are all silica gel packets reuseable? and, if they aren’t specifically labelled ‘color indicating’, how can you tell when they’re saturated? Also, do you leave them in their packets for recharging in an oven or microwave, or do you take the beads out of the packets? In advance, many thanks.
In: Chemistry
Silica gel works by absorbing (or is it adsorbing? I can’t remember) water. To drive that water off and “regenerate” them, simply heat them up over 120˚C.
Silica gel can absorb up to 37% of its own mass in moisture in very humid environments. In areas with lower humidity or higher temperatures, it will be less, as there’s sort of a dynamic equilibrium where some water leaves the silica while new water sticks to it.
So, you can generally tell when non-indicating silica gel is saturated (for a given relative humidity and temp) based on mass. It’s not perfect since the absorption process is dependent on humidity and temperature, but it should be close enough for most uses.
A basic test would be to freshly regenerate some gel, record its weight on a cheap digital kitchen scale, and then leave it sitting out for a week. Measure the weight again and that will be your saturated mass. Then you know when your gel has gained that % mass, it needs to be regenerated.
I just leave the gel in the packets unless I have good reason to remove it. As long as the packets don’t have any metal, it should be fine to microwave them. Otherwise, an oven also works as long as the temp doesn’t go so high that it melts the packets (again, 120˚C should be enough).
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