of fiber content, there are three main types: cotton, nylon and polyester. Cotton traditionally has been the most widely used thread, though Klein points out, "The use of cotton thread in the industry is declining. It's not as durable as polyester and more prone to shrinkage." And because prolonged exposure to sunlight weakens them, nylon fiber threads should not be used in window treatments. Therefore, polyester threads are becoming the most accepted for use in the industry.
Another distinction between threads occurs in how the thread is manufactured. Here, there also are three main types: spun, filament and core spun. Spun is the most economical and versatile. It can be used in a wide variety of machines and is less likely than filament thread to cause puckering. Yet it is not as strong as filament thread.
With filament thread you can use a finer thread and produce a stronger seam. Filament thread also yields the cleanest seams. But those seams are apt to pucker, and filament thread costs more than spun thread. Core spun is a combination of filament and spun thread. It is strong, produces clean seams and does not tend to pucker. The downside, though, is that it costs more than either one.
Most sewing threads are treated with a finish further complicating our search for the proper thread. Thread finishes can include mercerized, glace and bonded in addition to various fire retardant and heat resistant resins that also are applied to threads. Do not confuse fire retardant threads with heat resistant threads. Fire retardant threads produce inflammable fabrics. Heat resistant threads are for use in high-speed sewing.
Of course, the cheapest thread will be an unfinished, soft thread. This type will be the easiest to sew with but also the weakest, so you won't be able to find a very fine unfinished thread. The most common finish is mercerized cotton. This finish strengthens and solidifies the thread making it more lustrous and capable of producing a better seam.
The glace finish produces an even more polished cotton thread that is used in the manufacturer of shoes and luggage. It offers limited application to our industry, and as Klein says, polyester threads are displacing cotton threads.
The majority of polyester threads are bonded. That means they have been treated with a resin or wax to create a protective coating. This coating increases strength and produces a thread that is much easier to use. You can attain a much finer polyester bonded thread with the same strength as a much thicker cotton thread.
By the Numbers
Threads also vary in terms of their size and sizing methods. Usually the size appears as a ticket number. Three different sizing methods are used to acquire that ticket number depending on whether you have filament, mercerized cotton or unmercerized spun thread.
Filament threads use the denier designation with the last digit dropped. Mercerized cotton threads have a letter system rather than a numerical one. Sizes range from the coarsest size "F" to the finest size "OOOOO."
The ticket number for unmercerized spun thread corresponds to the yard count of the thread. Therefore a thread that is a 40/3 yarn will be 40 thread. Adding to all this confusion is the fact that threads finer than 40 have heavier ticket numbers than what the actual yarn count is -- for example, a 50 is actually a 45; a 60 actually a 50.
The Tex system has helped clear some of the confusion. It strives to place a uniform standard for all threads by offering numbers that correspond to the thickness of the yarn. The thicker the yarn is, the higher the Tex number will be. This system has not been widely accepted, and the other measuring methods continue to persist.
Choosing a Thread
So with all of these different criteria for sizes, types and finishes, how are we to know which thread to use for which application? Trying to choose from all these variables would drive us all crazy, wouldn't it? It would except for the most part, as Klein points out, workrooms traditionally choose one thread then stick with it.
Staying with the thread you've been using might have to do with what machine you use. "Workrooms will go to the equipment salesman and ask for a machine for a specific purpose," Klein says. "He will make his suggestion based on a specific task without considering other thread sizes. Therefore you'll end up with one machine that can't handle smaller threads."
What guidelines should we use to avoid this scenario? How can we escape relying too much on one thread or on a limited machine? When choosing a thread we should consider the thread size, strength, and the type of fabric we'll be working with.
In general, ticket number 23 is the most commonly used size of thread in the industry, according to Klein. But a workroom should not simply use 23 thread without first considering some general rules. For example, the thread should be as fine as possible, yet in line with the strength requirements of the seam. Finer threads allow for finer needles and therefore will create less fabric distortion than thicker threads. So choosing a finished thread rather than an unfinished one, or polyester rather than cotton, will result in more uniform seams.
It also is important to have a strong thread, but not too strong. The tensile strength of the seam should be around 60 percent of the fabric strength so if a tear occurs it will occur at the seam rather than straight through the fabric. An example would be blackout lining. Klein recommends a three-and-a-half pound test strength thread for sewing blackout lining. But using that same thread on a lighter fabric could result in seriously damaging the draperies. And we all know that repairing seams is much easier than repairing ripped fabric.
We also should consider the cleaning requirements of the fabric when choosing a thread. Does it require washing in hot water? Or does it demand dry cleaning? If so, expect a color change in the thread if you use cotton. Even worse, look for shrinkage and puckering if you use a cotton thread on a synthetic fabric.
The different finishes offer less of a dilemma, except for the fire retardant resins. Applying the resins to woven filament yarn fabrics results in puckering and rippling. This is truer for lighter weight fabrics than heavier ones. The puckering can be minimized by using a finer, yet stronger thread such as polyester and sewing at the lightest tension possible.
It also is important to sew evenly. The bottom and top fabric should feed into the machine at the same rate. Sewing in this fashion with the correct thread can lessen future fabric distortion.
As for the machine, it is important to have one that can handle finer threads. In order to deal with fire retardant fabric in the manner discussed above you must have a machine that can manage fine, strong threads. A lot of machines cannot. Klein deals with many workrooms that refuse to invest in the proper machinery. As a result these workrooms end up with products that pucker and ripple because they could not use the correct thread.
The machine you have determines the thread you can use. Keep that in mind when purchasing a new machine. If you intend to work with fire retardant or other resin-coated fabrics, it is essential you have a machine capable of handling the finest and strongest threads.
So, to avoid coming undone at the seams give more thought to the thread you use. Rather than going along with what seems right, pay attention to the thread's content, origin, finish and size. Remember the guidelines offered here. You'll achieve a higher quality product, and you'll never take thread for granted again.
Cheryl Strickland is owner of Professional Drapery Seminars. She is an internationally-acclaimed speaker with more than 20 years experience in the window coverings industry. She is the publisher and editor of Sew WHAT?, an international monthly newsletter for professional drapery workrooms. Strickland also is the author of A Practical Guide to Soft Window Coverings and the Designer's Sketch Pad, which are available through Draperies & Window Coverings magazine.