How to Store Filament Properly

Seal, label and store filament according to its instructions.

The essentials

An open spool starts absorbing moisture from the air immediately. PLA absorbs enough humidity in one week at 80% RH to lose 20% of its tensile strength — without any visible sign on the spool itself. The fix is simple: seal it, dry it, label it.

PLA absorbs enough humidity in one week at 80% RH to lose 20% of its tensile strength
— Polymer Degradation and Stability, Vol. 95, Issue 4

Who it is for

Hobbyists and small-team operators running 1–2 printers with a basic stock of PLA or PETG, storing spools on open shelving or printer frames.

What this procedure resolves

An open spool left on the printer frame or sitting on a shelf is absorbing ambient humidity every hour. Most first-time operators don't reseal filament after use. The result: stringing, bubbling, brittle parts, and inconsistent extrusion — all caused by moisture you can't see and didn't know was there.

At Level 1, the storage problem feels invisible until a print fails. By then, the spool has already degraded. The fix costs almost nothing. Leaving it unfixed costs prints, time, and material.

Follow the procedure

1.
Reseal every opened spool immediately after use
Moisture absorption begins within minutes of exposure; don't leave spools open between sessions.
2.
Use zip-lock bags with at least one silica gel packet per spool
A 10g silica packet maintains low humidity inside a sealed bag for weeks; replace or regenerate packets every 1–2 months.
3.
Source dedicated airtight containers or dry boxes for your most-used materials
Commercial dry boxes (e.g. Sunlu S2, PrintDry) cost $30–80 and hold 1–2 spools under active humidity control while printing.
4.
Prioritise PETG, TPU, and Nylon before PLA
PLA is the most forgiving; PETG and TPU degrade noticeably faster in open air and should be your first sealed materials.
5.
Check for moisture before printing any spool that's been open for more than a week
Load a short test section and listen for popping or crackling during extrusion; that sound is trapped moisture turning to steam.
6.
Write the open date on each spool with a permanent marker
You need this information later when you start tracking shelf life and drying history.