MaterialsbeginnerUpdated April 2026

Storing 3D Printing Filament: Preventing Moisture Damage

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Quick Answer

Store all filaments in sealed containers or bags with fresh desiccant. Engineering filaments — particularly Nylon, PC, and PPA-CF — should be treated as moisture-sensitive at all times and stored in airtight containers between print sessions.

Filament storage is one of those topics that gets treated as optional until you have a print failure that traces back to a spool that was left out. A few basic habits eliminate the majority of moisture-related print failures.

How Filaments Absorb Moisture

Hygroscopic polymers — materials that attract and hold water molecules — absorb moisture from ambient air proportional to the relative humidity and the duration of exposure. The rate varies enormously between materials:

PLA absorbs moisture slowly and tolerates moderate humidity well
PETG absorbs moisture faster than PLA and benefits from storage in a sealed container
Nylon (PA6, PA12) absorbs moisture extremely rapidly — measurably within hours in humid conditions
PC and PPA-CF are highly hygroscopic and should be treated as dry for a single print session only

Sydney's climate averages 60–70% relative humidity for much of the year, which is high enough to affect most engineering filaments meaningfully over time.

Storage Solutions by Priority

Vacuum-sealed bags with desiccant packs are the gold standard for long-term storage and for engineering filaments that need protection between short print sessions. Pull the air out, drop in a silica gel pack, seal. This is the most effective option for PA12, PA6-CF, PC, and PPA-CF.

Airtight containers (plastic storage tubs with rubber-sealed lids) work well for medium-term storage and for daily-use spools. Add fresh desiccant and change it when the indicator colour shows saturation.

Dedicated dry boxes (sealed enclosures with desiccant and a humidity display) allow printing directly from the sealed environment, which is particularly useful for Nylon and PC during long print jobs. The filament feeds from the box through a PTFE tube directly to the printer.

Open spool storage is fine for PLA in normal workshop conditions. Leave it on the printer between sessions without concern. Do not leave Nylon or PC on an open spool.

Desiccant Management

Silica gel is the most common desiccant and is reusable. When the colour indicator (blue to pink, or orange to clear, depending on grade) shows saturation, dry the desiccant in an oven at 120°C for 1–2 hours to regenerate it.

Silica gel indicating colour change is not the only sign of saturation. In very humid conditions, desiccant can become saturated without a visible colour change. Replace or regenerate desiccant every 2–4 weeks in active use.

Temperature Considerations

Filament is best stored at room temperature — neither cold nor hot. Cold storage (below 15°C) can make some materials more brittle and may cause condensation when brought back to room temperature. Hot storage (above 35°C in direct sunlight) can cause tangling and spool deformation in standard plastic spools.

Keep filament out of direct sunlight. UV degrades many polymers over time, including PLA, ABS, and PETG — exactly the exposure you are trying to prevent in the finished part.

After Opening: What to Do

When you open a new spool, note the date. If you will not use it within a week, transfer it to a sealed bag or container with fresh desiccant immediately. Print directly from the bag or container if possible.

If you are opening a spool that has been stored for several months, even in a sealed container, dry it before your first print session. Desiccant packs have a finite absorption capacity, and seals are not perfect over extended periods.