I am cleaning up my sewing stuff and found a box of threads, at least 50 spools of Guttermann. Some of it might be 15 years old!! Should I just throw it out, or save it to use? Also, how do you tell if it is cotton or polyester on a bobbin? I used to use poly for clothing sewing, but now all my time is spent on quilting with cotton. I think that my time is worth more than an old spool of thread if it damages my handwork. What do you all think?

Break thread from a new spool and then break thread from the older spools. If it has the same strength it's good thread. You can tell ploy from cotton by burning a little. Cotton will turn to dry ash, poly will leave a sticky globby ash.

If the thread is dry and brittle (the breaking test should determine this), you can revitalize it by placing it in a plastic bag in the freezer for a couple of months. This restores moisture to the dried-out old thread. Test it again afterwards, of course, to make sure it has become as strong as new thread.

I think the burn test is the only way to determine if thread is cotton or polyester. If you hold a match to the thread, poly should melt into a blob while cotton should turn into ash.

you can revitalize it by placing it in a plastic bag in the freezer for a couple of months. This restores moisture to the dried-out old thread.

Wow! I've been sewing and quilting forever, and I did not know you could restore moisture to old thread. Thank you so much for this info.

I found some that was bought at a store that went out of business over ten years ago. I wrapped some around my hand and gave a really good firm pull from the spool. Since it did not break, I used it. It was just fine.

Wow..I didn't know about the Revitalizing of old thread either, thanks so much Prism99 for that Great Tip, I still say we need a{ Tip } section here on the board so everyone can see and find it easy so all can benefit from them.

This is new info to me. Thanks.

I thought keeping things in the freezer would dry it out? I was told not store certain things in the freezer as it would draw out the moisture.

just test it by pulling on it.

I've heard this before. Have you tried it?