Can 3D printer filament go bad? Causes and their solutions!

More often than not, we can be relatively confident that our 3D printer is well calibrated and ready to print incredibly good looking object at our high quality standards. Suddenly, we decide to print a new object with a spool of filament that has not been used in a while. To our surpise, we notice that the outcome is well below our usual expectaitions.

So, can a spool of filament go bad and loose its properties? What are the most probable causes of this problem?

A spool of filament that has been improperly stored can lose its desired properties because of multiple causes. If the filament is not stored in a sealed package with silica gel, it will be prone to absorb moisture. Exposure to UV light during prolonged times can turn the filament brittle and prone to breaking. The spool can also get tangled if not properly secured to the holes of the spool before storing it.

In summary, here is a table of causes that can render a spool unusable, its consequences and its solutions.

CauseWorst FilamentBest FilamentConsequencesSolution
Exposure to UV lightPLA
Filament gets brittle and prone to breakNo solution
Exposure to moisturePLA
– Poor adhesion to build plate
– Bubbles in nozzle
– Heterogeneous results
– Start and finish of extrusion get delayed
– Nozzle stops extruding
Dry in oven at 40°C for 3 hours
Use a blower dryer
User an Air Purifier
Tanglement in spool– Affects all– Affects all– Nozzle stops extruding filament– Always secure the tip of filament in the spool holes after usage.
Spool holder friction– Affects all– Affects all– Nozzle stops extruding filamentPlace spool on objects that are less prone to generate friction.

How long does filament generally last?

If the filament is stored in a dry and relatively cool place and kept in its packaging to prevent moisture, you can expect your filament to keep its properties for at least 2 years. This holds true for most popular thermoplastics, like PLA, ABS, and PETG. The exception to the rule is Nylon, which should be avoided after 12 months of shelf life.

Keep in mind that the filament’s printing quality much longer than 2 years, but you will need to use it in order to find out. This means that you should avoid at all costs to buy or sell spools that have been aged for longer.

Regardless, there are too many variables involved with the filament, so it’s almost impossible to know definitively how long any given spool of filament will last with your printer. 

The lifespan of a 3D printer’s printing filament depends on a lot of factors, like the filament’s local atmospheric conditions, its exposure to sunlight, temperature, and humidity), and the initial quality and type of the thermoplastic.


Typically, PLA Filament has a shelf life of about 2-3 years. This means you can buy it, store it in a cool, dry place in its original packaging (to prevent moisture), and still be able to print with it almost 3 years later. Keep in mind that after 2 years the print quality may gradually degrade.

PLA filament can last a long time before it begins to get brittle and show signs of wear, but certainly avoid PLA spools that have been stored in a hot garage or out in the sun. PLA doesn’t like heat or being exposed to UV. On the other hand, PLA stored indoors at room temperature can last for years without a decline in quality.

Once I came across a PLA filament at my workplace. This particular filament was new but my colleague had left it in the direct sunlight for a couple of weeks. He had assumed that there was no need to store it properly as we usually consumed a 1 KG spool within a week, and we never had any issues, but this time, he placed it near the window where it was exposed to direct sunlight during hours every day. We were shocked to see that it had become so brittle that it snapped like pasta. Lesson learned!


An ABS filament has a similar shelf life to that of PLA, meaning that, if not exposed to moisture, it can last up to two years outside of its package. 

ABS is a stronger and more durable material than PLA. Because it hs a higher glass transition temperature (105°C compared to the 60°C of PLA), it can better withstand the heat.

Although it is less prone to water absorption than other thermoplastics, it is still a good idea to be on the safe side and keep your ABS spools in friendly environment. By this we mean to keep it inside its packaging with multiple silica gel bags.


Nylon’s great affinity for water is problematic, it absorbs water like a sponge, which causes it to swell and bind up the printer nozzle. This can create inconsistent outputs, especially when using an extrusion printing process.

Nylon filament can absorb moisture from the air. In only a few days, it can absorb between 1% and 3%. This high water content will cause the material to fail when printed.

In technical terms, Nylon is a thermoplastic that fits has the property of being hydrophilic. It is a fancy way of saying that it loves to absorb moisture. Of course, we 3D printing enthusiasts do not love this property so much.

For this reason, if Nylon is left in the open, its lifespan reduces significantly in a matter of only a couple of days. It is also unsuitable for printing products that are meant for outdoor uses. Most Nylon brands have a maximum shelf life of 12 months.


PETG is a co-polyester, it has two main components: PET and glycol. It is stronger and more durable than PLA; PETG filament has a higher glass transition temperature which means it doesn’t warp or bend under heat. It is also more flexible than most other filaments, and not as prone to cracking.

Store PETG filament in an airtight container, to keep it away from moisture. Storage temperature is also critical. PETG filament can last a long time if it is stored in a cool place, but if the filament is exposed to heat, it will become brittle and crack, especially when simultaneously exposed to moisture.

