Drying with silica gel

Has anyone tried using silica gel to dry Cannabis? From what I've read, it reaches equilibrium at about 35% water. So in theory you could absorb 35% of the water in the weed by using an equal weight of dried silica and the weed would come out as 65% moisture. Makes the ratios easy to remember, being exactly the same.

Why would I want to use the silica gel instead of open air? Smell, that's why, horrendous smell problems. So instead, why not keep all those terps contained in an airtight container so none of them get into the air? You would also get more fragrant weed.

A fairly large container would be in order, so the silica and weed could be in thin layers with high exposed surface area. I would put a screen above the silica with air space between, to put the weed on, and put a small PC fan in there to circulate the air. I'll try it next time actually, but for now it's just an idea. The silica gel is bought cheaply in the kitty litter section. The blue grains aren't really moisture indicating though, just fake dyed ones.

I guess I calculated that wrong. I equated RH with moisture percent. You really need weed to be probably 5-10% moisture, so you'd need almost 3 times the weight of silica as weed. You would just use an excess and monitor the RH. 3 times as much should do it. That would be 105% of the water in the weed, if it was possible.

I tested this with some leaf I had trimmed off. I put it in a paper bag. Filled a Tritan container about halfway with silica cat litter, put it in the microwave for about 2 minutes until it got hot enough to drive off much of the moisture that was already in it, mixing it around after I took it out too expose most of it to the air to dry it and cool it some. Then I put the bag of leaf in there on top the silica and put the lid on and closed the airtight locking flaps. Next day when I opened it there was quite a vacuum and I could hear the air go in as I cracked the seal. The leaf was completely dried and had lots of aroma.It was sort of a combined desiccant/vacuum drying.

I think it's best to put the weed in and seal it while still fairly warm like that. It will help get the moisture vaporized and create a vacuum when it cools, while at the same time making sure the silica is fairly dry. I tried it first with the cold silica right from the bag and after a day it was only partially dried. The second day with the heated silica completed the drying. The leaf was actually a little dried before I even put it in the bag though, in the shriveled stage but still plenty wet.

Anyway, does seem to work, at least with leaf. Should work with bud. I'm sure you'd have to re-dry the silica each day with the microwave but should be done after 2 or 3 such treatments. Whether or not it would get overly dry, I don't know right now. Could just rehydrate it though if it does. I would let the silica cool down until only slightly warm before sealing it on the last time though, when it's already close to dry enough, and not leave the buds in for a whole day before checking it again.

This is similar to a tek used for drying magic mushrooms. The way I did it with shrooms is using a box with a top and damp rid(unscented). I'm sure you could just use a bowl of silica gel in place of damp rid. Don't use damp rid for weed or it will get bone dry. I used a box my work boots came in. Cut a hole in the bottom of the box a bit smaller than the damp rid container so you can slide it in the hole without it going all the way through, so the lid sits just above the bottom of the box. You could place the damp rid/container of silica gel in the hole and place buds around the container and put the lid on the box. Prop the box up on 2 chairs so the container is hanging from the bottom of the box in between the 2 chairs. Let me know if this works on bud.
your chair box your other chair
chair ______ box ______ chair

Buy a small scrubber and booster fan and sit it in your drying room and that will take care of your smell problem. Don't make things more complicated that they have to be.

LegalizeNature420 said:

Buy a small scrubber and booster fan and sit it in your drying room and that will take care of your smell problem. Don't make things more complicated that they have to be.

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Yeah but is having buds out in the air really good for quality? You're gonna lose a lot of terps and some THC may also degrade.

BobCajun said:

You're gonna lose a lot of terps and some THC may also degrade.

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You're thinking too much. Just keep temperatures moderate and relative humidity around 50%.

LegalizeNature420 said:

You're thinking too much. Just keep temperatures moderate and relative humidity around 50%.

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No I'm thinking just the right amount. Drying with silica gel is the future. Simple air drying is uncivilized.

bertaluchi said:

This is similar to a tek used for drying magic mushrooms. The way I did it with shrooms is using a box with a top and damp rid(unscented). I'm sure you could just use a bowl of silica gel in place of damp rid. Don't use damp rid for weed or it will get bone dry. I used a box my work boots came in. Cut a hole in the bottom of the box a bit smaller than the damp rid container so you can slide it in the hole without it going all the way through, so the lid sits just above the bottom of the box. You could place the damp rid/container of silica gel in the hole and place buds around the container and put the lid on the box. Prop the box up on 2 chairs so the container is hanging from the bottom of the box in between the 2 chairs. Let me know if this works on bud.
your chair box your other chair
chair ______ box ______ chair

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Thing about Damp Rid (calcium chloride) is that it will keep absorbing water until the air around it reaches 22% rh. Now if you were to use sodium chloride, table salt, it would only get down to 75% rh. That's not far from the target rh for curing of around 65%. I suppose from the 75% point you could just use Boveda packs. As long as there are undissolved grains in the salt solution it will keep absorbing water until either it all dissolves or 75% rh is reached. There are other salts that get to a lower rh, like sodium bromide in the 50s. Maybe having both salts would make it get to a middle rh between the two. Never tried it. I find the dry silica more convenient to work with than solutions. It's bound to get spilled sometime.

