Silica gel's high surface area (around 800 m2/g) allows it to adsorb water readily, making it useful as a desiccant (drying agent). Once saturated with water, the gel can be regenerated by heating it to 120 °C (250 °F) for two hours. Some types of silica gel will "pop" when exposed to enough water. This is caused by breakage of the silica spheres when contacting the water........(From Wiki)
Reactivating the Silica Gel in Microwave. Recommend doing this to the fresh sample also before adding to the camera bag so that absolutely fresh and hungry for moisture silica gel is added to the bag for camera protection. Take about 15 mins over all. In my camera bag, I keep 10 packs of 10 gms each around the body, lenses, flash.
July 2014 Update. Now I weigh the One ounce packs, with wrapper these are at 33 gms. After 1 min at high and followed by 5 mins at Medium, the weight is 25 to 26 gms. A tea spoon of water expelled. As soon as the silica is cooled to room temp, I place these in the bag. I live in tropics, Mumbai, 30*C and 75 to 85% RH. I do this once 20 days. I use 2 one ounce packs for the air tight boxes for body, and for prime + the long 70-200 mm. 4 boxes, 8 packets of one ounce each.
Video is made with a cell phone camera.