Why moisture in filament is bad for 3D Printing

Learn more about Moisture in 3D Printing and how it affects you.

When browsing around different 3D Print Facebook/G+ groups or just generally talking about 3D Printing you quite often come across failed 3D-prints.  A general reason seems to be moisture in 3D Printing filaments. Lets dig deeper to understand!

Watch the video above before continuing. It will give you an introduction to the test that are listed below. 

The first thing you should know is that the scientific data gathered here around moisture in these filaments are ment to not be specifically quoted, but works as a guidance on behavior of moisture in 3D Printing filaments. Please note that it’s not scientifically verified.

The first experiment on moisture in 3D Printing materials is what’s probably the most scientific test. It really shows each sample and how it’s affected through the tests. Using a digital caliper and a nice spreadsheet I could register quite a few data points. 306 data points to be exact… This is how it went by:


  1. First off, cut off samples. 3x 5cm strips of each brand/type
  2. Tag all the samples in random order. ControlWetRoom
  3. Place all the filaments in the dryer to make sure they are dry. Leave over night at 50 degres celcius
  4. Measure all filament samples in the same order;
    1. Upper measurement (close to tag)
    2. Turn 90 degrees, measure middle
    3. Turn another 90 degrees, measure lower
  5. Add those data points to the excel sheet and calculate the average value to get a basepoint for that filament.
  6. Put the Control samples back in the dryer
  7. Put Room samples on a plate in the room
  8. Place the water samples exposed in water to speed up absorption
  9. Again, measure all the data according to step 4.
  10. Review results!

So, the results are quite interesting. See for yourself! NOTE: Alot of the control samples show an extra decrease due to sitting longer in the dryer. We’re seeing a tiny bit more being extracted for most of them. Also, due to non-exact measurements, some of the values are fluctuating. You should ignore last value and round up.

Values are in 10’s of microns. So 177 = 1,77 mm. I know that’s weird, I just don’t wanna process the excel file again…

A few interesting comments to do about this! Normal/standard PLA seems to be quite unaffected, but Filametives rPLA (that is recycled high quality PLA) absorbs more water. The print experience I have it is still amazing, and the colors to. Just take not to store your filament well, and if you experience issues, moist could be the reason.

It’s commonly known that ABS and NYLON is absorbing moist depending on recipes and it’s interesting to see that it’s actually a big increase for ABS and NYLON. Exception is Makerbot ABS. I guess they might have some additives to avoid absorption. Interesting!

Woodfill is also quite absorbent. Something that you would expect with wood in the filament i suppose. 

PETG is behaving well, I guess that’s another reason why I believe it should be more used for anyone who wants the characteristics of ABS.

The second experiment is much more visual and quick to notice.

I just took the same ABS, put one in a dryer for two days or so, another in water for the same period. Then extruded both of them to see some difference.

As you can see in the video, the left, moist ABS is steamy. Water boils and that’s something you should be able to tell. Make sure you are familiar with what material you are printing here. Some special filaments can still be steamy, but not due to water. So if you are unsure, dry the filament if possible!

When I see that the filament really is affected by moisture I think it’s time to see how clear we can see this.

Experiment 3 is the last one and really shows what you can expect to see from a bad spool of filament. 

To run this test I again put a few meters of filament in water, and a few meters in the drier.

I decided to use the Flashforge Dreamer since it has a nice window to help me film everything. I setup the cameras and ran both prints with the same sliced file just after each other. In this case, standard ABS settings (so the dry one isn’t perfect either). The result is quite clear!




Nice marking of trouble-some areas right? ;).

What we learn from this is that the moisture in 3D Printing filaments 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. I also recommend this one since you can control the temperature.

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 Moisture in 3D Printing Filaments!

About The Author
- 3D-visionary enthusiast exploring the world of 3D-printing.With 12+ years of 3D experience from visualization, VFX and CAD-design and the industry itself, I tend to find interest and ideas from the world around me.


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