Everyone knows those small bags of forbidden “Do not eat” candy that come with fresh rolls of FDM filament as well as a wide range of other products. Containing usually silica gel but sometimes also bentonite clay, these desiccant bags are often either thrown away or tossed into bags of FDM filament with a ‘adding one can’t hurt’ attitude. As [Stefan] over at CNC Kitchen recently figured out, adding an already saturated bag of desiccant into e.g. an airtight container with a freshly dried spool of filament can actually make the humidity in the container spike as the desiccant will start releasing moisture. So it’s best to dry those little bags if you intend to reuse them, but what is the best way?
Among the ‘safe’ contenders are an oven, a filament dryer and the ‘filament drying’ option of [Stefan]’s Bambu Lab FDM printer. These managed to remove most of the moisture from the desiccant in a few hours. The more exciting option is that of a microwave, which does the same in a matter of minutes, requiring one or more ~5 minute sessions at low power, which effectively also used less power than the other options. Among the disadvantages are potentially melting bags, silica beads cracking, the bentonite clay desiccant heating up rather dangerously and the indicator dye in silica beads may be damaged by the rapid heating.
After all of this testing, it would seem that there are many good options to reuse those desiccant bags with a bit of care, although for those who happen to have a vacuum chamber nearby, that might be an even faster option.
They’re too small to keep around IMO. But if you have a need methinks putting them in the sun takes care of them.
What about using a food dehydrator? (I don’t have the ability to test that myself)
It will likely perform similarly to the filament dryer.
i didn’t know they an indicator dye in, I guess mine have aways been “dry enough”
i used a lot of desiccant living in rain forest conditions (se alaska). i usually dry them on my gpu exhaust, in my network cabinet or sometimes in a light fixture. its generally on a leave them there until you need them basis, so they are usually pretty dry. never had to dry silica right now, and never thought to use a microwave.
I’ll eat them if I damn well please!
Not that I have any need to it, but couldn’t one use them to make Aerogel by soaking up as much water as possible, then freeze drying them or using a vacuum outgasser? I wonder if there’s anything useful that can be done by then spluttering them with metal?
they are not really toxic, they just print that on there so they are off the hook when a kid thinks its a pack of chicklets and chokes on it.
In the lab, we dry them in an oven at 80°C for a few hours and store them in airtight containers afterwards. In many of our applications we move to molecular sieves instead, but these can’t be dried.