Thanks for the heads up--will check my UFOs.

It is the humidity that caused the rust. I had the same thing happen when I stored a counted cross stitch needle on a aida cloth scrap.

Whink rust remover will remove rust on colorfast fabrics.

I use coated bobby pins (the kind that used to make pin curls in hair years ago (LOL) to hold the fabric in place after I ruler fold it. Have not had an issue with rust even though I live in Florida with our high humidity.

When I volunteered at the thrift shop, we had bunches of fabric come in with this problem. I guess that was one of the reasons it was donated. I bought a lot of this and cut it into squares for quilt tops. I had to fussy cut around the rust spots. It caused some troubles, but it was cheap enough to put up with the headaches.

Wow thanks. Will give that a try

For that amount of 'pins' several people could go together and get them and share the cost; minimal expense.

Another cheaper option; use your cut off selvages to wrap around the fabrics if on a board.

Leaving a threaded needle in fabric for a long time will also cause rust.

When I was collecting vintage fabrics to sell, I used brass safety pins to hold on archival (non-acid) light cardboard tags. Never a problem despite living here in the humid Seattle area and storing some of those fabrics for decades.

I often find old fabric at thrift stores and estate sales with this sort of problem, staples do it too.

On a side but related note, for those of us who store our fabric in cardboard boxes, never have those boxes directly on concrete floors, they will wick up small (or large!!) amounts of moisture and give you that musty smell.

My LQS uses those snap clips you use in hair.