Your choice of thread depends on your choice of fabric. That said, you want a good quality thread. Thread that is more than a decade old should be put aside for making muslins because thread does degrade in quality over time.
Fabric Choice and Colour are the two main criteria when selecting thread for your garment. I tend to use a general all purpose polyester thread for most projects because I like the strength and durability that it provides. Cotton thread is weaker and on kids clothes, this can be a problem, so over time, I've realized that polyester thread is always a consideration. Thread used for construction needs to be stronger than decorative thread.
Colour Choices: the rule is to choose a darker shade (one shade darker) thread colour from the garment fabric and it is one I use. But on lighter fabrics, a shade lighter tends to disappear more easily.
Different Thread Choices:
General Purpose: these can be mercerized cotton or cotton polyester or polyester. These are suitable for using in the sewing machine and are also sold in cones and are ideal for serger sewing too.
General Purpose Polyester Thread: It looks, feels, and performs like nylon thread. But, there is one important difference - polyester thread has superior resistance to sunlight (UV), mildew, and abrasion. It is resistant to aging - see below on the shelf life of thread. This makes polyester thread the first choice for sewing, binding or wrapping anything that is consistently used outdoors or in moist areas.
Nylon thread is a good choice for heavy, sturdier fabrics. Use nylon thread for sewing almost anything that requires strength and durability. It is strong, easy to use, and a great choice for sewing fabric, leather, canvas, and vinyl.
Cotton Thread: The fibres are short and if not made well, or if it is an aging thread, will produce a lot of lint. So you must invest in a good quality cotton thread, should you choose to use one. Also, be sure to clean the sewing machine after sewing a garment with cotton thread. Mercerized cotton is less prone to lint that non-mercerized cotton thread.
Rayon thread: this is made of a combination of natural and synthetic fibres. It comes in a variety of colours that make it ideal for embroidery. But rayon thread is not strong enough for garment sewing. It may also not be colourfast - a real issue for all sewing projects.
Silk thread: ideal for sewing silks and wools. Stronger polyester thread can tear the fabric when a garment is worn - so when sewing silk or wool be sure to look for thread that matches the fabric choice. This thread is soft and gentle and tends not to knot easily. It is a lot pricier than polyester though.
Machine Embroidery Floss: This is made from polyester and rayon fibres and has a high sheen. It is this high sheen that reflects the light and makes this idea for embroidery. This thread is thick, so be sure to match needle size and to only use as a top thread (use a plain cotton or polyester black or white thread in the bobbin.)
Heavy Duty/Upholstery : This thread is intended for sewing upholstery and other heavy or stiff fabrics. It is usually made from nylon. It's just about the strongest of all the threads available on a spool. It's also thicker than most other threads.
Metallic thread: I bought metallic thread recently because I want to use it for top-stitching a pair of jeans. It is a heavier thread and requires a specific needle to keep the thread from breaking.
Mono-filament/Transparent Nylon - Colorless and very strong, this thread is a good choice when you need invisibility.
Bobbin Fill: This is a fine thread usually available in bobbins that is used to reduce the bulk on embroidered designs.
Basting thread: This soft, cotton thread is not as strong as the all-purpose thread and is used for basting stitches. It will not damage fabric when removed.
Top-stitching thread: This thread is designed to stand out. Look for it in bright colours as well as black and white. It is stronger and thicker and should be used with a top-stitching needle. (And with general purpose thread in bobbin - to save money and reduce bulk!)
There is no universal scale for thread weights. Generally, the higher the number the lighter the thread weight.
And choosing thread for your project doesn't have to be difficult: think of the wt of your fabric and find a suitable thread for it: denim requires a sturdier thread whereas a sheer fabric requires something light-weight.
For the math-minded: Dividing the length of thread by a set weight derives the exact measurement of a thread weight. A thread is labeled 40 wt. because one gram is 40 meters long.Whereas a thread labelled 20 wt. is much thicker because a much shorter thread weighs the same as a 40 wt. (this is the fixed wt system)
Length — in length measurements, higher numbers reflect thicker or heavier threads. "Denier" refers to the weight in grams of 9000 meters of thread. If 9000 meters weighs 1120 grams, it is a 120 d thread. Most embroidery threads are 120/2, which equals 2 strands of 120-denier thread for a 240 denier total. (this is the fixed length system)
"Tex" refers to the weight in grams of 1000 meters of thread. If 1000 meters weighs 25 grams, it is Tex 25.
The physical size of thread affects your project:
- Both top and
bobbin tensions —
Changing the thread physically changes
the tension. When thread size is
changed, the upper and lower tensions
should be checked.
displacement — Too many thread fibers in a set
space make the fabric pucker - Iincrease
- Needle selection — Eye of the needle should be 40% larger than the diameter of the thread. When going to a larger size thread, a larger needle should be used.
More About Thread:
Test the Quality of Your Thread:
- look for a smooth,nub-free strand that doesn’t twist easily and is as free as possible of fuzz
- Do this by holding the thread up to the light for visual inspection and by rubbing it with your fingers.
This goes without saying really, but I will say it: run a test swatch for tension, stitch length, etc.
Also, I note what thread, tension and stitch length on a sticky note and post it on my pattern envelope. That way, if I put a project down, I can return to it and be sure of that I can take it up immediately.
Test for the Shelf Life of Thread: Thread does have a shelf life and if it is exposed to air or light for too long, it can get brittle. There really is no official way to tell if your thread is past its shelf life so one way to test your thread is to take a piece about 8" long, tie it into a knot in the middle and then give it a gentle tug on both ends. If the thread breaks, it is time to get a new spool. (old polyester thread flakes...)
What causes thread to get old?
- Exposure to heat and air conditioning (your thread should be stored in a drawer or at least, have a covering)
- UV rays
Is Your thread too old? Don't toss it: save it for use when making muslins.