Hello, I'm trying to create the coldest freezer pack that is still soft and pliable. (Or will at least soften up within 10 minutes). It should also ideally stay cold for as long as possible. I've experimented with a few options so far and Water + Glycerin seems pretty good. If you add just a small percentage of glycerin, it's actually like a packed snow consistency. It can feel hard if you press on it softly, but when you apply more pressure, it crumbles easily. What i want to improve on is it's ability to freeze even colder (ideally -30C which is my chest freezer temp) and stay cold for longer. Water seems to hold cold temperatures longer than most other liquids I've tested (i think it's called the heat of fusion right?), but then I tested this one coldpack from Walgreens called Cryomax. This seems to stay cold even longer than water (problem though is it's actually hard out of the freezer). Here's the cryomax: http://www.modularthermaltech.com/products/index.html. So is there anything i can add to the water + glycerin concoction to make it freeze colder, stay cold longer, but still be soft and pliable right out of the freezer?. I've heard salt and starch might help and wrapping the pack in neoprene will too. This cold pack is going to be integrated into a protective sports cooling vest design so that its why it needs to be somewhat soft and cushy. Also, it needs to be non toxic. Any ideas?