You could test your theory by measuring the weight of the desiccant to track exactly how much water it absorbs in a sealed bag over time. If the weight never changes, then no measurable moisture is getting into the bag.
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Just a note on containers & their lid securing mechanism. When selecting a container to hold your spool, take care to select one with a “proper hinge”. I purchased a number of 5 L Sistema containers because they have a proper hinge mechanism to secure the lid:
Contrast that to many containers which rely on thin plastic bending to serve as a hinge, such as this:
The repeated bending of this thin plastic will result in failure over time. Once that plastic rips, the hinging mechanism is kaput and so is your seal.
The Sistema containers work well for me, but they are significantly larger than a single spool but are not large enough to hold 2 spools, thus they are space hogs. They are also on the pricey side and often difficult to find. The cereal containers and others with bending-plastic “hinges” are generally more abundant & less expensive, but they will wear out faster over time.
I use not only the Sistema 5L containers, but I also have several of the less expensive cereal containers and vacuum seal bags. The vacuum bags I use are from Sunlu because they have a treaded valve to connect the pump to and are thus easier to use and their seal seems to be quite good. A few desiccant packets in each bag or box work well for me in Charlotte NC USA.
As an aside, I got quite a good laugh at one fellow in a community discussion group elsewhere who was one of those self-proclaimed experts on everything. He lives in the desert southwest USA & declared that discussion of moisture & filaments was overblown because he didn’t use desiccant & never had a problem with moisture. Of course he didn’t - he lives in a desert!!!
Point is, it is up to each of us to decide what we need for our local environment. I find these community discussions excellent for challenging our views and teaching us the lessons learned by others.
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Regarding the topic of whether molecular sieves perform better than silica gel, I think maybe this demonstration answers the question:
My remaining question: what could be done to speed it up so that it takes less than 48 hours? Increased air flow? Heating it up? Anything else? Maybe even just more of it alone would speed it up by a lot? So much is left unanswered.
I too ordered a couple to try. They were running a two-for-one sale at the time:
Not sure how often that kind of sale comes up, but if you’re ordering a lot, it might be worth watching for.
I view the extra space as a bonus: more volume to fill with desiccant. 
As for the cereal containers: maybe someone will design some 3D printable thumbscrews for the corners to help latch it down, and then post them somewhere? As it stands, I would agree that the seal looks to be rather iffy. Maybe augmenting thumbscrews with a full-on pressure plate is what’s needed to really crank it down well.
Thanks for sharing the YouTube video. I clicked on it expecting to be greeted by a commercial. When the voiceover started, it used a well-known voice actor famous for doing documentaries. I can’t place the name right now, but anyone who is a big fan of the old Learning Channel and Discovery before they turned to reality TV will know what I mean.
Did anyone notice that this was junk science? My college Laboratory Science 101 Professor would be rolling over in his grave right now. Let’s pick it apart.
______________________________________________________________
- They show as their experiment a batch of blue color-changing silica gel which they expose to moisture over time.
- They weigh the sample to show that they are using “scientific” method. OK, so far so good.
Here’s where the wheels fall off the wagon.
- They take the new molecular sieve packets and place them in a sealed jar with the moisture-laden silica gel. Within 48 hours, they show that the packets absorb the remaining moisture that the silica gel had absorbed.
Duh!!! That proves nothing!!!
______________________________________________________________
While I’m not saying that molecular sieve may not be effective, the commercial is misleading to the point of being a grift. Elizabeth Holmes would have been proud. 
This is how people get duped. One might think the experiment is credible due to the laboratory setting, yet they commit basic errors against valid scientific methods. It incorrectly leads one to think their product is superior when the experiment proves nothing and only serves to discredit silica gel.
Q) What’s missing?
A) They did not run the experiments comparing how the sample might have reacted with an equal amount of unexposed silica gel.
Would Silica Gel have performed as well? We can’t know because they didn’t run that test did they? It might have changed the viewer’s conclusion if it had shown that an equal amount of silica gel also absorbed the moisture. If they had placed the same amount of unexposed silica gel in the container, it would have likely turned a neutral color between unexposed blue and exposed pink, absorbing half of the moisture after reaching equilibrium.
