Desiccant FAQ

Nan's Nook : Archives : Drying/Storage : Desiccant FAQ
  Subtopic Posts Updated Creator
Silica Gel  7 12/03 09:04am  
CaCl2  27 12/16 06:03am  
Drierite (CaSO4)  8 12/03 08:48am  

By Nan (Nanook) on Saturday, December 15, 2001 - 09:58 pm:

My Findings on Desiccants
by ShroomGod

I have tried three desiccants:

1) Silica Gel

2) Anhydrous Calcium Chloride - CaCl2 (DampRid)

3) Anhydrous Calcium Sulfate - CaSO4 (Drierite).

Here's what I found:

One can find silica gel in some larger craft stores for flower drying. It costs between $10-$20 for 5 pounds of the flower-drying-type silica gel. Silica gel will bring down the relative humidity of a closed container to about 40% while it is doing its job, and is a fairly good desiccant.

The white crystals are simple silica beads so are no more toxic than beach sand. One notable exception is the dust of broken beads, which is harmful to the lungs (like asbestos fibers). It should be noted, however, that a very small percentage of the crystals are of the indicating type and contain up to 1% cobalt chloride (Click here for a material safety data sheet for indicator silica gel crystals). This bad stuff is a heavy metal salt and is toxic and carcinogenic. It is there to turn these crystals blue when they are active (i.e. dry) and light pink when they need to be recharged.

The beads are not soluble in water, so they will not dissolve in your mushrooms like, for example, DampRid (calcium chloride). Never the less, don't let your mushrooms touch the tiny crystals because they tend to get stuck in the mushrooms, and the blue ones in particular are not good to eat (heavy metals are bad).

When the indicating crystals in Silica Gel turn from blue to light pink, the beads need to be recharged. To recharge them, place the beads in a shallow pan in an oven at 250°F for about five hours. Any higher heat than 250°F will cause excessive beads to fracture and turn to silica dust which is, as I mentioned above, bad for the respiratory system.

Anhydrous calcium chloride (the active ingredient in DampRid, Damp Gone, Damp Out and a host of others) is a slightly stronger desiccant. It is also cheaper. Locally, I can find this stuff at ACE, Home Depot, or other hardware (paint dept) in the economy refill size of 48oz (3lb) for $3. I find that it will often bring down the relative humidity of the inside of a closed container with mushrooms to 25% or even less while it does its job.

On the down side, this desiccant is very hard, if not impossible, to re-use. It tends to dissolve in the water it absorbs from the air, so when you try to dry it out, it often dries to useless, large chunks rather than to its original form of small beads. Also, it is highly soluble in water so that even if you place your mushrooms on paper covering it, it will still find a way to get in your mushrooms. On the other hand, it is not toxic like the silica gel indicator crystals. Still, if you have the unfortunate experience of eating some DampRid, it tastes like shit and will make you as thirsty as hell (will set the stage for a really bad trip).

The last type of desiccant I tried is anhydrous calcium sulfate (Drierite). Drierite is quite expensive ($10 a pound for indicating and about $7 for non-indicating). It comes in indicating which, like the indicating silica gel beads, turn blue when dry and pink when it needs a recharge. It also comes in a number of rock sizes, but I have no idea which size is best for drying mushrooms. The grade I used was about like aquarium gravel.

I have not looked over the toxicity of Drierite, but if I had to guess, I'd guess the indicator is the toxic cobalt chloride salt. I definitely keep it away from the mushrooms. I don't have any humidity readings on this desiccant either, but I found it to be about average strength. Again, once the indicating rocks (and you should buy at least some of the indicating type) turn from blue to pink, it is time to recharge. To recharge this desiccant, see the CaSO4 page.

I liked the fact that Drierite didn't turn to goo like DampRid and can be recharged, but it was just too damned expensive for my tastes. I used it a few times, but wasn't too impressed considering the price.

In general, the key to using any desiccant is to first fan dry the mushrooms. Buy a cheap fan, and place the mushrooms on the grill of the fan so air blows through the pile for 24 to 48 hours. If you live in a dry climate (40% relative humidity or lower) your mushrooms will dry completely out using this technique and you won't even need a desiccant. If you aren't that lucky, you should continue the drying process using a desiccant. Just place the mushrooms on a screen right above the desiccant of choice in an airtight container. If you want to push your desiccant to warp speed (several times faster), use a tiny fan on low speed inside the airtight drying container to gently circulate the air.


