Storage Guide
Filament Storage & Drying
Keep your filament dry, your prints clean, and your desiccant fresh.
Things You'll Need
A short list of gear worth having if you want to store and dry filament properly. None of this is strictly required, but each item makes a real difference.
Filament Dryer
Purpose-built filament dryer
The cleanest solution - holds a spool at the right temperature, often has a feed port so you can print directly from it while drying. Models like the Sunlu S1+, Sovol SH01, or eSUN eBOX are popular choices.
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Desiccant
Rechargeable silica gel beads
Color-indicating silica gel that changes from orange to green when saturated. Recharge at 120°C in the oven and it's good indefinitely. Buy in bulk (500g+) - you'll use it across every storage container you own.
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Storage
Airtight storage bins
Large airtight containers - IKEA SAMLA with a lid, Sistema clip-lock boxes, or Sterilite tubs. Load with desiccant and you have sealed multi-spool storage for a few euros.
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Long-Term Storage
Vacuum seal bags
For spools you won't touch for weeks or months. Vacuum bags pull out nearly all air - and the moisture in it. A hand pump or electric sealer is all you need. I highly recommend the eSUN Upgrade Vacuum kit; it's got everything you need.
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Monitoring
Mini digital hygrometer
Small enough to drop inside any storage box. Shows temperature and humidity at a glance so you know when to recharge desiccant without opening and exposing the spools.
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Why Moisture Ruins Filament
Most 3D printing filaments are hygroscopic - they absorb water vapor directly from the air. This is not a flaw unique to budget filament; it is a property of the polymer chemistry itself.
How Absorption Works
Water molecules are small enough to lodge between polymer chains in the filament. Over time, even a sealed environment with residual humidity allows moisture to migrate into the plastic. You cannot see it happening.
What Happens When Printed
Water boils at 100°C. Your nozzle runs at 200°C+. Trapped water turns to steam instantly, creating micro-bubbles in the melt. The result: popping sounds, rough surfaces, stringing, weak layer bonds, and foamy appearance in translucents.
Sensitivity Ranking
How Long Can Each Material Sit in Open Air Before Print Quality Suffers?
Approximate time each material can sit unsealed indoors before you'll notice print quality problems (popping, stringing, weak layers). Based on community experience at typical 40-60% indoor humidity. Higher humidity environments will shorten these times significantly. Shorter bars = seal it sooner.
How to Know If Your Filament Is Wet
You cannot tell from looking at a spool whether it has absorbed moisture. Watch for these signs during and after printing.
Popping, crackling, or hissing sounds coming from the nozzle during a print - steam escaping from the melt.
Excessive stringing or oozing between moves, even with well-tuned retraction settings - wet filament has lower viscosity and strings more easily.
Rough, bubbly, or foamy surface texture on finished parts - steam bubbles burst through the outer wall as it solidifies.
Parts snap unexpectedly under light load - moisture degrades interlayer adhesion significantly, resulting in parts that are weaker than they should be.
Cloudy or frosted appearance in clear or translucent filaments - moisture causes micro-voids that scatter light, ruining optical clarity.
Steam or wisps rising from the nozzle between moves - visible water vapor escaping the hot end.
Inconsistent extrusion width - diameter variation caused by steam bubbles disrupts flow, leading to alternating over- and under-extrusion.
If you hear crackling, stop the print and dry the filament before continuing. Printing wet makes it worse - the heat drives moisture deeper and can also degrade the polymer.
How to Dry Filament
Drying removes absorbed moisture by applying low heat for an extended period, allowing water to evaporate out of the polymer. When in doubt, dry it - even new spools from warehouses may have absorbed moisture in transit or storage.
Drying Settings by Material
| Material | Temp (°C) | Time | Notes |
|---|---|---|---|
| PLA | 45-50°C | 4-6 hrs | Keep below 60°C or the spool will soften and warp [1] |
| PLA+ | 45-55°C | 4-6 hrs | Same temperature limits as standard PLA |
| PETG | 55-65°C | 6-8 hrs | Tolerates slightly higher temps than PLA; absorbs faster too |
| ABS | 65-80°C | 4-6 hrs | Needs higher temperature to drive out moisture effectively |
| ASA | 65-80°C | 4-6 hrs | Same as ABS; both tolerate higher drying temps |
| TPU/TPE | 50-60°C | 6-8 hrs | Keep temp low - TPU softens and deforms easily at higher temps |
| Nylon (PA) | 70-80°C | 8-12 hrs | Most aggressive drying needed; dry before every use if stored open [2] |
| PC | 80-90°C | 6-8 hrs | Highest temp required; a purpose-built dryer is strongly recommended |
Drying Methods
Purpose-Built Filament Dryer
Best overall option. Designed specifically for filament spools, often includes humidity readout, timer, and a feed port so you can print directly while drying.
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Household Oven
Works but requires caution. Most home ovens cannot reliably hold below 60°C, and hot spots can warp spools. Only use with an accurate oven thermometer and keep the door slightly cracked for moisture to escape.
Print While Drying
Some filament dryers include a spool holder and feed port that lets you run filament directly into the printer while it dries. Excellent for Nylon and PETG where moisture re-absorption between drying and printing is a real risk.
Important Warnings
Never exceed the material's softening temperature. PLA spools will fuse and warp at 65°C+. Always verify your dryer or oven actually reaches the target temperature with a thermometer.
