We’re so used to seeing a little sachet of desiccant drop out of a package when we open it, that we seldom consider these essential substances. But anyone who spends a while around 3D printing soon finds the need for drying their filament, and knowing a bit about the subject becomes of interest. It’s refreshing then to see [Big Clive] do a side-by-side test of a range of commonly available desiccants. Of silica gel, bentonite, easy-cook rice, zeolite, or felight, which is the best? He subjects them to exactly the same conditions over a couple of months, and weighs them to measure their efficiency in absorbing water.
The results are hardly surprising, in that silica gel wins by a country mile. Perhaps the interesting part comes in exploding the rice myth; while the rice does have some desiccant properties, it’s in fact not the best of the bunch despite being the folk remedy for an immersed mobile phone.
Meanwhile, this isn’t the first time we’ve looked at desiccants, in the past we’ve featured activated alumina.
One benefit for Team Rice is that it is relatively soft and unlikely to scratch up your phone if you just stick it in rice. Many other products will require proper protection of the phone or pouches for the desiccant, and for home gamers that could be on the net less effective than just sticking the phone in half a liter of rice.
Well, yes, but it doesn’t actually work.
A minor technical detail
Maybe a better desiccant?
https://www.wired.com/story/cutting-edge-technology-could-massively-reduce-the-amount-of-energy-used-for-air-conditioning/
i always used silica gel because otherwise you would just throw it out and that’s wasteful. rice is more useful as food. in ether case id also put the thing im trying in a hot box to speed up the process.
To be honest, the silica gell says do not eat on it, which really makes me want to eat it. My guess is it tastes just like chicken, but with a texture of tapioca.
While others my find this topic interesting I find it quite dry.
Good zeolite should out perform then silica as long as RH<40% (so called drying conditions).
The problem is it's too powerful that when you buy them, they already absorb 50% of useful capacity.
The required regen temp is 300+°C (450 preferred), much harsher than silica's 150.
Genuine question: i have a dishwasher which use zeolite in its drying air circuit. I doubt it can regen it at 300/450°C, so i wonder how it can possibly works?
I guess a lower regen temperature is simply compensated with a lot of zeolite since this stuff is cheap and a dishwasher needs a counterweight anyway to prevent it from tipping over when the door is open.
Going to ~150°C leave zeolite with maybe 30% capacity, so just pack more of it. However zeolite easily withstand thousands of regen cycle, which silica degrades
DO NOT EAT
“It was my birthday recently. For my birthday, I got a humidifier and a dehumidifier. I put ’em in the same room and let ’em fight it out. Then, I filled my humidifier with wax. Now, my room’s all shiny.”
– Steven Wright
Rice is the common folk remedy for wet electronics not because it’s particularly effective, but because it’s particularly **available**. Most folks don’t have large amounts of silica gel handy (although bentonite is commonly available as clumping kitty litter).
exactly this. I have people go crazy on me when they find out i use no scent kitty litter (that i verify is bentonite clay) as a desiccant, they refuse to believe it works. Been using it for a long time even before trying to keep filament dry….. good stuff and cheap. Plus you can dry it back out and reuse it.
What themperature do you heat it to regen it and allow it to be reused?
I normally weigh it and have a junk toaster oven i got at a thrift shop. put it in at 300 for about 1/2 hour then pull it out. It normally is pretty close to unused clay at that point. I’ve never done anything scientific with it just checking weight. I might be able to get better going longer or i might be able to quit sooner. Never really tried that hard to figure it out since it just works for me.
> put it in at 300
F, C, K or W?
@Matthias
Must be ℉ since toaster ovens don’t often go to 300℃ (and it would carbonise it?)
300 ℉ = 148.88 ℃
> must be °F
It is the most plausible, but the others would be easy to explain, too: in a toaster red glowing heating wires are not uncommon, which would indicate towards °C. Or K indicating that just slightly warming woud be sufficient (hot air rising above the toaster passing the cat litter drying it). Or W as in the power consumption, since old toasters tend to not having a real temperature regulation…
Calcium Chloride is an excellent dessicant and is cheap. Why are you guys using dessicant substitutes that cost more than real dessicant?
