Techni Ice reusable ice packs. Techni Ice HDR consists of a 4 layer construction. Techni Ice has two outer layers are of heavy duty plastic while the two inner plies are made to resist puncture and holds the main ingredient to Techni Ice, a refrigerant polymer. Techni Ice is made of a puncture resistant material is actually a cross-linked polyacrylate polyalcohol co-polymer refrigerant that’s combined with a proprietary secret formula. Even if the plastic rips, the inside layer will hold the Ice in. Hydrating: When new, the Techni Ice comes in extremely thin sheets that require hydrating before freezing or heating. To activate the cells, simply fill a bucket or sink with warm water; cold water will work as well, but warm works best from what we’ve experienced. Immerse the sheet in the warm water for about 90 seconds while scrunching the Techni Ice. You will know when they are done and the Techni Ice recommends that you leave a thumb indentation in each cell during the swelling to allow room for expansion during freezing. When we hydrated 10 sheets, we found that having all cells submerged during the procedure is important, and even so, when crunching the cells, not all of them will expand at the same rate which required more work to get them to the desired size.