We saw this and had to try it IMMEDIATELY. Fortunately mom hoards milk containers and other recyclables like Kane hoards toys and we were able to freeze some ice blocks overnight. Given the increasing likelihood that Kane and I will turn art/craft time into Monday Night Raw and my diminishing afternoon nap (if mom would just let me give up my morning nap, I swear I'd sleep for more than 45 minutes in the afternoon), Kane and I have been able to each have some time alone with mom in the afternoons to do arts/crafts. I was up first with the ice painting -- I spent a long time carefully spreading salt over the top of the ice block and then licking my fingers each time before going back to the salt bowl. I eventually worked my fingers cold and picked up the mini squeeze bottles in which mom had mixed up some liquid watercolors. I didn't spend quite so much time painting, but that is largely due to the fact that by that point I had ingested so much salt that my baby reflux kicked back in and I threw up all over myself (fortunately mom remembered the tell-tale signs and moved my art work out of the way first). No worries, I went right back to eating my rainbow goldfish (which do come back up rainbow, incidentally) and painted a bit longer.
Kane took a slightly different approach -- he wanted to put salt all over his ice block -- not just on top. He spent a really long time (for him) doing that and then wanted ALL of the watercolors (big surprise). He also asked for a spoon after a while to spoon the watercolors pooling in the bottom of the pan back over the top. All in all, it was the first art/craft project in a while that occupied him for a serious amount of time. And even as we kept playing throughout the afternoon, we took breaks to check out what our ice blocks were doing. So, needless to say, we were all fans.
Next time we might try it with food coloring and/or colored sugar -- it kind of looks like a super yummy snowcone. And we all know I'll eat it anyways.