This Is Why They Talk About Drying Your Filament

I went to start up a print today and loaded an old half-full spool of black PETG into the printer. I ran the filament through the nozzle to purge what was left of the previous filament and, as the white plastic faded to grey and then black, I heard an odd ticking sound coming from the nozzle.

I store my filament in zipper bags with a pack or two of desiccant, but even with those precautions, it only slows moisture down – it doesn’t stop it. It’ll make its way in through any tiny hole in the plastic, and water molecules can slowly make their way between the molecules of the plastic bag. You can’t see it or feel, it but with enough time and the right conditions, it’s enough to saturate the desiccant and start working its way into the filament.

In this case, the bag containing the filament spool had been sitting long enough and had gone through enough temperature/moisture cycles (I store it in the basement) that the filament had absorbed some moisture. The moisture was evaporating and creating bubbles and little pops in the plastic as it went through the nozzle at about 220° Celsius:

Bubbled Filament
You can easily see and feel the bubbles even though the diameter of the filament is only 1.75mm.

If I really wanted to, I could probably still print with it, but the printed surface will probably be rough and adhesion wouldn’t be as good.

Fortunately, drying filament is pretty simple. Machines dedicated to drying filament are available, and while they have trays and covers made to fit filament spools, I found them to be a bit too expensive for my budget. I ended up buying a cheap food dehydrator from my local hardware store and drilling a couple of holes in an old Tupperware container to use as a lid:

Now I just need to let it sit for a while and the filament will be good to go!

4 thoughts on “This Is Why They Talk About Drying Your Filament”

  1. bought the exact same dehydrator. some people are saying the temp isn’t accurate so best to keep an eye on it. what container exactly did you use for cover?

    1. Hi, sorry it took me so long to reply…

      You’ve got a very good point. I check it about every half hour when it’s running – just doing the back-of-the-hand thing. You’ve got me wondering now, though – I should toss a thermometer in there and see how it compares to the dial.

      The container is a Rubbermaid 1.6gal/6.0l. It also has “401A 1” on the bottom, not sure if that’s a model# or useful at all. It works pretty well, although I had to tape up the indents around the rim.

  2. Tried the “Contact Me”, nope!
    SO I wanted to feedback and say thanks.
    Hi, first, I have set up a Pi NAS with your help, I say help, I followed you instructions and without that I would have failed. I have left a comment as it went almost perfectly with a couple of tiny pauses.

    OK, you keep your 3d printer stock carefully dry etc.
    This is what I do and it has worked very well for me.

    First I bought a small beer fridge, OK it was a cheap, small, white table top fridge but after a short time I found I did not need, we moved home, it so it sat empty and turned off.

    A short while after I started 3D printing I found the filament was betting brittle and was told it was probably moisture: I thought about it and decided to buy a Pro Breeze Cordless Rechargeable Mini Dehumidifier (Amazon). I placed it in the fridge with the PLA etc and so far it has been great the filament seems to last forever.
    Fridges do have very good seals and compared to dedicated cabinets are cheap. I had it anyway!

    I hope this is useful to you, your NAS stuff was, super useful, to me.

    1. Hi Peter!

      Thank you for the comment, I’m happy to hear that you found some useful stuff! Sorry the contact form isn’t working yet again. It was doing this a couple of months ago too.

      I really like your beer fridge idea – like you said, the seals will be pretty good, it’d do a great job of insulating the filament from sudden temperature and humidity changes in the room, and you can always put it back into service as a fridge later again if you need it! I’ve never tried a cordless dehumidifier – didn’t know they existed!

      Have a great day!

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