Desiccant & Indicating Desiccant Edited by Nan

Straight up calcium salts such as calcium sulfate and calcium chloride are relatively non-toxic. Eating some may actually contribute to your calcium MDR (but don't eat it) BTW calcium carbonate is preferred as a human dietary suppliment because it does not absorb water. The sulfate and chloride ions from desiccant salts are not going to bother you.

A little is not going to hurt you, just don't deliberately ingest it. Laying down a napkin on some non-indicating desiccant and cracker drying shrooms over it... Not a problem.

The indicating stuff is another story

The indicating silica gel (the most commonly used contains a small percentage of cobalt chloride coated particles) is known as being a substantial health risk esp. as a carcinogenic is being phased out/banned in Europe. There are new indicating compounds available which are organic and non-toxic, but I'm not sure if you can buy them yet.

In any case I would be very diligent in not letting drying mushrooms come in contact with the indicating silica gel. Place a screen or mesh over the indicating desiccant and lay your shrooms on that.

From the label of desiccating silica gel kitty litter:

"Non-Toxic and Safe Space Silica Litter is made from sodium silicate which is inert, non-toxic and biodegradable. Sodium silicate is used as an ingredient in the manufacture of many products, including soaps, detergents, and as a food additive. Its safety is unquestioned, and sodium silicate is used to eliminate moisture and protect food, pharmaceuticals and medicines during shipping. Space produces almost no dust, unlike clay litters, which can produce dust and have been known to cause respiratory problems in people and pets."

I also would assume that if it was used for cats and it were dangerous that it wouldn't last long in the pet stores.

Anyway, until they say I can eat it for lunch, I'll just keep a barrier in between our friends and the desiccant.

With that out of the way, we here at Nan's Nook have determined that the best way to dry shrooms is to place them under a fan at room temperature for 48 hours or so and then place them over desiccant in a Desiccator for another 48-72 hours. If the desicant is fresh, your shrooms will be "Cracker Dry" (the standard) in 4-5 days with no loss of potency. If you don't follow the Tek... You can expect problems.

9er Tek Tips (btm page) : Alien Tek (btm page) : Drying & Storage Teks : Desiccator : Drying Q & A : Shroom Glossary

By Brad (Raze) on Thursday, November 15, 2001 - 10:16 pm:

You can find CaCl2 in some ice melts...

By Tripster (Tripster) on Thursday, November 15, 2001 - 10:26 pm:

Just so you know, Silica gel can also be found in Cat Litter, which can be found almost anywhere and is pretty cheap.

By Lzmaryann (Lzmaryann) on Monday, November 19, 2001 - 03:26 am:

My foaf rigged a food Dehydrator by disconnecting the lead to the heating element. I had doubts at first but it worked great! I assume that the humidity levels in your house are lower than outside otherwise you will not accomplish much. I would leave the dehydrator on for a couple of days until you find a decent desiccant. I really don't believe the dehydrator will completely dry the product. So try to find some calcium chloride.

By Snoopy (Snoopy) on Monday, November 19, 2001 - 07:21 pm:

The way that I dry, which I have read before is that first I take the shrooms, cut the caps off and quarter them. (Cut into 4 different sections) And then usually depending on how big the stem is I cut that in half and sometimes then cut those halves in half. Resulting in 12 peices for every shroom. I place the cuttings inbetween 2 screens that I yanked out of my window, and put a fan laying on its back pointing up and blowing through the screen. The shrooms will 'appear' cracker dry in about 10-12 hours. But if you put them in a ziplock bag they get soggy in a day or so. So then I got a big tupperware container. ANd spread DAMPRID all along the bottom, and cut a screen and laid that ontop of the damprid and just throw all my shrooms in there after 10 hours in front of the fan. Store them in this container until its time to eat. I swear by this method its simple, effective, and cheap.

By Nan (Nanook) on Tuesday, November 20, 2001 - 02:03 am:

Good Tek, Accurate

By Lzmaryann (Lzmaryann) on Tuesday, November 20, 2001 - 03:25 am:

my foaf has found that cutting the shrooms tends to produce a pretty ugly looking mess when it's dried. Because of the bruising it looks quite dark and stringy. I don't suppose this makes any difference but you should know what to expect.