Most PETG filaments can be stored for 2 years or more before it becomes brittle and cracks. You should keep it in a cool place and away from moisture or direct sunlight to make sure it retains its qualities as long as possible.

How to tell if a filament has gone bad and what causes it?

The bad news is that there’s no clear way to tell if a filament spool has gone bad. The good news is that 3D printers will not be damaged in any way by using old filament, so you can always try and print a test quick test object to check the overall quality of a spool.

Sadly, most people don’t discover that their filament has gone bad until it has already ruined an entire print job – or worse.

There are also a few ways to manually check the current state of your filaments. The filament that has gone bad will have no spring back to it when you try to bend and stretch the filament. The material will feel brittle and snap under pressure. There may also be an off smell to the PLA as well. If you start noticing a change in color, texture, or smell in your filament, it may very well be a sign that your spool has lost its properties.

People recommend the following three tests to identify a bad filament: 

  • Stretch test: It’s not a fully reliable method since PLA can be a bit more flexible before breaking down. This method also requires that you have a bit of faith in your own powers of observation under magnification. I consider this to be a waste of time since it does not yield conclusive evidence.
  • Stress test: An even less reliable way to examine PLA filament for signs of degradation is to leave it hanging vertically for some time before testing. Also do not recommend it.
  • Print a small object: this is by far the best way to test the current quality of a spool of filament. Print a small object with your usual settings and check if the output is as good as you would expect. If you hear popping noises during the extrusion, you can be certain that you are dealing with moist filament.

As you may have noticed, I’m clearly not a huge fan of the first two recommendations that are usually tossed around. Why would you perform tests that give you a hint of the quality if you have a quick and easy way to test the very thing you are trying to measure!

How does moisture affect filament?

Same object printed with a well preserved filament (left) and a moist filament (right). Source

Moisture accumulated in a spool can lead to very low-quality prints and even breakage. If your filament is coming off your spool stretched out and stringing, it could be an indication that your filament is not sufficiently dry.

The consequences of printing with wet filaments are numerous, and it is one of the main causes when obtaining bad results.

Just read through the list of possible consequences of wet filaments. You certainly would like to avoid this!

Wet filament may lead to:

  • Finding holes on the top layers of your parts
  • Bubbles on the tip of the extruder
  • Poor adhesion to the buildplate
  • Very heterogeneous outcomes when printing the same model
  • Start and finish of extrusion is delayed, leading to poor quality
  • Nozzle randomly stops extruding filament

Why does moisture have such a big effect on printing quality?  What exactly happens?

As you already know, 3D printer filaments are made from all kinds of fibers, copolymers, and other components. These are affected by local atmospheric conditions like exposure to sunlight, temperature, and humidity. 


The foaming phenomenon is the main reason for filament expansion. It is bad for your prints. It makes the layers weaker and can make the print look like a slice of Swiss cheese. It is caused by two factors: evaporation of absorbed moisture, and excessive retraction.

Foaming is the process by which the polymer molecule is broken down into a gaseous state. Polymer molecules are large and can unravel easily. As a result, they lose strength when wet and can even break into separate sections. The energy required to disrupt these bonds makes the filament swell up and expand. 


Hydrolysis is another process that happens at an atomic level: As the polymer soaks up water, it degrades by breaking some of its chemical bonds. This turns the polymer into a monomer. 

When you’re using your 3D printer, a filament with low moisture content is very important. Blown bubbles in the print turn even the most beautiful design into a jumbled mess. Proper filament drying ensures that your designs come out clean and beautiful. We want to ensure that you have access to the best tools at the best price so we guarantee that our filament is properly dried and bubble-free.

How to fix filament that has absorbed humidity?

Probably the simplest, most cost-effective way to gradually equalize humidity across a filament is to desiccate it using some kind of oven.

A regular kitchen oven is the simplest and the fastest way of drying filament spools. Heat can evaporate a lot of water from the filament, which will help you get rid of excess moisture and make your 3D printing experience trouble-free again. 

Kitchen ovens will do a good job, before using them, however, you must consider that they are not designed to heat filaments, so you must be extremely careful not to overheat them and definitely set the temperature below the glass transition temperature.

In order to properly dry a wet spool of filament, set the oven at 40°C (104°F) and leave it there for about 3 hours. Every now and then check how the process is coming along, especially for making sure that the temperature is in the desired range.

Remember that the glass transition temperature, the temperature at which PLA starts to become malleable, is only 60°C (140°F). If your oven reaches exceeds that temperature just for a few minutes, you can be certain that the spool is ruined for good.

This process is prone to generete fumes, so it is a best practice to keep your cooking equipment and food separate from the oven during the process. 

For best drying results use thick filaments, they are easier to dry, you know why? They have a bigger diameter so most of the surface will be exposed to heat. Also, thinner filaments will not take a certain temperature so it might ruin your spool. You can put thinner filaments in the oven but you need to check every 10 minutes or so to see if you need to lower the temp because thinner filaments might warp or deform due to excessive heat.