Here’s how a scientist might have conducted the same experiment:
Summary
-
Establish 4 containers of silica gel.
- Container 1 remains sealed as the control sample, isolated from environmental stimuli while the other 3 are the experiments.
- Samples 2-4 are exposed using the method shown.
- Sample 2 is placed back in a sealed jar without external stimuli, representing the after-exposure sample with no remedy. This ensures no other external stimuli affect the exposed sample.
- Sample 3 is placed in a sealed jar with the molecular sieve.
- Sample 4 is placed in a jar with another sample of the same amount of unexposed (blue) silica gel.
-
After allowing the four samples to sit for 48 hours, a true scientific comparison can be made between them.
This revised methodology follows accepted scientific methods by:
- Ensuring a proper control group (Container 1) to isolate the variable being tested.
- Using multiple test groups (Samples 2-4) to evaluate the effects of different treatments.
- Providing conditions to compare the performance of the molecular sieve against the silica gel accurately.
- Controlling for external factors to ensure valid results.
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Wow!!! $9.99 each is really cheap!!! (Green with envy here!) The thing with Sistema on Amazon, at least, is that the prices vary dramatically, especially given Amazon’s dynamic pricing. Anyone who is interested in these should monitor the price for at least a few weeks to get an idea of what a good price is.
I don’t think that the cereal containers have, generally speaking, poor seals if they are made correctly. The main issue I see is that the plastic that bends when you snap them shut/open them up will eventually tear & once that happens, the seal is compromised. I suspect that the Sistema contains will last far longer.
I don’t think there is any realistic repair for those plastic-bending latch systems once they tear off. If the latch is not torn but won’t stay down over the lip because the plastic has worn too much, a thumbscrew or some other fix may work. But once the plastic tears along that bend crease, its shot & the seal is compromised. If you are familiar with Snapware kitchen containers, if one of the 4 latches tears off AND the base is glass, it will still maintain a seal with only 3 sides latched. If the base is plastic, it usually won’t maintain a seal. The cereal containers are like the Snapware containers that are all plastic.
Another consideration is your storage space configuration. I have an Ikea shelving unit with 16 cubicles, each 13.25" x 13.25" x 13.25". Each cubicle will store 4 Sistema containers stacked 2 high and 2 deep. But the cereal containers I got are too tall to store in a cubicle.
NeverDie Thanks for the lead on this. I just ordered another 4. The $9.99 price can’t be beat - last time I purchased these, I paid $15.61 each.
Someone else was asking about cereal containers. I purchased a set of these:
but haven’t received them yet. They are a bit small in height so they should fit in my Ikea cubicles. The line is here: Amazon.com: YASHE Cereal Storage Containers Set 4PCS (3.7L/125oz), Airtight Plastic Food Containers with Lids, BPA Free Food Storage Containers for Kitchen Pantry Organization, with 16 Labels & 1 Marker: Home & Kitchen
They are literally half the price of the Sistema on sale so they may be more affordable for some folks.
Again, many thanks NeverDie for the info on the Sistema sale - greatly appreciated!!!
Ideally I’d prefer an all-metal military ammo box, because then it would be cheap (because of mass production) and built to a demanding military spec. Plus, moisture won’t ingress through metal, so probably better for long-term storage. Maybe they exist, but to date my search has only found ones that are too short in height to serve the purpose. Very frustrating! If anyone reading this has found a suitable one, please post a link.
So far, the closest viable one I’ve found is the 25mm pa-125 ammo can, which has larger than needed dimensions, but at least it would be viable, unlike the many shorter ammo cans that can’t fit a spool. For these, price seems to knock them out of consideration. I guess they aren’t in the sweet spot of mass production.
I like this guy’s design;
because:
- filament rewind capability without having to open the dry box; and
- ample space to fill with tons of desiccant
In contrast, I tried the cereal box design, but it seems to gain about 0.1g of moisture weight per day. That may not be much in the short-term, but wihout an adequate desiccant buffer, then over the long-term that moisture will be re-attaching to the filament.
