Rejuvenating silica packs.

[Mike Kennedy]

My local camera shop manager just gave me 20 small paper packs of silica gel that were included in shipments of camera gear.I've heard about heating them in the oven or microwave to bring them back to full strength.
A quick web search turned up some questionable results: 2 hrs. at 90c
Any ideas?

Thanks

 

[Craig]

That sounds about right. Look for flower drying sites, my Grandma used to have a big tin of silica gel she used for drying flowers, and she rejuvinated it by putting it in the oven on low heat.

 

[mgb74]

I'm not so sure about the microwave, but the oven method works. I've seen varying recommendations on time and temp. I generally do 2-4 hours (depending on size) at 225f if it's not in paper. In paper, I'd go longer but not as hot.

BTW, I have some large packs (about 3/4 or 1 lb each) that originally came packed with motorcycles being shipped from Japan. Don't know if that's still a source or not.

 

[amuderick]

I'll second mgb74. A few hours just below the boiling point of water will do the trick. I'd skip the microwave. The heating is uneven.

 

[Vaughn]

Paper packaging should be fine at 225F. Ignition temp of paper is 451F -- hence the book by the same name...Farenheit 451, by Ray Bradbury.

Vaughn

 

[iamzip]

I am pretty sure you can buy silica gel fairly easily and inexpensively. Not sure if it's really worth the hassle of rejuvinating, especially if you are unsure. You wouldn't want to risk any equipment!

 

[mgb74]

I've always assumed, perhaps incorrectly, that it's not the heat per se but the drying out in the oven. So I'm not sure how the microwave would work.

Some silica gel (though not the stuff already in packets) has indicator "beads" that change color when reactivated.

 

[Chazzy]

I am pretty sure you can buy silica gel fairly easily and inexpensively. Not sure if it's really worth the hassle of rejuvinating, especially if you are unsure. You wouldn't want to risk any equipment!

I see the little packets in bottles of prescription drugs, but where can a person go out and buy them?

 

[richard ide]

IIRC Lee Valley sells several sizes.

 

[kaputnik]

"pelican" makes handy re-usable silica packets for cameras and electronics. They cost around $15. They can be re-charged by cooking them in an oven at around 300 degrees for a few hours or until the colour changes from purple to red.They're great for traveling except when you need an oven to re-charge them.

 

[Mike Kennedy]

Thanks all!
Normally I'd toss them but I must make every penny count in the coming months.Just had a new roof installed on the house.Total build cost,around 890 rolls of Tri-X.

 

[benjiboy]

I just get my oven warm, turn it off , and put them in for a couple of hours.

 

[tac]

I always used the indicator (color change) type, bought in bulk, wrapped in typing paper-masking tape, all in an open freezer-strength plastic bag. A couple minutes in the microwave restores it just fine. Served me well for months in the sub-tropics of southern Japan. Does tend to fracture and powder, though.