Although I tend to use the oven as my go-to solution for drying wet filaments, I should also mention other techniques used by the printing community.

Some people prefer to use a blower dryer instead. This is certainly faster more effective than a regular oven for drying your filaments. I never use this technique since it requires human presence.

Another cheap functional way to dry your spools is by placing them within the temperature stable and airtight environment of an air purifier. This has the added benefit of keeping the filament free from pollens, dust, and other impurities that can ruin the print quality if they end up in the nozzle.

How to properly store filament?

In order to stop moisture from being absorbed by your filament, most suppliers ship their filaments with a tiny bag of silica gel. Silica gel is a desiccant, i.e. a product that absorbs moisture from its environment while being relatively unaffected by the change in the moisture content of that environment.

You should store the ABS and PLA filaments in an airtight container or ziplock bag. Additionally, if you are not going to use your filaments for quite some time, maybe for 6 months or so, then you should store them in lids of mason jars and freeze them. This way any moisture that is absorbed will condense on the lid instead of the filament itself and at least the filament will not end up with little water droplets on it and will look as though it. 

If you can’t do that*, then just fill a box with silica desiccant, or rice, and place your spools on top of the desiccant. After that, just wrap it in a plastic sheet, try to make it as air-tight as possible, and place the package somewhere where humidity can’t reach as easily.

*: I’m personally not willing to give up some much fridge real estate for a spool.

Common ways of ruining your Filament (and how to fix them)?

So far, we’ve been mostly preocupied with humidity, wich is the most probable way of ruining an unused spool. Needles to say, there are many other ways by which we can ruin our filaments, so let’s go through each one of them.

Tangled filament spool

A tangled spool of filament that may cause underextrusion during a print. Source

Seriously, it’s the most common issue I encounter as someone who makes a decent portion of their income 3d printing. The operation of FDM printers is simple. Every printer gets the plastic filament from a reel, which in turn is connected to a spool holder. The printer pulls out the filament from the reel and melts it into a thin string with a hot nozzle.

The plastic filament is actually winded on a plastic or metal spool in the form of circular coils. 1 KG spool can have up to a hundred coils. One end of the filament is tied to the spool and the other end is fed to the printer. When the printer is not consuming the filament, this end is not secured and can move freely. If not properly secured, it will most probably end up slipping under another coil and cause a tangle. If your printer receives its filament from a tangled spool, it will most probably be unable to keep pushing the plastic through the nozzle. It will jam halfway through the print the entire object will be lost. This is quite an irritating, time-consuming, and costly mistake. 

However, tangles are quite easy to avoid. All you have to do is never let the loose end of the filament be free. If it is not in the printer, it should either be in your hand or secured tightly to the holes present in the rims of the spool. 

Keep your filaments away from children, animals, or irresponsible adults!

Having a pet, toddlers, or an irresponsible adult visitor in the house poses a particular problem for 3D printer owners. Filament is cool to the touch. It looks like a shiny cable. It makes cool whirring sounds when it moves. And it has a delicious color. You have probably seen what children or pets can do if they get their hands on a dull-looking roll of toilet paper, now, imagine what they will do to a shiny cool looking roll of filament. Therefore, its best to keep your filaments away. 

Sun Damage

Sun Damage to filaments is caused by exposure to UV light from the sun. Sometimes, your filaments may look fine but you can actually feel or see that the PLA or ABS material feels softer or brittle, thinner, and more pliable. And worst of all, it could potentially have deformed to the point where it’s so brittle that it could easily break off or snap. 

Sun damage mostly happens while the filament is being transported or stored near a window. It is certainly easy to avoid this issue.

The spool is either too loose or too tightly held by your printer’s spool holder

A very common problem with 3D printing is when the spool holder or idler holder has such friction that the spool can not move easily around while printing. This will cause the filament to kink up and not feed easy which can then lead to issues like weak layers, poor adhesion, or even clogs and jams.

To avoid this, make sure the spool holder has friction that is enough to not let it move freely and at the same time not cause any hindrance to the rotation of the spool when the printer pulls it. This can be achieved using a piece of cloth or a zip tie.

Not using a filament guide

A filament guide almost always consists of a Teflon tube. Using it to feed the filament to your printer can help keep your filament from getting tangled up and gives you a little more peace of mind while you are working. It can be very helpful for improving the quality of your prints by making sure that the 3D printer is extruding the filament straight and keeping it from getting kinked or tangled.


Having gone through each one of the possible problems, we can conclude that most of them are not only avoidable but quite easy to prevent. Be sure to implement these recommendations in your usual printing flow and always take a few extra seconds to properly store your filaments. After rendering lots of spools unusable due to my own fault, I nowadays tend to follow all the recommendations that I gave through the article, so rest assured that they are tested and really work. Happy printing!

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