After much experimentation I've done it. I made a salt shaker! It's my entry for the edible book festival that 826 Seattle is putting on. I'm doing Salt: A World History.
It was actually much harder to do this than I thought it would be. I thought I could just wet some salt a little bit, shove it in the mold (Rakka already published pictures of the mold making), and it would dry solid. Wrong. It stayed mushy.
So I tried some white glue. Yeah, not very edible, but kids eat paste. Anyway, it didn't work. The salt solidified it in to little balls, instantly. Weird. So I tried gelatin, at Rakka's suggestion, but it prevented the gelatin from setting. Ugh, that one was gross to clean up.
Time to drop a little bit of Science. Salt does weird things to water. I'm not a chemist, so I don't know all the details. But I'm pretty sure that's why the glue and the gelatin failed so horribly. What I needed was a binder with no actual water in it. My next attempt was with corn syrup.
Corn syrup is in everything these days anyway, why not salt sculptures? You can get it at any old grocery store; Karo is the brand we get around here. It's pretty viscous at room temperature, but I didn't want to cook the sugar. So I heated it in a double boiler setup.
This worked well. The salt didn't do anything weird with the sugar at all. It just got sticky. It got very grainy, almost fluffy.
But it compressed well. I just shoved it in the mold as hard as I could. Then tied up the mold so it didn't move around. A couple hours in the freezer and it was as hard as a rock, though a bit skewed. I squared it up a little bit with a small cheese grater.
The best part is the salt crystals are still visible. It's exactly what I was looking for.