How to Store 3D Printing Filament – A Simple and Cheap Way to Keep Your Filament Dry
Did you know that some of your 3D prints may have partially or completely failed just because of humidity contained in the filament you used? This sort of humidity is invisible to the naked eye, so you probably blamed your print settings, your 3D printer or even doubted your abilities, but all of that may actually not have been the cause of your problem: it was the humid filament.
Some people tried to address this problem by creating more or less elaborate 3D filament storage solutions, like filament driers or special filament containers. The problem is that most are either bulky, energy consuming and/or slow, they come at a certain price or constructing them takes a lot of your time.
Well, we may have just the solution for you: a very simple and cheap way to store your filament without hassle. Your filament will not only stay completely dry, it will be easily accessible, perfectly identifiable (i.e. no need to open every box to find the right kind of filament your are looking for) and it uses humidity absorbents which can be reused indefinitely. If this has peeked your interest, read on.
Your failed 3D prints could well be due to humidity contained in your filament
If you have your filament spools simply lying around your printer until you use them, without any storage solution in place, you will sooner rather then later witness problems during printing, due to humidity. Your filament has an inherent quality that will make it attract water molecules its surroundings (i.e. the ambient air), known as “hygroscopy“.
As we already briefly explained in this article, nylons will saturate with water (i.e. absorb its maximal capacity in water molecules) in only 18 hours being exposed to ambient air. The situation is even worse with specialty filament like PVA (more about PVA in our materials primer post) which is used to create support structures, which are easily dissolved by putting your print in water. PVA is extremely hygroscopic and needs to be stored in a sealed box or a special container. Otherwise, it will attract so much water from the air that it will render it useless. But not only nylons or PVA are concerned, PLA and ABS also attract water from the air, even if it is to a lesser degree.
The effects of attracting water may result in one or more of the following problems: increased brittleness, diameter augmentation (potential problems with Bowden-tube printers), filament bubbling or hissing steam once reaching the hot-end, filament degradation, breaking filament, etc. which will all lead to increased complications during printing. You also need to factor in the fact that 3D printing filament which has absorbed water will need a higher temperature for extruding correctly.
The level of severity of these problems depends strongly on the type of filament. For instance, PET is nearly not affected by ambient air moisture while Nylon will saturate quite quickly and may pose problems printing (making bubbles for example), if not stored properly.
Not the best long term storage solution for 3D printer filament
The Maker community came up with some very innovative ways, in order to find a solution to this recurring problem. Some makers set out to build a filament dryer and storage containers like this “Moisture-free filament spool container“, this “Multiple Filament Dry Holder and Dispenser” or this “Solution for printing with water soluble PVA in Dualstrusion“, but you probably will have to go through different iterations in your designs, before you will be happy with your result. Also, there is always a certain cost involved.
Alternatively, you can check out the solutions elaborated by our good friend Jérémie François. He tried out several systems in his article on printing nylon (a recommended read) and his iteration of a high-tech zero carbon footprint drier box. Unfortunately, not everyone is living in beautiful southern France with accordingly good weather (i.e. lots of sun) in order to use such a drier box. Or you simply don’t want to tinker with such a (quite elaborate) setup.
The home-made solar dehydrator by Jérémie François
But don’t worry, we came up with a very simple, yet effective and very cheap solution.
Just get yourself some vacuum bags. Please do pay attention to only buy the type of bags fitted with a vacuum valve, which permit all air to be vacuumed out with a standard household vacuum cleaner. These vacuum bags are normally intended for storing clothes, linen and such in a place-efficient manner. They normally also provide protection against water, odors, mildew, dust and pests.
You need to be careful, as you can also find “vacuum bags” which are normally intended for traveling (i.e. storing clothes in a space-efficient manner in your suitcase). Those use integrated one-way air valves and need to be rolled manually (compressed) in order to let the air out. Sometimes you can find them tagged as compression bags. Pay attention not to buy those as they are not fit for our specific purpose!
Also, only buy vacuum bags with a double zipper line, as they permit to keep the vacuum better then the simple zipper lined ones. The better ones cost about 20 EUR (about 25 $) for 6 bags. One such pack will normally be more than sufficient for your filament storing needs. We strongly urge you to consider buying only the higher quality bags, as their valves are normally better, the plastics used are of higher quality (less prone to cracking over time) and thicker (less danger of a puncture).
Four filament spools and a moisture absorber packed together tightly in a vacuum bag
As for size, the choice is up to you, but in order to keep your stored filament manageable, we prefer bags of 50 x 60cm or so (i.e. 19.6 to 23.6 inches). Normally those bags are transparent, so you can easily recognize what filament you have stored in a specific bag. Clear and comprehensive tagging of your filament will also help a lot in that respect.
Pro tip: Once most of the air has been vacuumed out of the bags, you can easily and place-efficiently stack your spool bags or even store them vertically in a box or cupboard until you need them.
Simply vacuum out the air, so to remove all the ambient moisture too
The idea behind using those bags is to store your filament spools in an air-free environment (vacuum), so that they cannot absorb any more moisture from the ambient air. As the vacuum in the bag is not absolute, you need a solution to absorb any possible remaining moisture. We recommend to simply add to your bag some silicagel beads, which are very effective moisture absorbents. You can choose to either buy a number of ready-to-use silicagel packs (a.k.a. dry packs), which can be re-used if you dry them in an oven. However, their biggest disadvantage is that you have no way of knowing when the beads are saturated with water, as the (Tyvek) bags they come in are opaque/non-transparent. It is also sometimes difficult to buy them in small numbers at an acceptable price.
