I was sewing the other day and finished up the 1200 yd spool of gray thread that I would swear I just bought. I switched to beige and finished off that spool and fortunately had another one in reserve. We tend to just sew and sew and not think about the thread we're using, but it is important. Without the thread nothing would hold together. With the wrong thread, something could be ruined. With the perfect decorative thread, you can create art. When the thread runs out your day could be ruined. Old thread is weak and can break and new thread is so expensive that it is an investment.
I took a class in using decorative threads and learned a valuable lesson which is to "match the thread to the fabric". Cotton thread is weaker than poly/cotton, which is weaker than polyester, which is weaker than nylon. If you sew with a thread weaker than the fabric, the thread can break (hence the classic ripped crotch problem). If the thread is stronger, the fabric will rip before the thread breaks and you have a hole you probably can't fix. If the thread and fabric match, everything will wear evenly. I have a perfect example of the wrong match of thread and fabric. One of my purchased comforters is quilted with nylon thread which is not only strong, but sharp. The fabric is tearing and separating all around the quilting and there is nothing I can do. Another purchased comforter is a poly/cotton blend and must have been quilted with cotton because the stitching has popped all over the quilt.
And since I mentioned nylon thread-I do not recommend it for any quilt that will be actually used by humans! Fine and dandy for wall hangings but just not good for lap or bed quilts and especially not for baby quilts. The reason is that the thread is very strong and feels sharp where it is cut. Also if you miss a loop somewhere it is very dangerous to a little toe or finger that might get caught in it-very scary! Unfortunately I learned this the hard way. My favorite thread for machine quilting is a very fine basting thread, which I am having trouble finding any more. It is just the right strength but fine enough not to be too visible. Every now and then I do a search, but haven't replenished my supply.
I really love the variegated threads for machine quilting--expensive but beautiful. I am so glad that they are now available in big spools and I am very thankful for those regular JoAnn Fabrics coupons!
So, check out your threads and make good choices because we want all of our hard work to outlast us!