This isn’t exactly what you’re looking for but this is what I use. They are plastic but they have a rubber gasket sealing them. I can fit 5 spools in here with a ton of desiccant. $20 each so not cheap but not crazy expensive either.
https://www.amazon.com/gp/product/B01CNP4HOY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
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I like this guy’s videos. He was the one who showed me that one could make a dryer using the filament cardboard and the build plate.
Although I love his work, the plastic container he cited when I found it was huge and expensive. More than the price of a spool so I quickly skipped it. Since I posted this thread, I have stumbled across cereal boxes on a Prime deal where I was able to pick up 6 at $3.75. I’m glad I didn’t spend full price because that solution simply is inelegant to say the least. First, one has to print a bearing supported roller. That adds another $3.00. Then one has to note that that cardboard filaments don’t properly fit in the cereal box I had. oddly enough, this was the same box that many on Printables were recommending but it really is only suitable for either storage or if you wish to use it as a spool feeder drybox, it will really only accommodate a plastic Non-Bambu reel.
This is the one I purchased that’s too small.
Here’s what I paid which worked out to $3.75 each.
In my view, the the Ezy Storage box from Home Depot that @lexi turned us onto earlier in the thread made the most sense on a cost per spool/space per spool basis. The cereal boxes simply don’t stack as well and certainly don’t pack as densely on the shelf. But I am glad I at least figured it out for myself.
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I personally just put them in a large plastic bag with dessicant beads in a permeable bag and a humidity sensor. It keeps it around 10% for me!
@Olias Yes, those Praki (and some others of the exact same design but with different names) are a popular choice. They’re somewhat limited though as to how much desiccant you can pack into them. Maybe it’s fine if storage is the only goal, rather than storage plus filament feeding into the printer. I haven’t found any designs featuring a rewind knob for it. Also, from weight measurements, moisture seems to find its way in at the rate of about 0.1g per day. And that’s on brand new ones, not old floppy ones. YMMV. So, I’d consider adding further moisture intrusion barrier (another dry enclosure perhaps?) around it to maybe slow that down for a deep storage scenario.
That said, I agree that the systemi box is overpriced for what it is. I’ve found equivalent size boxes for a lower price (around $6 each), but then the rewind mechanism would need to be revised to fit it. I could do it, but it’s yet another diversion that I’d rather not take on. No free lunch I’m afraid. I have a hunch I’m going to end up with one set of boxes for deep storage and another set of a different type for use while actively feeding the printer (when not using the AMS).
The rewind box itself isn’t perfect. I’d rather that it have o-rings to further prevent any amount of moisture intrusion through the drilled holes. So, even though I like it for the extra desiccant capacity and the rewinder, I wouldn’t call it perfect. But what’s better?
This dry-box is interesting because it includes a scale, so you know how much filament is left:
https://www.aliexpress.us/item/2255800656323022.html?channel=twinner
Doesn’t look as though it would have uniform heating though.
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WOW!!! That is one vastly over-engineered and, I might add, over-priced solution. I’m shocked the Chinese would even attempt something like this, so I have to believe that this is a product someone contracted a Chinese company to make for another purpose and some entrepreneurial individual adapted it to filament drying. This looks very reminiscent of a .50 caliber Mil-Spec ammo box. Harbor freight has them for under $20. Hmmm… maybe 
this just might be a cool project to work on. Adapt a harbor freight ammo can to a drier. 
Their also all over eBay.
https://www.ebay.com/b/50-Cal-Ammo-Can/165616/bn_55186809
I dry the filament until it stops losing weight, then use a vacuum sealer to seal it up along with a 50 g color changing silica packet. When the silica in the packet changes color, I microwave it at 30% power for 4 minutes, turn it over and microwave (30%) for 4 minutes, turn it over again an microwave (30%) for 2 minutes, maybe 4 if I have a few packets.
Occasionally, after repeatedly opening and resealing the vacuum seal bag, it fails and doesn’t hold a vacuum seal anymore, but it’s a slow leak so not noticed until later. When that happens I used to just change the bag, but now I reheat the filament and recharge the desiccant because it absorbs more moisture than I expected.
