(There are lots of metal objects that are microwave-oven compatible.
Just checking that this might be one of them.)
Hi Robin.
In typical Brisbane (where I see you are) humidity, silica gel if exposed
to the atmosphere will absorb as much water as it is going to within the
hour or so. After that it is useless unless reactivated.
That indicator spot on the can should change from blue to pink in a
similar time under similar conditions.
If you have never reactivated yours because the spot has never changed
from blue to pink you would have to think that something is wrong with
the indicator and the crystals inside have saturated long ago.
gb.
For everyone else, after a bit of Googling, found this Qld based lab supplier (ProSciTech) that sells bulk silica gel e.g. 500g:$12, 2kg:$29.
That should last a lifetime.
http://www.proscitech.com/cataloguex...age=c8#c81-005
They also have a good Silica gel FAQs page:
http://www.proscitech.com/cataloguex....asp?silicagel
gb.