Drying and Storing Filament

Why filament gets wet

Prusa explains that most FFF printing materials are hygroscopic: they absorb water from the air, and wet filament may not print as expected. In the hot nozzle that water turns to steam. Prusa lists the signs:

• a poor surface, usually the first sign;
• more stringing than you normally get with that material;
• weak layer adhesion, blobs, bubbling and smoke during extrusion.

If a spool that used to print well starts doing this with unchanged settings, suspect moisture before touching the slicer. The symptoms are covered in Wet Filament Symptoms and Stringing and Oozing.

Which materials need it most

Prusa names polyamide (nylon), PVA and TPU as the materials that most often need drying, and also lists polypropylene and BVOH as highly hygroscopic. PLA is less affected than nylon, but it is not immune. Prusa also notes that on multi-tool printers where idle tools stay warm, moisture can come out in the tool and cause stringing, so it recommends drying even PLA before printing on its XL.

Drying figures come from the maker, and makers differ

There is no single drying temperature for a material. Compare two makers' published figures for their own products Maker spec:

Material	Prusament (Prusa drying table)	Polymaker (product TDS)
PLA	45 °C, 6 hours	PolyLite PLA: 55 °C, 6 hours
PETG	55 °C, 6 hours (all versions)	PolyLite PETG: 65 °C, 6 hours
TPU	60 °C, 4 to 6 hours	See TPU
ASA	80 °C, 4 hours	See ABS and ASA
PC Blend	85 °C, 5 hours
PA11 Carbon Fiber	90 °C, 6 hours	See Nylon

For PLA and PETG, Polymaker's figure is 10 degrees above Prusament's. Neither is wrong for its own product, but you should not dry one maker's spool at the other maker's highest figure without checking. Look for the drying line on the spool label or in the product's technical data sheet, and use it.

Drying methods

Method	What Prusa says
Filament dryer	Purpose-built boxes that remove moisture, often able to feed the printer while drying. Confirm the box's temperature range covers your filament.
Home oven	Temperatures are often imprecise and may not go low enough. Use an external thermometer. Fluctuations can damage filament, especially PLA.
Food dehydrator	Can fit a spool with the trays removed, but usually runs cool. Check it reaches the filament's required temperature.
Lab drying oven	Suggested for high-temperature and carbon-filled nylon materials.

Polymaker adds that airflow matters more than heat: moving air carries away the moisture that evaporates, so good airflow dries filament faster at a lower, gentler temperature, while too much heat can damage it. A dryer with a fan, or a box with air movement, beats a hot closed space.

Storage

• Sealed with desiccant. Prusa recommends a closed box or space with desiccant, or vacuum bags with desiccant.
• Prioritize the thirsty materials. If space is short, Prusa says to give dry storage to the more hygroscopic materials first, and for highly hygroscopic ones to keep them in dry storage or dry before every print.
• Print from a dry box for long prints with nylon, TPU, PVA or BVOH, so the spool does not pick water back up during the job. Prusa recommends dry boxes for keeping humidity low while printing.
• New sealed spools. Polymaker says it dries its filament before shipping and vacuum-seals each spool with desiccant, so a spool whose seal is intact can usually print straight from the bag. Other makers may differ; check their packaging notes.

A simple routine

1. Find the drying temperature and time for your exact product (label or TDS) Maker spec.
2. Dry it in a dryer or other heat source you have checked with a thermometer, never above that temperature.
3. Print a small stringing test. If it is clean, the spool was wet; if not, move on to temperature and retraction tests.
4. Store it sealed with desiccant.