Can only use it to the wool yarn.
Hi Deborah: Here is a really interesting site and may be what you are looking for. At least give it a read:) It's more to your interest near the middle/end.
Here's a tutorial for how to make the solution: http://dayindayout10.blogspot.com/2012/03/mineral-dye-copper-penny-blue.html
Your're welcome! Good luck!