This product is great overall. First use out of packaging is fine, but I did have a problem reusing it, until I read the other review on this page. In my opinion, the easiest way to reuse this product is to boil some water, and put it in a pan still boiling. It takes only a few minutes for all the crystals to dissolve, MUCH easier than boiling with a cup of water. Heat generation is adequate. Again, a very good product and serves its purpose well.