WTT!! (What The Thread!) Part 3

As promised here is the third and final installment of thread education!  Here I’ll talk about what thread terms mean.. some you may hear when reading or discussing thread, how thread is sized and and explaining the ‘finishes’ on a thread.

In case you missed it:

WTT!! Part 1
WTT!! Part 2

Sew let’s get started!

Thread Terms

I’ll start with what I ‘think’ you may have heard most often and move into less frequent terms.

Spun: This is when staple fibers are twisted into single strands.

Plying (or Ply): This is the process of taking 2 or more spun strands and twisting them together to form thread (or yarn as the case may be).

Textured Thread: This is just a process of crimping filaments to create different textures (bulky, softness, elasticity).

Core: This is as it suggests.  It’s the central fiber (polyester, nylon, cotton) in which a staple fiber is wound around.  The staple fiber or outer fiber could be the decorative metallic, could be polyester, etc.

Staple fibers: Natural fibers that are very short in size (think of the size of a cotton ball) – up to 2 inches.  Synthetic fibers that are double or more in size – up to 5 inches.

Monofilament, Multifilament, Triobal Filament: Monofilament are single extreme lengths of fiber (polyester, rayon, nylon, silk).  Multifilament is just as it suggests – several strands of extreme lengths of fiber together.  Triobal is a filament that has three sides for light reflection.

Thread Size

You may have noticed – especially if you’re into embroidery – there are different sizes of thread.  As you can imagine they are linked to the weight of the fabric you’re sewing into.  Light delicate fabric should have a light delicate thread (remember you want to match your thread to your fabric in most cases) and heavy weight fabrics such as jeans should have a thicker thread.

In my experience and research there doesn’t seem to be an industry standard.  But what I did find was some generalities. Thread2 Additionally, I had come upon a website selling thread that bespoke of Tex sizes.  What?

Here’s what I’ve found:

Weight: how many kilometers a thread has to be to weigh in at 1 Kilogram. The higher the number the lighter the thread.

Tex: the weight in grams of 1,000 meters. The higher the number the heavier and thicker the thread.

So here is a nifty generalized chart that should help you if size matters to you:

Fabric Type

Thread Weight

Tex Weight

Suggested Needle Size

Extra Light 120-180 16-24 60, 65
Light 75-120 24-30 70, 75
Medium 40-75 30-40 80-100
Medium Heavy 30-50 40-60 100, 110
Heavy 25-36 60-105 120, 140
Extra Heavy 11-20 105-135 140, 160

Please keep in mind this is a very generalized chart as there is no industry standard!  I have compiled this from reading many websites and books on thread.

Most important, just remember, in metric sizes, the higher the number the finer the thread.  In TEX standards, the higher the number the thicker the thread.

Now for our final section….


Finishes refers to the final touches on the thread before it is wound onto the spool.  It’s kind of like a helping hand for the proper type of lubrication.  For instance, serger thread is treated to enhance high-speed sewing – otherwise it would break constantly.

Bonded: This is a coating to keep polyester and nylon abrasion free and shred resistant.

Mercerized: This process adds flexibility to cotton or cotton covered polyester thread.  It reduces lint (important for your sewing machine!!), gives it strength and shimmer as well as making it useful for the dye process.

Glazed: This is actually only useful for hand sewing.  Any glazed thread will not bode well in your machine!  This process uses any number of chemicals and waxes to give thread a glossy smooth surface that reduces the amount of tangles and knots.

Gassed:  Simply a flash fire on thread to remove lint and give it a smooth look.

Soft: Untreated cotton.  In other words, nothing has been done to this thread so use it with caution because as we learned in Part 1, cotton is the weakest in the thread family.

And there you have it….all that I know about thread.  I do hope this has helped you in your learning process and adds a bit more to your arsenal of knowledge.

Let me know what you’d like to know more about!  I’m happy to share everything I know.  Don’t forget to check out the most recent tutorial on a Continuous Thread Dart.