Thread: DIY Drying Agent/Desiccant

Did you know that one of the most powerful drying agents used in organic synthesis can be purchased in nearly any supermarket? In fact, some of you growers have used the hydrated form of this substance to correct magnesium deficiencies in your gardens. I’m talking about, of course, magnesium sulfate (MgSO4)- the heptahydrate form you know as Epsom Salt (MgSO4•7H2O). Magnesium sulfate, like sodium sulfate, will chemically absorb water to rehydrate itself into the heptahydrate form. This can be very beneficial if you are drying wet chemicals or want to keep the inside of an airtight container dry during long term storage.

This DIY will teach you how to make, use, and store your own magnesium sulfate (although this method most likely produces the equally useful lesser hydrates such as Sanderite [MgSO4•2H2O] or Kieserite [MgSO4•H2O] ). You can use magnesium sulfate as both a drying agent and a desiccant. Uses include:


·Drying wet organic liquids
·Making 200 proof ethanol (at your own risk)
·Long-term storage of seeds
·Long-term storage of ammunition
·Drying of Herbs

For this DIY you will need the following:


·Epsom Salts – USP grade (supermarket)
·An oven that can heat to its maximum setting- 550°F (288°C)
·A non-stick metal pan (preferably new)
·A scale/balance if you want to weigh out a specific amount
·Airtight glass jars for storage
·Misc. utensils
·Eye protection (always good)




Set your oven to its maximum setting, which in my case is 550°F (288°C). To a non-stick pan, add a layer of Epsom Salts no thicker than 1 cm (about the diameter of a penny). Crumble any chunks and then shake the pan to evenly layer the salt. Any thicker and you will end up with a rock-hard layer on the bottom which can only be easily removed by washing in water. Don’t worry; this method will not harm the metal pan you are using.




Place the pan in the center of the oven and let ‘cook’. As the salt dehydrates it will boil off water. That hissing sound you hear is steam escaping. Periodically check to see how your future drying agent is doing- if you wear glasses you’ll notice they will fog up when you open the oven door. When the hissing stops and you no longer sense any steam being emitted your drying agent is done! Don’t worry if it comes out looking a bit gray in color; that is most likely the Kieserite (monohydrate) form of magnesium sulfate (nothing to worry about). I heated my ~590 grams of Epsom Salt for about an hour.



Using a utensil of your choice, lift up the cake of dehydrated salt from the pan to make sure it separates easily. Then, cut or crush the cake into bits small enough to make it into your canning jar. This should be done as soon as possible, as your drying agent will begin to absorb moisture from the air as soon as it leaves the oven. Then, immediately cap and seal your jar and leave it to cool. Be careful, as your drying agent is very hot and in turn it will make your glass jars hot. I was able to fit 590 grams of Epsom salt (330 grams dry) into two 16 ounce (1 pint) wide-mouthed canning jars. Wash out your metal pan with tap water and it should be as good as new.







There you go!

Now, you’ve made your drying agent, you’ve stored it, and you let it cool. Now what do you use it for?

Since this is a growing website, you may be interested in storing seeds for a long period of time. Seeds store best in cool dry conditions. Your fridge is the perfect temperature, but to make your storage container dry you will need a desiccant to keep the relative humidity low. To store seeds for long periods of time, you will need an air-tight container, a coffee filter, and a twist tie. Simply scoop some of your desiccant into the filter, secure with a twist tie and you have a desiccant bundle which will keep the humidity very low in your container.






Seal your container, place it in the fridge, and now you can store your seeds like the pros! You can repeat the same process if you like to store ammo for long periods of time. I reload, so it’s nice to know that I can store my ammo in airtight containers at low humidity to prevent corrosion.






What else can we use this stuff for? Well, if you’re into home chemistry you can use it as a drying agent to dry acetone, toluene, or even ethanol.

Say, dried ethanol- that gives me a naughty idea!
Using another jar and some high-proof liquor such as Everclear (although lower proof liquor may also work- try it), place a minimal amount of your drying agent in the bottom and add in the booze. As it absorbs the water in the liquid your drying agent should begin to clump up/gel. Give the jar a swirl every now and then. When you’re satisfied, place a coffee filter in a funnel and strain the now more-potent ethanol into a container of your choice.



There is one complication though. I found if you use too much finely-powdered drying agent it will suck up the ethanol like a sponge and leave you with this:



Well, there you go. You’ve done chemistry and not only that; you now have a useful product in your hands. As you find new uses I would appreciate if you posted them in this thread. In the future keep an eye out for my other DIY threads. Enjoy!


Technical analysis/information:

MgSO4 = 120.3676 g/mol
MgSO4•7H2O = 246.47456 g/mol
H2O = 18.01528 g/mol
=48.8357% of mass of Epsom Salts is due to MgSO4
=51.1643% of mass of Epsom Salts is due to H2O

MgSO4•2H2O = Sanderite
MgSO4•H2O= Kieserite

Mass of Epsom salts = 592 grams
=2.40 moles of Epsom salt
Mass of pan = 497 gramsMass of pan + dried Epsom salts = 827 grams
Mass of dried Epsom salts = 330 grams
Expected mass of dried Epsom Salts (no H2O) = 289 grams
Expected mass of water lost = 303 grams
Actual mass of water lost = 262 grams
=41 grams of water remaining
=2.27 moles water remaining

Possible chemical composition = mix between MgSO4•H2O and MgSO4•2H2O

Originally Posted by smallclosetgrowr

so i was drying weed in a shoebox that would be ideal ?

You can 'quick dry' weed if you enclose it in a sealed container (not a shoe box) with some drying agent. Slow drying is the preferred method, though, from what I've read. But it can be used.

Originally Posted by catnips

love this subject (DIY home chemistry projects) : keep up the good work!

Thanks much! I hope this is a useful one .

Wonder if I can get an admin to sticky this. Any other comments/questions?

Edit: And then I realize there's already a DIY subforum. Doh.

An alternative is de-icer. I put it out in trays and in no time it is standing in water that it absobed. It may not work as well as epsom salt, but when you get it at walmart in 50lb bags it sure is cheaper! The active ingredient is calcium chloride so make sure it is a cacl based de-icer. Google calcium chloride dessicant for more info.

I should add that while it worked, when I had a humidity problem I found it easier to just buy a good dehumidifier. In bad cases you could use them together.