I made these years ago with crimped corn. When you use crimped corn it doesn't pop. Pop corn is actually a specific type of corn variety. That's why we have so few old maids in the bag. (I think long ago regular corn was used) Anyway, I don't think sand would heat up as nicely. Recently the quilters around here are using Walnut shells in their pincushions. It is ground down to a smaller pebbly size, and it sharpens the needles. You get it at the chain pet stores, I think it is bedding material. I think you could use this material. It wouldn't get pantry moths, I think it would heat up, and wouldn't be as heavy as sand. My neck warmer didn't have anywhere near that amount of rice/corn in it.