Reusing Dessicant


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cbrgator
September 18, 2009, 12:47 PM
How hot and for how long do I bake it. My oven only goes as low as 170F. Is that ok?

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longbeard48
September 18, 2009, 01:01 PM
Put it on the dash of a car in the hot sun. Works for me.

Canuck-IL
September 18, 2009, 01:31 PM
The little (5" * 2") tin cans from Midway are listed as 3 hrs, 300 degrees.
I've often just put them in with something cooking at 400 and not observed any problems.

/Bryan

oneounceload
September 18, 2009, 01:40 PM
I do not mix them with anything - just put them in at 200 until the colors change back

loadedround
September 18, 2009, 01:45 PM
All desiccants are some form of anhydrous Calcium Sufate(plaster of paris or gypsum) and can be used over and over again. Normal recycling procedure is to put the desiccant in an oven proof container and heat it at 325-350 degrees for one hour and it's good to go again. A word of caution, do not use a microwave oven to dry your desiccant, since the moisture crystals have a tedency to explode in a microwave oven...just ask the dumb chemist who did it! :D

7X57chilmau
September 18, 2009, 01:55 PM
Silica Gel is not gypsum. Same treatment works, though.

I tend to make my own from drywall core, and I bake it out at 450F for an hour. Keep in mason jars untill needed, packed while still hot.

J

Mikee Loxxer
September 18, 2009, 01:58 PM
Silica gel is to be heated in a conventional oven at 300 degree fahrenheit for 3 hours. You can do this about three time before you need to replace it.

danprkr
September 18, 2009, 02:54 PM
If you have a vacuum chamber handy that might work to. I know, I know who has a vacuum chamber handy? But in theory it should work. I say this because I've been wanting to try it, but can't seem to make the time to build a chamber for my pump.

The only real concern I would have is that pulling the moisture out to fast would cause issues much like the microwave. But, you could probably get around that by stepping it down an inch of mercury at a time.

loadedround
September 18, 2009, 04:11 PM
7X57chilmau: I beg to differ with you but most desiccants are Calcium Sulfate and one of it's generic names is gypsum. Practically the same as the inner core of the drywall that you are now using as a desiccant. If you have doubts about the correctness of my statements, I strongly suggest you research Calcium Sulfate and prove me incorrect. You might want to start with Goggle as your search engine. :rolleyes:

damien
September 18, 2009, 04:32 PM
I have big cloth bags of dessicant and 250F works for me - about 3 hours each and the indicator will turn back from pink to dark blue.

I believe silica gel can be regenerated many more times than the three times stated above. I've done it many times more than that and it seems to not lose any potency at all, nor change appearance.

I have read that the dessicants that have the blue/red indicators will start to lose color after a few regenerations, though. Mine has the indicator external from the bag itself so that is not an issue. The ones I use:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=390090029474

I highly suggest these. Used them for years. The dessicant is in a cloth bag and the indicator is separate in the box. Remove the bag from the box and bake it at 250F for 3 hours and it is back to 100%. Don't go over 300F or the cloth browns. If you brown it too much, you have to find another cotton bag (the dessicant itself will survive).

Dravur
September 19, 2009, 12:47 AM
I use silica gel kitty litter. Tidy cat works the vest and you get a whole buttload of it for cheap. I pour some in a sock, hang it in the safes. Seems to work great. Heat it up, dry it out or give it to kitty.

The only downside is my guns like to scratch in the sand and meow a lot more

loadedround
September 19, 2009, 09:50 AM
One more comment about desiccants and I will shut my big mouth. Dessicants are chemical compounds and as such can not be altered by any physical means and that includes heat at a reasonable temperature. Bake iit at 500+ degrees and you will have desiccant oxide that will no longer do it's job. However keep the temp at 350 degress with a reasonable time and the desiccant can be used indefinitely. :)

fatelk
September 20, 2009, 12:07 AM
Silica gel is made from sodium silicate. Gypsum is calcium sulfate dihydrate. These are two very different substances. 7X57chilmau is correct.

The proper temperature, from my research when I was drying silica gel (found a good supply, dried it and sold it), is 245F. Much over 300F will damage it and it won't be much good after just a few times.

