With the electricity out last week I had plenty of time to straighten and clean the studio. So with a lot of old thread on hand I gave each spool the strength test: take an 8″ length of thread, tie a knot in the middle, give a gentle tug and if it breaks it is not strong enough for sewing. They all failed.
These empty spools will be repurposed in ArtBreak this fall at school, or maybe used to hold lengths of ribbon and string. The old wooden ones are nice objects, especially the orange Belding Corticelli.