Once the air has been vacuumed out, you can conveniently store your filament spools completely dry until you need them
We actually prefer a much smarter solution, as we use silicagel with moisture saturation indicator. This amorphous, highly porous, synthetically manufactured silicagel uses an ecologically friendly color indicator, so that when the beads absorb moisture, they change their color from yellow/orange to green or blue (depending on ambient moisture level). The beads normally only become blue if they have been soaked in water (i.e. in contact with water) – we use the photos of the blue silica gel for illustration purposes only of this article. Your DIY moisture saturation indicator should only become green, never blue! Used together with some type of slotted box with transparent walls, you can easily determine if the time has come to renew your silica beads.
There are a few of these moisture indicator silicagel types out there. Beware and do not buy the cheap one’s which change from dark blue (dry) to pink (saturated), as they usually do contain cobalt chloride, a product which has been linked as being possibly carcinogenic to humans and has been labeled as hazardous material in some countries. We are no chemists, but apparently the color indicator in the orange to green changing silicagel beads is a kind of composite dyeing agent and a lot safer to use then the cobalt chloride one’s.
EDIT: “Since the publication of this article, we have received number of mails, asking us if you can replace the silicagel with rice instead. Rice is cheap and readily available and yes, it does present hygroscopic properties. But we advise against using rice as a desiccant, as its adsorption properties cannot be compared to those of industrially produced silicagel. If you compare rice to silicagel, you can say that rice is maybe a “mild/weak” desiccant. If you would like your filaments to be dried and stored under the most effective conditions, use silicagel.”
The only thing missing now is the appropriate container to put your silicagel beads in. Any transparent vessel with small holes, slots or incisions will do the trick. These are necessary so that the silicagel beads can attract the remaining moisture left in the vacuum bag. As seen before, some ready made solutions do exist, but those dry-packs seem to be only available in the US at the time of this writing. So, as true makers, we decided to 3D print us the vessel we need for our little project. You can use this design of a desiccant box which you can resize as needed and then 3D print it yourself.
Alternatively, get yourself some plastic containers with a screw lid, like those Polypropylene containers (slightly soft-walled) of 50ml which are frequently used by labs or for storage (coins, screws, etc.), which you can order on eBay or Amazon. Alternatively, search for small plastic jars with cap/lids or coin storage containers. To get a better idea of what I am talking about, just have a look at our photos below. Take out your drill (I used a 2mm drill for wood, as they are very sharp and perfectly suited for this) and add a good number of holes to the container, so that the beads can easily absorb any remaining moisture. Then you just need to fill in your beads and, voila, you have a moisture absorption system with water saturation indicator.
Once your beads change from orange to green(ish), depending on the moisture level (the vacuum bags and the bead container being transparent, it should be easy for you to check the saturation level), just take them out of your container, put them on a baking tray and let them dry for 3 hours at 120°C in your oven (some types may be also microwaveable, but we do not recommend this). Once they are of a clear orange color again, all moisture has been dried out of the beads and they are ready to be used again.
The 3 possible states of the silica gel: yellow (dry), green (wet, needs replacement) and blue (saturated with water). It will only become blue if submerged in water – you need to change your beads once they are greenish!
If your filament spools have already been exposed to the air over a certain time, they will most likely aready be saturated with moisture. If you wish not to change the silicagel too quickly or too often, you can try drying it in an oven first. But you need to be aware that this may create problems, especially if you are drying at too high temperatures, as the filament may become soft, sticky or may even start fusing single strands together in one big mess. Do not try to shorten the cure time with a higher temperature setting!
There are no specific recommendations we can give you here for “oven curing” your filament, as these settings depend on the nature of the thermoplastic you are trying to dry. As a rule of thumb, use a convection oven (i.e. a fan-assisted oven), where fans distribute the air evenly throughout the oven. Your heat settings should be low to very low. Just consider curing PLA, which has a so-called “glass transition temperature” of 60-65°C. This means that the PLA’s properties will change from “hard and brittle” to “soft, molten or rubber-like” as soon as your ovens temp reaches 60°C! So PLA is not really a good candidate for oven curing, unless you have a very precise (i.e. digital) oven. Also, we never cure our filament for longer than one hour, as the silicagel in the vacuum bag will take care of any remaining moisture.
Please make sure that you always check the glass transistion temperatures on your filaments, as they do vary widely: ABS is around 100°C, Taulman’s T-glase is around 78°C, Polycarbonate around 150°C and so on. Make sure that you research your filaments specifications properly before trying this out. And as usual, all the above is for information purposes only. Should you ruin your oven or loose a spool while trying to dry your filament, don’t blame us, as we warned you properly about this method’s inherent risks and dangers.
One last piece of advice: sometimes the filament, once you have finished printing with it and have pulled it out from the heat chamber (and Bowden-tube, if applicable), can form a spike or be kind of sharp. However, sharp spikes together with thin walled plastic bags do not mix well, as a vacuum bag is quickly pierced by a sharp tip. So we recommend to print some filament clips (many are to be found on Thingiverse), so that unraveling, entanglement and especially spikey ends do not pose any problems. Personally, we prefer this design.
Using a filament clip to keep the filament secured on the spool
We hope that this little instruction will help you keep your filament dry in the future. Happy printing!
EDIT: We have received a lot of fan-mail from our readers, requesting us to publish an easier method for storing 3D printing filament without involving any do-it-yourself action. So check out our new and revised method for filament storage that gets rid of any DIY-action and that can be implemented in a few, easy-to-follow steps by absolutely everyone
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