Sciencemadness Discussion Board

Using a microwave to dry silica gel.

Mark Van Adium - 20-6-2011 at 02:51

Does this work well, it certainly gets hot, I'm just wondering how well aired it needs to be (is a pot ok or does it need to be on a plate?) and if it getting hot is directly correlated to it drying out.

Anyone have any experience?

blogfast25 - 20-6-2011 at 05:08

Use large enough quantities (MWs don’t like running on empty).

A non-UHF-absorbing PP dish or shallow pot is probably best.

Use fairly short bursts: 1 minute or so (on ‘high’), check temp., another minute etc, to avoid overheating.

Once at desired temperature, use low power to hold it there.

Check progress by weighing up the sample several times: constant weight would indicate water loss is complete.

And no: I have no experience with it and may well be talking through my other orifice. Worth experimenting with but make sure you clean the MW prior to food use.

IndependentBoffin - 20-6-2011 at 06:46

I once accidentally had my oven at 220C when drying silica gel, because I was previously using it to dry some calcium sulphate.

The indicator silica gel got charred, with the top layer on the tray looking black-ish.

Hotspots on microwaves are definitely a possibility. I'd stick to using an oven at 120C.

http://www.envirogel.co.uk/improving_silica_gel_reactivation...

Panache - 20-6-2011 at 16:41

don't run it directly on the glass plate as i shattered mine when drying molecular sieves in the microwave, if you are a good aim, a well positioned ir thermometer can read temperatures through the microwave grating on the front door. or you could just open the door.

cyanureeves - 20-6-2011 at 17:24

i microwaved silica sand with blue indicator crystals used for drying flowers and the fan blew fine dust all over inside my microwave.

IndependentBoffin - 20-6-2011 at 22:53

Quote: Originally posted by cyanureeves  
i microwaved silica sand with blue indicator crystals used for drying flowers and the fan blew fine dust all over inside my microwave.


http://en.wikipedia.org/wiki/Cobalt#Biological_role

Generally a bad idea to mix cobalt (from the indicator) with food...
Quote:

After nickel and chromium, cobalt is a major cause of contact dermatitis and is considered carcinogenic. In 1966, the addition of cobalt compounds to stabilize beer foam in Canada led to cardiomyopathy, which came to be known as beer drinker's cardiomyopathy.

LanthanumK - 21-6-2011 at 02:47

If the indicator was blue, why would you microwave it?

Saerynide - 21-6-2011 at 10:50

Put it in the oven on a cookie sheet at 250-275F and bake. I usually leave it for 30-45 min. Comes out dry enough that if i run my hands through it, I can feel my skin dry out and I have to grab the lotion

cyanureeves - 21-6-2011 at 11:09

Quote: Originally posted by LanthanumK  
If the indicator was blue, why would you microwave it?
no the crystals were always pink. i didnt know they had to be dried until blue.didnt know about cobalt either.

Finnnicus - 10-4-2013 at 02:08

I have lots of experience of drying with microwaves. Mind the balls cracking tho, but I highly recommend it!