Silica Gel Drying

So it’s time for the whole pile of silica gel to go into the oven. The various packages suggested something around 12 hours at about 250 °F, so I set the oven timer for 11:59 and let it cook overnight:

Assorted Silica Gels
Assorted Silica Gels

The granules in the trays go into sealed glass jars, where they will remain dry until needed. The assorted beads & kibble in the plates get bagged up and go in the fireproof safe along with the big bag in the front, where they ought to be good for maybe half a year. It’s a new safe, so we’ll see how that works out; I tucked a note with the weights inside the safe.

I found a “sealed” plastic bucket of assorted packages that I’d dried and weighed a decade ago and then lost in the back of the shelf. It had gained 2 ounces, but the packages have rotted out and the beads weren’t in good shape; they were the consumer-grade bags that aren’t intended to be dried and reused.


10 thoughts on “Silica Gel Drying

  1. Hmmmm… so I’m wondering where this leads? Some years ago I had the misfortune of putting steel stuff in a “fireproof” safe. I came back a few months later and it was all rusted. Turns out that many (including my) “fireproof” safes use a double wall, and the inside layer is packed with silica gel saturated with water. The idea being that if there’s a fire, the fire has to boil all that water before the inside gets over 100C. Side effect of that is that the inside of my safe ran about 100% humidity. So, are you going to use silica gel to dry the air made humid by saturated silica gel? Anyway, my safe is now a printer stand.

    1. the fire has to boil all that water before the inside gets over 100C

      That’s true for the “media safe” out in the garage, but this one seems to have a solid plastic liner with a seal around the lined door. At least to a first approximation, the concrete / gel / gunk in the double-wall outer shell should be isolated from the interior.

      Now that you mention it, though, I should toss a data logger in there and record the humidity for a while. Dry silica gel should hold it at about 40%, which is enough below the basement’s (expensively maintained) 55% to make the gel’s end-of-life obvious.

      Thanks for the reminder!

  2. I usually put the silica paper bags directly on my lab hotplate and set it to 60C (arbirary value IMHO, probably low heat setting) and cover the bags with a 2L beaker. You can see the water condensing inside the beaker. I wipe it off every few hours till I see no more condensation. Now they are ready for re use.

    1. I like the direct feedback: heat until the water stops coming out.

      Next time, that ancient aluminum griddle / hotplate / warmer I use to warm PCB etchant should do the trick …


      1. Ed, there was some manufacturers who made colored silica gel. The color changed from blue to white. Heating would restore the color and that was a good indicator. At the farm during the rainy season we need it badly to prevent cameras and such from getting ruined from high humidity.

Comments are closed.