https://www.youtube.com/watch?v=6tHInlFfMcM
copy of the video description text:
Over the years, I've collected a lot of silica gel packages and regularly put them into my stuff, hoping that they will keep it dry. These tests showed me that there is more than silica gel in the typical desiccant packages and that if you don't properly dry them, they can even ruin your filament. Let's compare four different methods to keep your loose desiccant and your silica packages dry!
Chapters
00:00 Introduction
01:19 What's inside a desiccant bag?
01:54 Sponsor
03:19 Clay desiccant
04:57 Indicating desiccant
06:53 The problem with desiccant
10:26 Get rid of your desiccant bags?
11:06 Drying desiccant
14:38 Drying in a microwave
16:40 How much energy does it use?
19:34 Drying the bags in a microwave
21:48 Do you damage your desiccant in the microwave?
23:18 Summary
I'm surprised Stephan did not mention that bentonite clay is commonly used for cat litter.
I use industrial silicagel granules that I buy in 5-liter jugs. The granules are blue when dry and turn purple/red when they no longer absorbs humidity. Then I throw them in the microwave for 5 minutes and the granules turn blue again - and scalding hot too.
It's not perfect because it gradually turns more and more silicagel granules to dust as they explode like popcorn. So after maybe 10 to 15 cycles, the silicagel becomes ineffective and the blue granules turn more and more to brown, Then it's time to throw it away and use a fresh batch.
It's possible to extend the life of the granules by drying them in a regular oven at low heat rather than in the microwave at full pelt but it's slow and annoying, and silicagel isn't that expensive, so I don't bother.
I read somewhere, that the dye is either poisonous or carcinogenic (sorry, no source, I have to search for it again). So I am not sure if putting it in the microwave is the best idea.
Some (usually cheaper) indicating desiccants use cobalt-based dies which are fairly toxic, but unless you are using them to keep food dry it's not a huge issue. Having them break into powder in the microwave probably isn't great though, I'd avoid breathing any of it in
The orange indicating gel is less toxic, but it's still not good for you. Don't dry any indicating silica gel in the same oven you use for food. The clear silica gel is non toxic, but breathing the dust can cause silicosis.