can you reuse silica gel?

[voicilesrosbifs]

I'll bet the answer is no, but can you reactivate the stuff once it's absorbed moisture? Like, stick it in the oven or something? Seems such a waste.

What's the chemistry involved, anyway?

 

[RAI]

I'm guessing

Maybe the water can be driven off by putting the bag of silca gel in an oven set at just over 100 degrees. I'm guessing it's absorbed and not otherwise chemically bonded.

Aha! Wikipedia says 120 degrees C for a couple of hours to regenerate it.

 

[agurney]

I'll bet the answer is no, but can you reactivate the stuff once it's absorbed moisture? Like, stick it in the oven or something? Seems such a waste.

What's the chemistry involved, anyway?

Yes, just leave it in a dry place, like an airing cupboard, for a while.

I don't believe there's any chemistry involved, it just likes water (hygroscopic). Put it in a dry place and the moisture goes elsewhere.

 

[rjp]

Yes, just heat it gently in the oven to drive moisture off.

 

[Ruffles]

I'll bet the answer is no, but can you reactivate the stuff once it's absorbed moisture? Like, stick it in the oven or something? Seems such a waste.

What's the chemistry involved, anyway?

Yes you can. I used to keep 6 half kilo bags of the stuff on the boat in winter. I 'dried' it out on top of the hot water tank at home. Most silica gel has a colour indicator in it that goes pink when 'wet'. Not sure it will dry in a gas oven that well as the flame produces water.

I stopped using it when I considered that judging by the weight change it can't be absorbing that much water. My dehumidifier will extract a few litres before the humidity stabilises.

 

[old_salt]

Yep have a look here:-http://www.ehow.com/how_4686357_recycle-silica-gel-packets.html

 

[Downsman]

In the back of my state of the art depth sounder ( Marked in Fathoms ) Is a little screw in container with Silica gel in it. The book says..." When this goes pink place in oven ( The container not the book) until colour change. Seems to work ok.

 

[electrosys]

Clear (kinda white-ish) silica gel is much cheaper than self-indicating, so a neat economy tip is to keep a small quantity of self-indicating right next to the white stuff - likewise when re-generating in an oven. I find 90 mins at around 120 degrees to be about right - just keep an eye on the colour change the first time you try drying-out.

Now - for a really cheap source of silica gel - take yourself off to Tescos and look for Bob Martin's absorbent cat litter crystals - 'tis silica gel but in a bulk packet. For a 'working container' - drill a few dozen small holes in the plastic lid of a coffee jar, and you're good to go.

 

[Ex-SolentBoy]

Clear (kinda white-ish) silica gel is much cheaper than self-indicating, so a neat economy tip is to keep a small quantity of self-indicating right next to the white stuff - likewise when re-generating in an oven. I find 90 mins at around 120 degrees to be about right - just keep an eye on the colour change the first time you try drying-out.

Now - for a really cheap source of silica gel - take yourself off to Tescos and look for Bob Martin's absorbent cat litter crystals - 'tis silica gel but in a bulk packet. For a 'working container' - drill a few dozen small holes in the plastic lid of a coffee jar, and you're good to go.

Ingenious, but doesn't that encourage cats onto the boat, with unpleasant consequences.

 

[Ubergeekian]

In the back of my state of the art depth sounder ( Marked in Fathoms ) Is a little screw in container with Silica gel in it. The book says..." When this goes pink place in oven ( The container not the book) until colour change. Seems to work ok.

That's probably some cobalt chloride, which is blue when it's anhydous and pink when it absorbs water.

 

[Downsman]

Thanks for that UG, think you're correct, mine definitely goes pink when needing a reheat.......'ang on should I alter that sentence..

 

[electrosys]

That's probably some cobalt chloride, which is blue when it's anhydous and pink when it absorbs water.

Cobalt chloride is reputed to be toxic, so there's a predictable H&S drive towards supplying other indicators - orange to green, or orange to clear.
But - cobalt chloride withstands far more re-drying cycles than the new stuff - so it's much to be preferred if you can get it.

 

[voicilesrosbifs]

Thanks for that UG, think you're correct, mine definitely goes pink when needing a reheat.......'ang on should I alter that sentence..

Well, it's starting to go stiff after about a week in the bilge. No colour change, though - I must have the cheap stuff. Thanks for all the ideas... I'm off to the oven with it.

 

[Steve_N]

My self-indicating sachets came with instructions to dry them in the microwave.
A couple of minutes on full power and they change back to dry colour.

 

[electrosys]

My self-indicating sachets came with instructions to dry them in the microwave.
A couple of minutes on full power and they change back to dry colour.

A quick bit of feedback on this - I was a tad leery of doing this in case the crystals exploded - but no - it works like a charm.
This morning I've dried-out several kilos in less than 20 mins - a job which used to take me a whole morning - not to mention the leccy I've saved. Many thanks for the info.