How moist filaments will screw up your 3D-printing

It’s not a myth guys. Moisture in filaments will really screw up your precious 3D-print! – Moist Filament 101

Not so long ago I decided to put this to the test, and in this video (and article below) you can understand what’s happening!


I think the general understanding of most experienced 3D-print users is that you’re suppose to store your filaments well. But why? Well the science behind it might be a little to much for me to test out, but what I understand is that many plastic types, and recipies of polymers includes additives to make a plastic filament as moist-resistant as possible. Meaning that during exposure to dry or humid environments, the filament won’t absorb och dry out the amount of H20 in it.

With that said, it’s been seen and told many times that if you leave a filament “unprotected” for some time, it becomes worse printing with. But exactly what is becoming worse, and how do I detect it? Read on to understand why Moist Filament can ruin your 3D prints

In the video above we talk about a few different tests to try to visualize how the material behaves. I do three experiments that are explained down below.

First things first. Data is crucial here. To try to make the most ouf of this, I measure, cut, tag, and neutralize a BUNCH of samples.


All the samples are then dried in a general application fruit dryer, where I take out the shelves so I can dry complete rolls of filament later on. But first, when all samples are dried, we can start measuring each sample on 3 spots to get a base value of the filament samples dimension. Our goal here is to see if we can measure any filament absorption of moisture (my ideas is to measure swelling here).

This is the type of dryer I used, so if you wan’t to get one (and reward me Anton @ 3D Print – Tech Design with some Amazon kickback) i’d love it of you get this cheap one! (no adjustable temperature). Get this one for more control.

The next phase is to expose these samples to different environments!

  1. I put one third of the samples back into the dryer for a “controlled environment”.
  2. The second third gets stored in a normal office environment (with slightly dryer air)
  3. The last set of samples get stored submerged into water for maximum effect!

After a period of time we get our results! Here you can see the full data set and it’s corresponding changes. Note that I used a random set of filaments I had lying around.

Unfortunately i discovered I had made bad measurements on the Ninjaflex filament, so they are not counted)


I think this really is very interesting to see, and to note that some filaments are almost not likely to be affected by moisture over the long run. Interesting enough is that ABS and Nylon (that are famous for absorbing moisture) behaves differently based on brands. For example, Makerbots (quite expensive) filament seems to do very well!

So enough measuring! It’s time to understand what is happening and how to spot it right?

Well, the best way to see if your spool is bad is to just start extruding some of it. Moist filaments will bubble, crack, fizzle and sound a bit weird when extruder. Usually you can also detect some white smoke during extrusion (specially with a black background on the printer).


So that’s how easy you can now detect your moist filament. Just extrude some and notice the smoke!

Now, I think it’s time to take this into OVERDRIVE and actually print a file with bad and good filament, Right?

Using Simplify3D I made a gcode, put it on the Flashforge Dreamer and then print. The result is quite clear!

The (W, left) is the wet one, and (D) is dry:




So conclusion about moisture in filament

What we learn from this is that the moisture in the filament tends to make it harder to stop/start. When the printer stops extruding, the moisture in the filament still boils and pushes out new material and since the steam moves away, there is a gap left with air/bubbles or just un-escaped steam. So, when extrusion starts again, there is not a solid amount of filament which means that there is a “lag” between when the printer starts extruding and when a solid amount of filament actually comes forward.

Another thing we can see is that the amount of moisture is spread out in the filament. The extrusion is not controlled and due to the small amount of extra puffs of extrusion leads to “wiggly” lines. This is specially visible below the round window on the last image. On the dry filament we see clean lines. the variations are mostly due to non exact diameter and roundness of the filament in combination with what the slicer is told to do. Remember, a machine running 1.79mm filament when it thinks it’s 1.75mm will also extrude more than it’s suppose to. Unfortunately, we’d probably have to live with the small variation in lines for some time. Almost no filament have a perfect round 1.75mm all over the spool. At least I haven’t seen anyone yet…

Last thing; For long time storage of open spools, I recommend a air-tight storage box with silica gel inside. For more quick solutions on damaged spools, i recommend using a cheap fruit dryer instead of any “professional” solutions. Or this dryer with temperature-control.

Hope you learned something as well, and please for the love of 3D-printing gods and troubleshooting… share this post/video with anyone you suspect might have moist in their filaments!

Thank you for taking your time! I hope you enjoyed my guest-writing. Hit me up with questions in the comments field or tweet me at @AntonMansson!

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