I have a questions I haven’t found answered anywhere, but maybe someone here can help out.
First, some background:
I have bought this silica gel with indicator a while ago and have used it in my AMS and also for storing my filament in ziplock bags.
I now want to dry some of the silica gel, and have looked at the various options there are. I want to rule out the use of my kitchen appliances, as I am not fully convinced of the silica with indicator being really fully non-hazardous. I also recently bought a Creality Space Pi dryer, which I would like to use for drying my silica as well. Of course I would need to print a container for that, and since I only have PLA and PETG available at the moment, I wouldn’t be able to drive the dryer too hot.
Online you can find many different opinions about the ideal drying temperature for silica gel, ranging from 60°C to 145°C.
Efficient energy usage is no big concern for me with this, as my PV modules produce a lot of excess power during the current season.
Question:
What temperature should I dry the silica gel at, and does a longer drying time at lower temperature equal the same results as a quicker drying at higher temperature?
Or does higher temperature actually remove more humidity overall, which a lower temperature can maybe not achieve regardless of time?
I dry my silica gel in a convection toaster oven at 125°C. I put a temperature probe in the bottom of the tray. The temperature will hold around 100°C while it’s drying and jumps up fairly quickly when it’s done. It usually takes around 90 minutes.
Don’t put indicating silica gel in anything you will use for food, it’s toxic. Some types are less toxic than others, but none are completely safe. I picked up a used toaster oven and baking tray from a thrift store and marked then “not for food”.
A little tip for when you try out different methods: Check the weight of the silica gel, to check your progress.
For example: Take a container from the AMS, weigh it. Give it an hour in a food dehydrator. Weigh it. Repeat until weight no longer drops. Give it a couple hours or more in an oven that’s at least 100 °C. Then weight it again.
Now you know how long it takes in the dehydrator, and how well it works.
Later you can weigh it again, and compare to the weight out of the oven. Now you know how much water is in there.
The scientific method, eh? 😄
I microwave mine in a ceramic bowl on 30-40% power (in an 800w unit) for 20-30min, stir and give it another 20-30min. That usually restores them to a dry state and doesn’t cause issues with overheating them.
This is the only way I’ve been successful with a microwave dry. For a standard 1000-1100 watt microwave, drop the power down to 20%.
I normally toss them into my food dehydrator while I’m drying filament rolls though so I don’t need another step.
lower temps work partially afaik and they will never fully dry the silica gel. You should aim for above 100°C
If you are concerned about safety have one dedicated oven dish for the silica gel and ventilate your oven and kitchen thoroughly after a session.
I do this, I have a toaster oven that lives in my garage solely for shop use. Have some foil to act as a bit of a heat deflector, seems to work well enough.