Gypsum based desiccants, I understand, can take more heat, as others have said.

otblue
September 20, 2009, 04:38 AM
I use both the silica gel and the calcium based dessicants. I much prefer the silica gel. If not overheated to "regenerate" it can be used indefinitely. The cheapest version available seems to be the kitty litter crystals. However because of their structure they are not quite as effective as the other commercial types but still more than adequate.
The stuff available downunder has blue crystal in it but these are NOT indicating, that is they do not change colour as water is absorbed so I usually sprinke in some of the real stuff to tell me when to regenerate.
Be aware that the silica dust is not good for you if inhaled and that the cobalt indicator is thought to be a carcinogen so don't regenerate the gel in the oven with your food.

loadedround
September 20, 2009, 09:04 AM
Otblue:
At no time did I mention silica gel. Most desiccants used for moisture control is anhydrous Calcium Sulfate; plain, and indicating that contains Cobalt Chloride for a blue to red color indicator showing when to regenerate. Desiccants purchased from Brownell's or Midway are all Calcium Sulfate based. I stand by my original statement.

fatelk
September 20, 2009, 12:00 PM
loadedround, I don't mean to be argumentative or distract form the original question in this thread, but I think you might have misunderstood.

You're saying that you stand by your original statement, but your original statement is that "All desiccants are some form of anhydrous Calcium Sufate(plaster of paris or gypsum)". This is not entirely correct. Your later statement that "most desiccants are Calcium Sulfate" is more accurate and defensible.

7x57 simply pointed out that silica gel is a desiccant and is also not Calcium Sulfate, and you kind of jumped him for it. I don't think anyone has tried to attack your veracity, just point out a simple oversight; no need to get defensive.

I make mistakes all the time, and appreciate it whenever someone politely points it out.:)

jakemccoy
September 20, 2009, 01:29 PM
The kitty litter route will probably be cheaper than running your oven at 300 for 3 hrs. In other words, instead of regenerating old packs, toss the old packs and replace with new kitty litter packs.

For those who don't know, you can buy kitty litter at Walmart that's the same material as what's inside the dessicant packs. You just have to spend some time and read the labels. It says "silica gel" somewhere on the package. You take the kitty litter and pour some into the ankle high pantie hose, which you can also get at Walmart in bulk and for cheap. Tie a knot in the pantie hose and you have a dessicant pack that's as good as any other. The extra kitter litter stays in the thick plastic bag that it came in from Walmart.

If you compare the pricing on this kitty litter system, you may get pissed about how much you've paid for the marketing of the more sophisticated dessicant packs. You could bake the kitty litter if you wanted, but the material is so inexpensive that the cost running the oven is probably more expensive than just starting fresh.

4v50 Gary
September 20, 2009, 01:31 PM
If you have a gas oven, just let it sit there for a month. Why bother even to turn it on? Let the pilot light do the work.

dev_null
September 20, 2009, 06:25 PM
Gary:

Well, that's one way to keep your oven dry. Doesn't do much for your gunsafe, though. :evil:

otblue
September 20, 2009, 06:39 PM
Loaded round, a quick check of both Midway and Brownells shows that the dessicant packs they sell are silica gel based.

Gary, I take it your wife doesn't cook much.:)

billwright
September 21, 2009, 10:35 AM
cbrgator:

It really depends on the Silica Gel or Desiccant product that you have. Desiccant comes loose, in packets, in canisters, in plastic packets, etc.

What you need to do is find the manufacture of this product you have and inquire with them to see the specific reactivation instructions with that company.

Keep in mind the Blue Silica Gel is not good stuff, it contains Cobalt Chloride which is listed as a Hazardous Material in the UK.

If you have "blue" Silica Gel consider replacing with the "Orange" indicating silica gel as this does not contain Cobalt Chloride, as shown here:

http://www.silicagelpackets.com/loose-silica-gel/

7X57chilmau
September 21, 2009, 01:45 PM
:rolleyes:

paradox998
September 21, 2009, 09:06 PM
The kitty litter silica crystals work well and go for about $7 for 10lbs. Go to ebay (unfortunately) or a craft store and buy some small muslin bags. Put a small scoop in each bag and you have instant dessicants. You can warm them in an oven to recharge them. I put them in the oven at about 225 for 3 hours to dry out, but I am not sure the time is that critical.

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