While we're waiting for the lemon battery do-over (and possibly other redox experiments), I thought I'd take another look at what the alum crystals are doing.
John had to stop growing the clear crystal when the string broke before Christmas. Anthony is still growing his green crystal, but it's getting ... kind of mushy. I think it has to do with the new solution we put it in.
We tried to make more "alum juice" by taking all the grains of alum we saved after siphoning off the liquid from time to time. Anthony warmed the juice in the microwave so that the alum would dissolve, but I think he let it get too hot. We left the cup of juice to cool to room temperature and went out for the day. (If we had put the big crystal back in the juice when it was still warm, it would have dissolved, because the warmer liquid could take more alum into solution.)
When we got back we found the big chunks of alum you see here. They're sort of deformed, I believe because they formed too fast for the crystal structure to develop nicely. It's interesting that they kept the green food coloring as well, which the slower growing crystals didn't (once they had dried). We may dissolve them and try again.