Building a filament dry cupboard?

I live in a perpetually humid environment. It’s not even the beginning of the wet season and the temperature in my room is 27°c and humidity 79% in a week or two temps will be in 30’s and humidity mostly in the early to mid 80’s. It’s not the sort of climate where water condenses on things, but the timber floors and glass robe doors and mirrors do get decidedly sticky from the mix of salt in the air and claggy humidity.

I store my filament in ziplock bags with desiccant, inside not quite airtight Ikea plastic bins and there’s enough humidity in the filament and the bags to have to dry the filament every month or so, which I mostly don’t do unless there’s an obvious problem - then the filament goes in the food dehydrator for half a day and the problem goes away.

But I’ve been thinking…would one of those little half litre dehumidifiers work in a sealed cupboard? I don’t see why not and in Aus dollars they are about the same price as a commercial dry box that would fit one spool. I like the look of this one - it’s the cheapest I can find and it’s got automatical turn off, a yellow light and it comes on a fast ship (which is more than I can say for my dupont connectors). 500ML Portable Electric Mini Dehumidifier Air Dryer Home Office Drying Moisture | eBay

I’m sure it wouldn’t work at all in a room sized room, but I’m thinking an Ikea cupboard with a glass door, some cam latches and proper seals, and just let the thing run for a day after opening the cupboard or perhaps every week or so on a timer.

I’d appreciate any thoughts, particularly from anyone in the sort of climate where dehumidifiers are used regularly. I imagine there is a flaw in my thought process somewhere or it would have been done before?

Thanks in advance!


I’m using a big ziplock storage box with rechargeable dessicant in it.

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I have been eyeing these,, or at my last job we were going to try a gun safe dehumidifier in the large cupboard we stored filament in The second one probably won’t help much though in a sealed box.

That first one is what I have in my box. Well, two of them. They came in 2 packs at sam’s club a couple years ago. The heaters won’t do anything unless there’s a way to get the water out. All they’re really meant for is to keep the guns in a safe from condensing the water out of the air if they get cold.

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[quote=“vicious1, post:3, topic:29817”]
I have been eyeing these,
[/quote]I have a similar gadget and it works very well in a small volume, like this box IKEA 365+ Food container with lid, rectangular, plastic - Buy online or in-store - IKEA which I use to keep my camera gear in. Just take it out to recharge every month or so and it’s really convenient- but haven’t had the same luck with the filament boxes - it all gets a bit fiddly.

All of which is why I wondered if one of those water extracting types would work - seal the cupboard, run it till the humidity reaches an acceptable level and turn it off?

BTW @barry99705 I’d be delighted to keep my filament at 52% (IN the box!)

Now you have me intrigued - I’m going to weigh stuff and report back! :smiley:

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This is an intriguing idea. I know that those dehumidifiers work on the concept of condensation to extract the humidity from the air. It runs a small AC air conditioning pump internationally. Runs air across cold fins that collect the moisture. Then it runs the air through the heating coils so it comes out of the machine close to room temperature. The moisture is collected in a water tank or drained through a tube.

I have one unit that brings the humidity in my entire house from about 75% down to 40%. So cubic footage is not a huge concern as this little guy claims to be able to work in 4,000 square foot buildings.

So a small unit inside of a cabinet is intriguing. It should work as it would circulate that air and turn on and off automatically. If you have a drain tube then you don’t need to worry about emptying the tank.

It should work. Fascinating idea.

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I saw these at the big orange church a week ago. They should work too.

We’re in Florida now, so the ac runs all the time. My room faces the sun in the afternoon, so it gets warmer than the rest of the apartment. The filament box has tapered off to about 24%, and it has a bowden tube coming out to my printer.


The comparisons are interesting and I’m not going to draw any sensible conclusions from them except that I’d rather be using your filament than mine! Compared to Miami Fl we apparently average 2°c lower temperatures over the year and 6.5% higher humidity. The patterns are so different though that’s probably where the comparison should end - for instance your average humidity apparently fluctuates madly during the day from high in the morning to quite low in the evening - ours just sits on 75% more or less all day every day (except that as I write this we are having a monstrous weather system from the inland with 35°c (95f) and 20% - almost an all time low! (Don’t forget our seasons are the reverse of yours which also makes direct comparisons difficult)

We don’t bother turning the AC on until it’s about 32 (it’s not on today for instance) so in the humidity fight we are our own worst enemies! :smiley: We usually have it set between about 24 and 26 to keep the condensation on the windows to a minimum! :rofl: :rofl:


I’ve just weighed my half-roll of PLA in the food dehydrator and the dessicant canisters - after three hours at 50° the 90g silica gel is down 4gms and the PLA more than 10, so that’s 14mm of water so far, and apart from when they are in use they are kept sealed in a ziplock bag.

I was only going to run the dehydrator for six hours but I might let it go for eight before the next update.

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Well I’m seriously hoping my bits will arrive today so I can get on with the LowRider and a couple of other projects, but in the meantime I’m lost in the humidity rabbit hole.

I now know for instance that our cheap hygrometers measure “relative” humidity. And that as the temperatures go up the amount of water in the air increases markedly for the same “relative” humidity. Therefore storing filament at 70% humidity and 30°, is a bit like dunking it in a bucket of water at 20°!


I’ve also learned that the silica gel cassettes i use actually do quite a lot of good. At the moment I store my spools in ziplock bags with a canister containging around 80gms of silica gel.

