mckwilter

For me, the cover on a HWB isn't to keep the content hot, but to keep the hot contents from burning my skin. Whatever you use, the contents of the HWB will cool. I used regular cotton batting with a polar fleece cover, nice and cuddly, for mine.

I make rice bags, too, but for around the neck I use cotton socks. For larger ones, I use terrycloth wash cloths and dishtowels. I sew tubes, then divide the rice into equal amounts. Pour some in, then sew that section shut; pour and sew, wash, rinse, repeat. I made one for my back using two dishtowels, so first sewed channels then filled and sewed across to make small rectangular sections. Using this method, the rice bag stays flat instead of it all shifting to one end.