Does Sewing Thread Go Bad? How to Know When to Use It or Toss It

Have you ever received a box of old sewing notions from a neighbor, friend, or family member?

I know I have! It's hard for me to turn down free fabric and notions when someone is getting rid of them. Grandma's sewing machine and her good shears are probably fine for another generation or two. But the thread? That's a different story.

So does sewing thread go bad? The short answer is: yes, it can. Here's how to tell the difference between thread that's still usable and thread that's going to cause you problems.

What Affects Thread Longevity?

Thread is a textile, and like any textile, how it's stored makes a huge difference in how long it lasts.

Thread kept in a cool, dark drawer or box will be in much better shape than thread left out on an open rack near a sunny window. Light, heat, humidity, and dirt all degrade thread over time. Natural fiber threads like cotton are especially vulnerable to dry rot, mildew, and even insect damage if stored in less-than-ideal conditions. Older polyester threads from discount stores can also be problematic because they weren't spun as well as modern core-spun or microfiber polyesters, and they tend to shed excess lint.

As a general rule, long-staple polyester threads and cotton-wrapped polyester core threads hold up better over time than 100% cotton thread.

How to Test Old Thread

You don't need a lab to figure out if old thread is still good. Here's a simple test:

1. Pull off a length of thread and hold it taut between both hands.

2. Slowly pull your hands apart (don't jerk it) and see what happens.

If the thread stretches and the fibers start to separate before it breaks, that's a bad sign. Set it aside. If you get a clean, sharp snap or can't break it at all, the thread is likely still strong enough to use.

Should You Use It or Toss It?

Even if your thread passes the snap test, think carefully about where you're going to use it. Old thread is not worth risking on a sewing project where you've invested time and good fabric.

Here are some smart ways to use up old thread rather than throwing it out:

• Hand basting (temporary stitches that get removed anyway)

• Decorative stitching where strength isn't critical

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According to textile expert Bob Purcell, the high-quality threads made today should last for generations. But the same can't be said for threads manufactured decades ago. Relatively recent "old" thread may still be perfectly usable, especially if it was stored well. Just be cautious about using it on anything important.

When it comes to thread, cutting corners isn't worth it. Thread is one of the most fundamental components of a sewing project, and weak thread means weak seams.

Related reading: How to Store PDF Sewing Patterns