My silica packets are orange and turn blue when they need to be recharged. Originally I held the packet up so light would shine through and it looked orange so I continued to use it, but one day when I had a new and old packet lying on a table, the new packet was bright orange and the old one was kind of dark (didn’t look blue), but still looked orange when I held it up to a light. So make sure to compare the difference between a new and old packet while on a table so in the future you recognize when it needs to recharged.
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@Olias The harbor freight ammo cans aren’t tall enough, but the “tall” version 50 cal cans you linked to on ebay would do it.
I do kinda like the all metal “flame proof” aspect of it. You could heat your filament hella-hot without worrying that some plastic enclosure around it would melt. I assume that’s what’s holding back a lot of the consumer grade filament dryers.
Wanhao appears to be a knock-off 3d printer brand that makes extra-tuff stuff (a rhino is their mascot logo). I never heard of it before either, but they have a whole line-up on aliexpress.
Some stuff I’ve learned in my travels… Deserts aren’t always dry. I live in one and we’re in monsoon season with rain all the time this time of year. About two months of it.
About molecular sieves - they grab water like crazy but because of that they take really high temperatures to regenerate. Similar for Drierite/gypsum/calcium sulphate. Very effective but energy intensive and a pain, but if you need to “finish” air and get it really dry, those tend to be the way.
In my test dryer setup the ambient air is piped to the bottom of a container of silica gel. I ran the air dryer for over 6 hours yesterday in 46% RH ambient air and the silica gel got hit first. It picked up 3.84g of water in that time and the infrared images I took still had the heat of adsoption/condensation confined to about the bottom inch of the container according to the IR image. There has been no visible change in the indicator color yet. Air flow was low but it shows the water grabbing is actually pretty fast or the band would be taller.
Blue indicating silica gel is hazardous. Use the orange.
The cheap hygrometers/thermometers are actually surprisingly good. I’ve had great agreement over the ones I’ve bought. Can’t comment on accuracy, but for tossing in with filament, ballpark is fine.
To me all this adds up to silica gel being fine for drying/maintaining filament as long as it is kept dry itself. I’m really liking the container approach with a silica gel packet and a hygrometer and also appreciate all these recommendations.
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Good advice. The indicator color migrates into the desiccant over time and the color weakens.
How does it show in the IR image? When it picks up moisture, does the desiccant release heat (or cool down) or something enough that your thermal camera picks it up?
I’m just today trying this (pricey) filament dry box:
I’m able to fit 400g of dry-and-dry silica gel desiccant into it (4x100g sachets). It has a promising gasket to provide a hopefully airtight seal around it while closed up. I very much like the spool handling mechanism. Its on bearings and a spool of filament moves very easily. Maybe a little too easily? It has what seems like some felt on 3 sides of it to perhaps provide some resistance. Not much, but not zero.
Limitations:
- Can’t see inside as to how much filament is remaining. So, I’ll need to either keep track through the slicer estimates or else weigh it and then do subtraction to get a handle on that. If I felt adventurous, I could maybe ESP32 something with an ESP32 camera and some LED’s to light-up the inside when I wanted to see. It’s so cheap now, so why not? Best of all, though, would be using a filament gauge to actually measure how much filament has passed out of it. Not difficult, per se, but I haven’t gotten around to that yet.
- No external rewind feature. If I need to rewind, I have to open the case up. Maybe this could be overcome with some strong rare earth magnets? Maybe, but not something contemplated in the official design.
I purchased it a few months ago and am just now getting around to trying it out. I suppose what made it interesting is, in part, that the company sells high end commercial grade printers, and it is seemingly what they use internally as well as sell to their commercial clients. Also–I hope this doesn’t sound too jaded–being an american company, maybe there will be some of that good old fashioned american quality like back in the day. Maybe for such a simple thing it doesn’t matter, but, meh, worth a try. Who knows? Just a vague hope that an actual engineer might have been involved in its design: if nothing else, maybe the choice of plastic is less prone to moisture penetration or something.
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