How do you identify damp filament?
You usually only find out your filament is damp while printing. The moisture in the strand evaporates in the hot nozzle, causing tiny steam explosions. This results in the following sights and sounds:
- Crackling or hissing sounds from the nozzle, as if something is frying.
- Steam or tiny bubbles escaping from the printed strand.
- Stringing and a rough, dull surface instead of a smooth, glossy finish.
- Weak layer adhesion, causing your print to break easily or fall apart.
- Inconsistent extrusion: too much material in one spot, too little in another.
Do you recognize one or more of these signs while your printer settings are correct? Then there is almost certainly moisture in your filament.
Why does filament get damp?
Most filaments are hygroscopic: they absorb moisture from the air. A spool left out in the open slowly absorbs water from its surroundings, even if you can't see it.
The more humid your room, the faster it happens. That’s why a fresh spool often prints cleaner than one that’s been sitting next to your printer for months.
Not every material is equally sensitive to this. Nylon is the biggest culprit and can become too damp within a day. Flexible materials like TPU, PETG and the soluble support material PVA absorb moisture quickly. PLA and ABS are slower, but they also become damp over time. In other words: no filament is safe if you store it incorrectly.
The biggest enemy is an open spool in a damp room, such as a garage, shed, or basement. Filament that you have just opened and then simply leave on the printer picks up a little moisture every day.
A spool that is in its original, unopened packaging with desiccant, on the other hand, will stay in good condition for a long time. The moment you open the packaging, the clock effectively starts ticking.
Is damp filament harmful to your printer?
The chance that moisture will permanently damage your 3D printer is very small. The biggest risk is that the steam and irregular flow will temporarily clog the nozzle or cause under-extrusion. You can solve that by using dry filament and cleaning the nozzle.
The real damage is mainly to your prints: weak, ugly results and wasted material. Reason enough to take moisture seriously, but no reason to panic about your machine.
What can you do about damp filament?
When drying filament, you evaporate the absorbed moisture out of the strand. This can be done in three ways.
- A filament dryer is the most convenient: it keeps the temperature and airflow constant, and you can often print directly from it.
- If you have an enclosed 3D printer, use your printer!
- A convection oven also works, provided you can set the temperature low and accurately.
- And a food dehydrator is an inexpensive alternative that works surprisingly well. Whichever method you choose, follow these steps.
Confirm that it is moisture. Are you getting messy prints even though the temperature and speed are correct, and does the filament break easily? Then moisture is the most likely cause.
Choose a drying method. A filament dryer is the most convenient and safest. Set the correct temperature. Always stay well below the glass transition temperature, otherwise the spool will deform. As a general rule, count on PLA around 45°C, PETG and ABS around 65°C, and nylon around 80°C.
Give it enough time. Aim for four to 12 hours, depending on the material and how wet it is. Nylon and PVA need to be on the longer side.
Store it dry immediately. Put the dried spool directly into an airtight box or vacuum bag with fresh desiccant, otherwise it will absorb moisture again in no time.
A quick warning: never put filament in a regular microwave and don't use an oven temperature that's too high. The spool will warp or clump together, and you'll lose your filament anyway.
How do you prevent damp filament in the future?
Drying is the solution after the fact, but prevention is a lot less work. The golden rule is: store filament in a dry, dark, and airtight place. With a few tools, it's effortless.
A filament dryer pulls the moisture out of a wet spool and keeps your filament dry while you print. A popular choice is the SUNLU FilaDryer S2. For spools you're storing for longer, put them in vacuum bags with a pump: you suck the air out and the filament stays bone-dry. Place a packet of silica gel in every box or bag to absorb any remaining moisture; it's easy to reuse in the oven.
If you want to know how dry your storage really is, add a hygrometer. Aim for less than 15 to 20 percent humidity. This is especially important for nylon, TPU, and PVA, while PLA will do just fine with a sealed box and some silica gel.
For the most sensitive materials, there's one more golden tip: print directly from a dry box or filament dryer. This keeps the filament warm and dry right up until it enters the nozzle, giving moisture no chance. Especially with nylon, that's the difference between a failed print and a perfect one.
And how long does dried filament actually stay good? That depends on the material and your storage. In an airtight box with fresh desiccant, a spool will last for months without any issues.
If left out in a damp room, sensitive filament like nylon can be damp again within a day. Storing it properly after drying is just as important as the drying process itself.
Prefer a perfect print every time, without the hassle?
Drying filament and keeping it dry is just part of being a dedicated maker. But if you only print occasionally, a closet full of dryers and vacuum bags might be a bit much.
It doesn't have to be. Send us your design and we'll print it using fresh, properly stored material on printers that handle every filament perfectly. That way, you get a clean print without having to deal with moisture and dryers yourself.
