The Black Fabric Fiasco

So, I've been working on this project, piecing letters and star blocks, and using solid black fabric as the background for all of them. I had some black fabric in my regular stash, but when I used that up, I went hunting, and found a big piece - about 3 yards - in a cardboard box. I had an UFO (unfinished object, a common term for us quilters!) in the box, including many pieced blocks, and the large piece of solid black. Do you see where this post is going? I cut off a large piece of the black, about 1/2 yard, and started to press it. Black dust and lint were everywhere! On the ironing board, on the floor, and on me. I decided to wash that piece, and the remaining 2+ yards - so into the washing machine they went!
And this is what came out! I was upstairs when Scott removed them from the washer, and I could hear him exclaim when he saw it! He was shocked, to say the least! What could I say? We had a good laugh over it, and now I have to decide how to proceed.

Last night, I hand washed all of my completed blocks and letters, and I think I can salvage all but about 4 of the letters. I could definitely tell which ones had the "bad" black fabric - it left a ring in the sink! Apparently, the acids in cardboard boxes leach into the fabric, and cause it to break down. I had just never seen proof of it until now!