Many 3D printing filament materials are hygroscopic. This means they absorb moisture from the air, resulting in a "wet" material. Once a spool of material absorbs moisture, its properties change significantly.

When the filament is heated in the 3D printer's nozzle, it reacts differently than usual. The water in the material heats up and expands. This leads to uneven extrusion, which in turn can result in faulty prints.

Onyx, nylon, PETG, PLA, ABS, polycarbonate, PVA and TPU are some examples of materials that are hygroscopic—albeit to varying degrees. We'll discuss these in more detail later in this guide.

The image to the right shows a box containing a Markforged Onyx spool in its protective packaging.

Learn more about 3D printing materials here.

Fortunately, there's an easy way to prevent your 3D printing filament from getting wet: proper storage. Reputable filament manufacturers ship their materials in airtight packaging to prevent moisture from penetrating. In Markforged's case, the spools are heated and vacuum-sealed within the packaging to ensure the material stays dry. The first solution is to store the material in its packaging until ready to use, as this is the best way to protect it.

When it's time to print, you'll want to be as efficient as possible. The longer the material is exposed to air, the shorter its lifespan, so try to schedule a series of prints that will use up the material. Saving the longest print for overnight is helpful. Realistically, though, it can be difficult to use up all the material in one go.

Markforged 3D printers have a feature that allows you to circumvent this issue: Dry boxes.

To ensure the best possible protection, an opened material reel must be sealed in a dry box together with the desiccant pack(s) within 15 minutes.

Each spool of filament ships with a desiccant. Different materials ship with different types and amounts of desiccant, depending on their hygroscopicity. It's important to only use the desiccant packs included with a spool of filament. Too much desiccant or the wrong type can draw more moisture into the dry box.

Here’s a tip from one of our additive application engineers:

Do not hoard desiccant packs in your dry box, as this increases the risk of wet material. The reason for this is that Onyx is more hygroscopic than desiccant packs, and therefore draws moisture from wet packs. The two that come with the spool are conditioned to this spool and help maintain the packaged environment when the filament is in the dry box. Always click the dry box closures TWICE!

He says it's also important to close the dry box properly. The Pelican dry box's latches need to be pushed in so they're flat and won't move. You'll hear two clicks: one when you push the latch down, and a second when it's fully closed. If you're not printing regularly, you should unload the material from your 3D printer. Then you can close the fill tube opening with the small red plug included with the dry box, making the container completely airtight.

The dry box and desiccant packets provide good protection against moisture. Properly stored in a dry box, materials should last up to a year before the moisture content becomes too high for printing.

Just make sure you throw away old desiccant packs!

The large-format 3D printers from Markforged, the FX10 and FX20, do not have dry boxes. Instead, they have material cabinets with individual spool compartments. These offer similar protection against moisture.

Here are some final details and exceptions that should be helpful.

• Markforged dry boxes can also be used for other printers and materials.
• Markforged Metal 3D printing filaments are not hygroscopic and therefore do not need to be stored in a dry box or with desiccant.
• Different materials come with different amounts of desiccant. For example, Markforged Onyx comes with two packs of desiccant, while Markforged Precise PLA comes with one pack of desiccant.
• Composite filaments (continuous fibers) are not hygroscopic, but should be stored at room temperature in a cool, dry place away from direct sunlight.
• Kevlar® continuous fibers should be stored in a bag or container that blocks all light.