BobCajun said:

Thing about Damp Rid (calcium chloride) is that it will keep absorbing water until the air around it reaches 22% rh. Now if you were to use sodium chloride, table salt, it would only get down to 75% rh. That's not far from the target rh for curing of around 65%. I suppose from the 75% point you could just use Boveda packs. As long as there are undissolved grains in the salt solution it will keep absorbing water until either it all dissolves or 75% rh is reached. There are other salts that get to a lower rh, like sodium bromide in the 50s. Maybe having both salts would make it get to a middle rh between the two. Never tried it. I find the dry silica more convenient to work with than solutions. It's bound to get spilled sometime.

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Yeah I don't recommend using damp rid for drying bud. Just used the example of drying shrooms to give an idea of a different set up.

55-62% is perfect for herb

bertaluchi said:

Yeah I don't recommend using damp rid for drying bud. Just used the example of drying shrooms to give an idea of a different set up.

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For mushrooms it would be great, because you want them bone dry. For weed, not so great, unless you watched it with a humidity meter.

Chillin chillin said:

55-62% is perfect for herb

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Interestingly, the common fertilizer calcium nitrate is very close to the right range for drying weed. Here's a quote from a page about using salt solutions to maintain rh in museum display cases.

"At the humidity range we were interested in maintaining, 55%-60% RH at 70 degrees F, two appropriate salts were listed in the Merck Index3: sodium bromide and calcium nitrate. Another salt, sodium nitrate, was just above that range. We consulted with John Twilley, Senior Research Chemist at the Los Angeles County Museum of Art, to determine whether either of these salts could present risks to art objects in a closed case. Since bromides have the potential to develop halogens at the vapor stage, sodium bromide was eliminated. We decided upon calcium nitrate as our test salt; it was in the correct humidity range and had been used successfully by the Viking Ship Museum for over thirty years with no ill effect to objects. Simple experiments with calcium nitrate solution are ongoing at the Seattle Art Museum to determine whether volatiles are escaping into the test case. Results will be reported in a future WAAC Newsletter."
http://cool.conservation-us.org/waac/wn/wn13/wn13-1/wn13-106.html

Here's a page with a list of various salts and the rh they produce. Cobalt chloride is right around 65%. Kind of toxic though and not convenient to source.

This didn't work out well with buds. I think the problem is that it's very hard to get the silica dry before using it. Microwaving takes some water out but clearly not that much. From what I've read, you have to put it in a regular oven at 300 for 6-12 hours. So obviously you're not going to get it out with just a few minutes of microwaving. It's also pretty dusty. All in all, probably not worth the hassle.

BobCajun said:

Interestingly, the common fertilizer calcium nitrate is very close to the right range for drying weed. Here's a quote from a page about using salt solutions to maintain rh in museum display cases.

"At the humidity range we were interested in maintaining, 55%-60% RH at 70 degrees F, two appropriate salts were listed in the Merck Index3: sodium bromide and calcium nitrate. Another salt, sodium nitrate, was just above that range. We consulted with John Twilley, Senior Research Chemist at the Los Angeles County Museum of Art, to determine whether either of these salts could present risks to art objects in a closed case. Since bromides have the potential to develop halogens at the vapor stage, sodium bromide was eliminated. We decided upon calcium nitrate as our test salt; it was in the correct humidity range and had been used successfully by the Viking Ship Museum for over thirty years with no ill effect to objects. Simple experiments with calcium nitrate solution are ongoing at the Seattle Art Museum to determine whether volatiles are escaping into the test case. Results will be reported in a future WAAC Newsletter."
http://cool.conservation-us.org/waac/wn/wn13/wn13-1/wn13-106.html

Here's a page with a list of various salts and the rh they produce. Cobalt chloride is right around 65%. Kind of toxic though and not convenient to source.

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After reading the article you linked I think your on to something.

house34 said:

After reading the article you linked I think your on to something.

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Yeah the salt solution thing would probably work. It's just slow, but if you normally take weeks to cure/dry then I guess it won't matter.

BobCajun said:

Yeah the salt solution thing would probably work. It's just slow, but if you normally take weeks to cure/dry then I guess it won't matter.

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A real benefit to be able to cheaply and easily regulate RH. Just keep temps at 70f and your good to go (in theory). I will definitely give it a try.

house34 said:

A real benefit to be able to cheaply and easily regulate RH. Just keep temps at 70f and your good to go (in theory). I will definitely give it a try.

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I'll be interested to hear about the results then. What salt are you going to use though, calcium nitrate?

BobCajun said:

I'll be interested to hear about the results then. What salt are you going to use though, calcium nitrate?

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Yes, a 50# bag is like $27. I haven't looked up Gore-Tex fabric yet.

house34 said:

Yes, a 50# bag is like $27. I haven't looked up Gore-Tex fabric yet.

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I wonder if it would help to put a bubbler in the salt solution to circulate the air through it inside the closed container. Just have to make sure the solution container is lightly covered so that the water droplets from the bursting bubbles don't get on the product.