By Snoopy (Snoopy) on Tuesday, November 20, 2001 - 01:26 pm:

Yah they don't LOOK like shrooms... but your stomach doesn't care and it garuntees or gets closer to garunteeing that they are dry and don't rot on yah.... Me personally I don't care what the shrooms look like so long as they keep their magical properties.

By Piss Chill (Catfishjohn) on Friday, November 23, 2001 - 02:35 pm:

Well I found Calcium Chloride and it worked great! I've never seen such dry shrooms. Haven't tried eating em yet in this state but they seem much more appetizing. If anyone else lives outside the states and is having trouble finding the Calcium Chloride, I finally found it at a swimming pool supply store. Thanks for all the help folks!

By Nugdumper (Nugdumper) on Thursday, November 29, 2001 - 07:36 am:

So what does a person do if their local hardware store or Wally World doesn't cover one of these desiccants? I live in the midwest, and it is tough to find anything to dry with. And fan drying isn't very professional, and obviously not the best way to do it. I'd love to find good desiccant, anyone got suggestions?

By Paradox (Paradox) on Thursday, November 29, 2001 - 03:08 pm:


go to crafts/nursery store. They sell silica gel for drying flowers. I think silica gel is better than calcium cloride, cause it doesnt lump up when damp and can be easily microwaved to reuse it.

By Nugdumper (Nugdumper) on Thursday, November 29, 2001 - 10:37 pm:

You think a place like Hobby Lobby might have what I need? What about this cat litter thing? Do all cat litters work like desiccants, or certain brands or what?

By Brad (Raze) on Thursday, November 29, 2001 - 11:29 pm:

Yeah, I just found silica this week after tons of searching. Its a small store, just a craft store. It was right by the counter, I wasnt even looking for it when I spotted it (go figure).
I did also see it at "Michaels" a few weeks back, but I had no money on me. Its a big craft store chain (in Canada, not sure about elsewhere)

By patoban (Patoban) on Friday, November 30, 2001 - 12:06 am:

i found Damprid and several other similar products in the paint section of home depot

By Snoopy (Snoopy) on Thursday, November 01, 2001 - 03:00 pm:

I picked my shrooms last night , and put them between two screens above a fan. This morning I remembered that they can dry faster If I slice them in halves. So I did, and like 5 mintues later it looked like the insides were turning blue. This isn't mold is it but rather just the shroomz brusing correct?

By quote: (Quote) on Thursday, November 01, 2001 - 03:05 pm:

yup, you are correct.
no way mold could grow that fast anyway,
it's just the 'magic' oxidizing.
perfectly normal and nothing to fear.

By Dean Dichau (Impalerzz) on Friday, November 23, 2001 - 07:19 pm:

I am getting some pretty healthy shromms, and am using the Tupperware/dessicant/screen method of drying that everyone reccomends...
1.- Is there a reason these things are shriveling up beyond belief???
2.-Ive never seen shrooms so skinny in my life....Am I losing potency by drying this way????

Ive eaten some dryed and very fuzzy shrooms before and they were the best I've ever eaten. The insides of the stems has a fuzz that was different from any Ive seen. 1.5 grams and I was watching wood grain moving around..Im trying to achieve this, and am just wondering if it was a drying method...
.thanks all

By yagshroom (Yagshroom) on Friday, November 23, 2001 - 07:43 pm:

As long as you air dry them over a fan with cold air first before you stick them over dessicant, you should be fine. Sticking them over dessicant right away is almost asking for rot, especially if they are rather wet. It just can't suck enough water out fast enough... it is good for sucking the remaining water out that air drying couldn't take care of. The only way that drying is going to really effect your potency is if you dry them with hot air. Don't do that. As far as how small they are getting, that is normal. Normal mushrooms are 90% water, and if you had very wet substrate and got some impressive looking fat ass shrooms, they are more like 95% water. So when it comes time to dry, they are going to shrivel like hell, and will only weigh 1/10 to 1/20 of what they did fresh. If you are picking them at the right time, you should have nothing to worry about. Picking just before the veil breaks is by far the most important potency per gram aspect of growing.