Talk:Cooling vest

If you google a search of "phase change cooling vest" you will find cooling vests and other apparel which use RPCM (Renewable Phase Change Material). The nearly clear oil-like substance hardens into a waxy white substance. When applied to the skin via a cool pack, it cools at a consistent 58 degrees Farenheit (15 C). Thus, it cools the skin without freezing and typically lasts from 1 to 2 hours. Because of the low "freezing" temperature cools packs can be hardened in 20 to 30 minutes in ice water, or 60 to 90 minutes in a freezer, or 2 to 3 hours in the refridgerator.

None of the clothing suited for the cool packs needs to be wet. Thus, the cool packs work at 58 degrees F (15 C) until they are almost completely depleted in most any temperature extremes regardless of humidity. Evaporative cooling devices need to be wet and only cool up to 12 degrees below ambient temperature. Plus they do not work well in high humidity or little air circulation.

Like any other frozen substance, melting begins because of temperature differential. Obviously, extreme heat and direct skin contact deplete them quicker. However, I have two 6" square RPCM packs which I have let sit out between 18 to 24 hours in a 70 degree Farenheit room. (They were touching and stacked.) Even after that period of time the cool packs remain between one-half and one-third charged. Amazing.

Therefore, even if your ice water is depleted, it simply needs to stay cooler than 60 degrees to keep the phase change material from melting. I suggest having the cool packs frozen before you ice them for the first time because they really suck the cold out and melt ice quickly.

The Phase Change material is supposedly developed by Nasa and is made primarily from fats and oils. Thus the FDA declare them "food safe" though consumption is not suggested. If broken, the phase change oil may simply be washed away with soap and water. —Preceding unsigned comment added by 151.198.154.17 (talk) 19:56, 28 October 2009 (UTC)