Kitchen oven risk for PLA/PLA+. A regular oven set to "low" can easily spike above 60°C. Do not use an oven for PLA unless you can continuously verify temperature with a separate thermometer.
Do not microwave filament. Microwave ovens heat unevenly and can melt, deform, or ignite plastic. Filament is not microwave-safe under any circumstances.
How to Store Filament Properly
The goal is to keep filament below 15-20% relative humidity (RH). [4] Ambient room air is typically 40-60% RH - far too high for sensitive materials. Sealed storage with desiccant is the only reliable solution.
Sealed Bags with Desiccant
Cheapest option. Zip-lock or vacuum bags with silica gel packets inside. Works well for short-to-medium term storage. Use enough desiccant for the bag volume - typically 50-100g per spool.
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Airtight Storage Boxes
Large airtight bins (IKEA SAMLA with lid, Sistema, Sterilite) loaded with desiccant. Good for bulk storage of multiple spools. Add a small hygrometer inside to monitor actual humidity levels.
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Dry Boxes / Active Enclosures
Purpose-built enclosures that maintain low humidity continuously. The best passive dry boxes (Polymaker PolyBox, PrintDry) allow printing directly from the box, keeping the spool dry during use.
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Vacuum Storage
Vacuum seal bags remove most air along with its moisture. Excellent for long-term storage of spools you won't use for weeks or months. Requires a vacuum sealer pump.
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Hygrometer tip: Place a small digital hygrometer inside each storage container so you can read the actual humidity at a glance without opening the box. When it climbs above 20%, recharge your desiccant.
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Recharging Desiccant
Silica gel is not single-use. It can be dried out and reused indefinitely, making rechargeable desiccant significantly cheaper in the long run than replacing disposable packets.
How to recharge: Spread silica gel beads or packets on a baking tray in a single layer. Bake at 120°C for 1-2 hours. [3] The silica will release absorbed moisture as steam. Allow to cool before returning to storage containers.
Color-indicating silica gel changes color when it becomes saturated - typically blue to pink, or orange to green (depending on the indicator type). Recharge when you see the color change. After recharging, it returns to its original color.
Loose beads vs packets: Loose rechargeable silica gel beads are cheaper per gram than pre-packed sachets and can be decanted into any container. A 500g bag of indicating beads will last for years across multiple spools.
Humidity Targets by Material
Quick reference for storage targets. Note that ambient room humidity is typically 40-60% RH - active desiccant storage is required for all sensitive materials, and is good practice for all filaments.
| Material | Target RH% | Sensitivity | Notes |
|---|---|---|---|
| PLA | < 20% | Medium | Degrades slowly; noticeable after days or weeks of open-air storage |
| PLA+ | < 20% | Medium | Similar to standard PLA; slightly more sensitive in some formulations |
| PETG | < 15% | Medium-High | More sensitive than PLA; stringing and surface issues appear quickly |
| ABS | < 25% | Low-Medium | Relatively tolerant; still benefits from sealed storage for long term |
| ASA | < 25% | Low-Medium | Similar to ABS; among the more tolerant filaments |
| TPU/TPE | < 15% | High | Absorbs moisture fast; always store sealed with desiccant |
| Nylon (PA) | < 10% | Very High | Open-air storage for more than 1 hour can ruin it; dry before every use |
| PC | < 15% | High | Requires aggressive drying before use regardless of storage conditions |
Humidity % (relative humidity) depends on temperature. 50% RH in a cold winter room contains less total water vapor than 50% RH in summer. In warm, humid climates, storage conditions need to be especially aggressive.
Common Mistakes
Storing on an open shelf. Even in a "dry" room, ambient humidity is typically 40-60% RH - enough to ruin Nylon overnight and degrade PLA within days. Open shelves are not storage; they are exposure.
Printing without drying first. New spools from some retailers sit in warehouses for months before shipping. Treat all hygroscopic filaments (Nylon, TPU, PETG especially) as potentially wet until proven otherwise - dry them before first use.
Using an oven without a thermometer. Home ovens are notoriously inaccurate at low settings. Guessing the temperature is the most common way spools get deformed. Always verify with a separate oven thermometer before committing a spool to oven drying.
Not recharging desiccant. Saturated desiccant does nothing. If you never check or recharge it, your "sealed" storage container is slowly filling with moisture. Check the color indicator regularly and recharge at 120°C when needed.
Ignoring the crackling sound. Popping and hissing from the nozzle is a clear signal that filament is wet. Continuing to print wet makes it worse - the elevated temperature drives more moisture into the melt zone. Stop, dry the filament, and resume.
Confusing relative humidity with absolute moisture content. 50% RH in cold winter air contains far less actual water vapor than 50% RH on a warm summer day. If you live in a warm, humid climate, your storage setup needs to work harder than someone in a cold, dry region.
References
- Prusa Knowledge Base — "Filament Drying Guide." help.prusa3d.com/article/filament-drying_332086
- Bambu Lab Wiki — "Filament Drying Recommendations." wiki.bambulab.com
- Tom Sanladerer — "How Bad Is Wet Filament Really?" (2021). Moisture absorption testing with PLA, PETG, and ASA. toms3d.org
- Sovol — "Which 3D Printing Filament Handles Humidity Best?" Moisture absorption rates and timelines for common materials. sovol3d.com