You were all on the right track. Here's the deal. It's copper tubing in a solution that's 1 part ammonia, 2 parts water. The ammonia reacts with the copper to create the blue color, and the copper acts as both the mordant and the coloring agent for the wool. The wool is supposed to end up some shade of mint or seafoam green, like copper patina. The rolags in the photo are kind of sage green and came from Martha's copper jar in our class. My wool ended up a light beige with a slight greenish cast. There was a warning on the instructions that the first attempt with a new jar and new copper might give me a brown instead of green. Yup! So now the solution is a cloudy green, and I will wait a while before trying it again. I might try to overdye this skein, shown next to original undyed for comparison), or I might learn it's not good for the wool and I'll just use this as is.
In other dyeing fun, I mordanted a few skeins yesterday in preparation for later dyeing.
I used alum and cream of tartar - yummm, the fragrance of cooking wool!
The resulting skeins, drying and waiting for dye at a later time.