CaCl2 is fine for printer filament, but will cause corrosion in electronics/metals.
I’ve never had a problem. I guess it’s because I keep the calcium chloride in a separate tray inside a large box. The electronics doesn’t have to be in contact with the calcium chloride for it to work. Calcium chloride pulls the humidity of the air in the box to <40% which dries out nearby objects immediately.
Using CaCl2 in a car is a recipe for disaster.
Disappointed that calcium chloride is missing. It’s sold in hardware stores as humidity absorber…
Doesn’t calcium chloride need to be heated to 300C to convert it to the non-hydrate form?
Glad you should ask.
Calcium Chloride (CaCl2) reacts with two molecules of water (2H2O) and produces heat.
The resultant ‘brine’ contains Ca(OH)2 + 2HCl, that is Calcium Hydroxide and Hydrochloric Acid.
Yes its very effective, but not at all good for electronics, or in your gun safe either for that matter.
Safe? I keep my gun under my pillow! You never know when they’re coming for you, but they’ll probably try to get you when you’re sleeping.
I used to do that when I was younger, nearly blew the tooth fairy’s head off!
There is no significant amount of either calcium hydroxide or hydrochloric acid in the brine; it’s just solvated calcium ions and chloride ions. The equilibrium point of a mixture of Ca(OH)2 and HCl lies very far toward solvated Ca(2+) and Cl(-); the solution is probably (very) slightly acidic from calcium ions. Admittedly, those ions do promote rust/corrosion. [Source: the two chem textbooks I co-authored.]
Indicating silica gel is quite cheap and readily available. Look for “crystal cat litter” in the pet aisle. I drill lots of small holes in a plastic peanut-butter jar, fill it with litter, place it in the container with filament (or whatever needs to be kept dry). It’s cheap enough that it can be tossed instead of regenerating.
FWIW desiccants are good for *keeping* stuff dry, not so good for drying stuff that is damp. In organic chem lab, to dry a damp sample that couldn’t be heated (decomposition) we’d leave the sample in a desiccator for at least a week.
I’m more interested in knowing what is the lowest humidity one can achieve with each desiccant.
While the silica gel absorbs the most per gram, I’m betting that the bentonite cat litter is the most effective per dollar. It’s literally dirt cheap. :-) Also, it’s available in any supermarket. If you were making a large chamber to dry many reels of filament, bentonite might be the way to go (assuming you weren’t cramped for space). I think I’m going to try a freshly-opened box of bentonite cat litter to see whether it does need to be pre-dried, or if it comes from the factory dry enough. If the latter, it might even be cheap enough to throw it away rather than laboriously drying it back out (I’d probably just use it for its intended purpose as cat litter before throwing it out, getting essentially twice the bang for the buck).
Amazon is selling silica gel for around $4.50/pound. Generic cat litter at my local supermarket is less than $0.50/pound.
You can dry silica gel in a microwave. I doubt that works with bentonite.
Next week on project farm, lets see which mallet makes the biggest dent in big clives head for cutting into my action…
Meh. I just blow on things when I want to dry them.
I know it’s not the point of the article, but would it not be more effective to put a device under vaccum to draw out moisture quickly. The speed of drying is a huge factor since any device that still contains a power source is likely to experience copper erosion on the pc boards where moisture exists.. Spent more time that I’d like to admit repairing equipment that has been wet.
Anything with lcd tech might not enjoy high vacuum. Dont know if the barometers in a smart phone would survive prolongued vacuum.
I don’t know the actual limits although it’s probably available somewhere. But a mountain peak I was on was 0.59 atm, and even that is enough to aid significantly in evaporation. Especially as you can probably figure that the phone is fine for awhile while turned off at a somewhat warm temperature, and you can still use dessicant too if you’re not quite getting the evaporation rate you want.