Can any kind of desiccant pack (silica gel) be "recharged"?

I know there are some previous posts about desicccant packs (silica

gel packs) and about recharging them. Several suggest putting them

in the oven for a couple of hours at around 200 degrees. My question

is for clarification. Does this work for any desiccant pack that

contains silica gel, like the packs that come in shoe boxes or some

food products? Or can only certain kinds of desiccant packs be

so "recharged". Because if it's the case that any pack will work,

I've already got lots of silica gel packs just waiting to protect my

camera gear! Thanks.

You can redry silica gel dessicant by heating in an oven at 250 degrees for a couple hours to drive off adsorbed water. This should work with any dessicant that's actually silica gel (which should be pretty much all of the ones that come in small, "bean bag" containers with consumer goods).

The ones i have / i've seen are all in paper bags. I wouldn't heat them up to 200+ degrees like this. OTOH, you can unpack, do it and pack them in cloth or simple tissue "bags" you make.

<< The ones i have / i've seen are all in paper bags. I wouldn't heat them up to 200+ degrees like this. >>

 

There's a rather famous book whose title will instantly tell you why you are wrong and that 200 degrees is not a problem for paper.

I've done it a few times. 200-250 deg F is no problem for the paper as long as it's not too close to the element. What happened to me was that the glue melted and all the dessicant started leaking out. If you can find a better bag or perhaps staple over the glued seams it can work.

 

Cheers,

"Fahrenheit 451" by Ray Bradbury for those not familiar with American literature.

Keep in mind that Fahrenheit 451 is science fiction, written by the same man that told of the continual (water) rains on Venus and the ruins on Mars. Highly doubtful that every kind of paper known to man bursts into flames at exactly that temperature.

<< Keep in mind that Fahrenheit 451 is science fiction, written by the same man that told of the continual (water) rains on Venus and the ruins on Mars. Highly doubtful that every kind of paper known to man bursts into flames at exactly that temperature. >>

 

Who said anything about exact? Any reason you felt the need to troll?

>"to drive off adsorbed water"

 

I know this is being a bit pedantic, but isn't the water ABsorbed - i.e. right into the material, rather than ADsorbed - which means into the surface only? Ross

If you don't like the oven idea, there's always putting it in the sunlight, or perhaps leave it under a desk lamp. Or maybe leaving it in an "EZ-Bake Oven." :)

"Im aware of his work!"

- Martin Prince

Chunks of 2x4's also absorb moisture; and get lighter when died in a home oven. Tobacco; paper; beans also work too. Some military devices use a clay like material; held in a bag. Silica gel is easier than wood chips. A household oven has alot of radiation; that cause local heating of a silica bag. Place it in a pan; to avoid direct radiation on the packet. The packets get charred; or browned; and sometimes moderate oven temperatures; if the ovens coil directly is in sight of the packet. A scale can be used to measure the wet and dry weights; to see if the bag has alot of moisture still in it. Tell tale pellets turn to blue; from pink; when most of the moisture is gone. Military gear uses the term " XX units"; to determine the size of the bag required.

the whole concept of cooking silica and then cooking your food kind of sounds disgusting. :)

 

his place sells a bunch of different kinds including the clay that someone mentioned.

 

for the packs: http://www.desiccare.com/cgi-local/SoftCart.100.exe/online-store/scstore/shop_small_absorbents.html?L+scstore+lqbg2982fffec6fe+1085546737

I went to www.dehumidify.com. They have small dessicant containers made of metal that hold silica gel and have an indicator to tell when they need recharging. They are great, and one that would do a camera bag or cabinet costs about $6 plus postage. Recharge in an oven for 3 hours and tou are ready to go again.

Why to use Silica gel? Somewere I read some rice would be a proper substitute and an excelent emergency ration. Those in fear of the paperbags should sew the stuff into cotton.

I wouldn't recommend rice in connection with camera gear. The dust from rice is starchy, and forms a glue similar to wallpaper paste if it gets damp after escaping the packet. Instead of protecting your cameras, you could be speeding the gumming up of shutters and diaphragms. And even if this doesn't happen in storage (where everything presumably remains reasonably dry) it only takes one incident of condensation in the equipment (as from using it in cold weather, then bringing it into a warm room, or taking it cool from the case into hot, humid conditions, or even from breathing on it) to cause the problem.

:o) You know what, i just tried it for fun. I baked a small paper bag full of silica gel for 30 minutes in an oven exactly at 200 degrees. CELSIUS, I mean. The paper bag got brown, stiff, and smells a bit burnt. Conclusion: i don't think it's a wise way to do it.

 

That's all I can contribute with; you guys can check the literature, scientific or fiction. Cheers.

I put mine in the oven with just the pilot light lit, close the door and the next morning they are dried and ready to absorb again. That way you don't get the crispy, brown paper. I've used mine for about six years now.

 

Conni