It takes 12 hours in a food dehyrdrator to regenerate the canisters, and after measuring six of them this morning - each has lost an average of 10 grams, or 10ml of water. Given that the bags have little air in them this is astonishing to me, however the two spools I dried for the same period lost barely 1gram, so I can assume that the desiccant really is doing what it is supposed to do and I really shouldn’t fret.

It’s just a pain to remember to pack each spool after every use, and to have to methodically open a dozen or so packets every month or so to go through the drying process. Did I mention that these packs are in turn kept in a box like @barry99705 's(although with no desiccant in the box).

I’m not sure where i’m going with this, but don’t be surprised to see a new Ikea bookshelf arrive in this thread in a week or three, and since a cheap dehumidifier will cost no more than half a kilo of silica gel…

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This is cool info. Thank you.

Now maybe someone in this group could help test a related theory I have been rolling with. I don’t have the means to test it myself or I would. Here it goes. When the air is warm clouds float. This is seen in small sealed containers as well when the warm water vapors collect at the top of the container then drip back down. Meaning we might be better off putting our desiccant at the top of our containers rather than the bottom. Or in other words should the desiccant be placed above the filament or does it matter? I have been attaching my desiccant to the inside of the lids of my bins. Is this helping?

Soooo if someone has the ability to test this theory it would be super cool. I have a simple idea for a test. Sealed cereal container with fresh desiccant at top and bottom. Weigh the desiccant before. Add moisture into the container. Could be done many ways but adding a slice of bread that is held in the center would be good. On a small shelf. Or a cup. Wait a couple days. Then weigh the desiccants. The test could be performed with different room temperatures but room temp was the main idea.

I don’t have a scale or access to my dehydrator.

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At any temperature, water is heavier than air.

The reason that you get condensation on the top is that the top is where most of the heat escapes from inside, meaning that the top surface is the coolest, therefore the highest relative humidity, and the first place to reach dewpoint.

Also, clouds appear to float because warm humid air rising cools until it reaches the dewpoint (6.5°C for every 1000m altitude) when that water condenses on whatever bit of dust it can find.

This is a different phenomenon from the mirror in the bathroom while you have a shower. That mirror will generally fog up closest to the top because the air in your bathroom is not at uniform humidity. The humid air from the shower is warmer than the rest of the air in the bathroom, so it rises to the top of the room. Not because it is humid, but because it is warmed by the hot water of your shower. When the heat comes on next, the mirror will defog by itself closest to the top. The humidity in the room is more uniform with the addition of the new warm, drier air, and the warm air near the top might carry the same amount of water, but will have a lower relative humidity, because it is warmer.

Probably the silica gel is best off near the bottom of the container. When the humidity is uniform in the container, and the temperature is reasonably at equilibrium, not getting warmer or cooler, the coolest air will settle to the bottom, and have the highest relative humidity, which will have the greatest tendency to lose that water to the silica gel.


It’s also important to note that humidity is very pervasive. Meaning the amount of water in the air inside a closed space will almost always be the same regardless of where you sample the air. Only the relative humidity changes with air temp. So where a desiccant is placed would make very little difference, it’s more important to make sure you get good airflow around the desiccant than anything else. At least that’s what I learned when I was doing hvac and trying to get it so meat packing plants would stop having rain indoors :laughing:


My guess is that the humidity is pretty constant in the whole container (it’s a box, pretty small for a speeding air/water molecule). Given the time scale, I am not sure air flow is that important either. It probably reaches equilibrium much faster than a meat packing plant and the source of moisture is much slower (you open the box a few times a day at most and it adds some moister air). The desiccant should remove moisture from that new air faster than the plastic and then over longer periods of being closed, the plastic will probably release some more moisture.

Very interesting ideas though and there are good ways to test it.

Personally, I have resigned to pretty much go through plastic completely when I open it. I don’t do color swaps and if I need a specific color, I try to make that the next one I open. Sometimes I print a bunch of boxes to get rid of a color. So I’m not much help.


That worked for me for a while. I use both PETG and PLA in pretty much equal amounts, and I tend to use the “left overs” for templates and test fits, but somehow I’ve got eight or ten or eleven open rolls! :open_mouth: I didn’t think I did colour either and certainly can’t see any need for a multi colour setup.

On the other hand, I’m presently working on a monster project - a pair of ear-rings for a granddaughter - it uses a total of 0.1 metres of filament ( 0.3grams) and has THREE colour changes! I think any hope for me is lost.

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Heck, I think I have a half dozen or so open rolls of PLA that have been sitting out for literally years. I wonder if I should cobble up a dehumidifier for a while and try printing again. :slight_smile:

A cheap food dehydrator (mine was very second hand) will quickly rejuvenate old PLA - I’ve thought about just leaving a roll in the car on a sunny day - if you keep it out of direct sunlight that might keep it warm enough for long enough - depending on where you live of course.

Just thought I’d demonstrate the depth of my problem! It’s heading for a very mild 27 top today, but that’ll still feel a bit unpleasant - like living in a warm shower really. Most of the el-cheapo RH gauges give up at 90 and just read “HIGH”. This is why it’s difficult to stop things rusting too! :smiley:

Don’t listen to me. I do not have humidity problems.

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I don’t know, the TV room is getting up there! Now if I could store my filament in your house… (my dry boxes don’t even get down there!) :smiley:

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A small update. I have moved all my filament into Ikea 365+ boxes and with 160grams (a sort of random amount) of desiccant in each, “wet” filament stores in the high 20’s RH at 27°C - which is way more than many people think is extreme - but the filament seems to print well at that.

I stumbled across this video today though - and my thinking juices are running again.

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