Filament Moisture and Drying: Complete Guide by Material
How Moisture Ruins Filament
Filament is hygroscopic — it absorbs water from the air. When wet filament enters the hot end, that moisture instantly vaporizes, creating steam bubbles in the melt. These bubbles cause:
- Audible popping and crackling during extrusion
- Rough, bubbly surface texture
- Stringy or brittle layers
- White/cloudy streaks in translucent filaments
- Weak layer adhesion (bubbles break the melt bond)
- Reduced mechanical strength (sometimes dramatically)
The effect ranges from minor (slight stringing in PLA) to print-ruining (brittle, delaminating nylon).
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Susceptibility by Material
| Filament | Moisture Sensitivity | Time to Degrade (Open Air, 50% RH) |
|---|---|---|
| PLA | Low | 1-4 weeks |
| PETG | Medium | 2-4 days |
| ABS | Medium | 3-7 days |
| ASA | Medium | 3-7 days |
| TPU/TPE | High | 12-24 hours |
| PLA-CF / PETG-CF | Medium-High | 2-3 days |
| PA6 / PA12 (Nylon) | Extremely High | Under 1 hour |
| PC | High | 4-12 hours |
| HIPS | Low-Medium | 3-5 days |
| PVA | Extremely High | Under 1 hour |
Nylon absorbs moisture visibly in under an hour in humid conditions. Never leave nylon open.
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Drying Temperatures and Times
| Filament | Drying Temp | Minimum Time | Recommended Time |
|---|---|---|---|
| PLA | 45°C | 4 hours | 6-8 hours |
| PLA-CF | 45-50°C | 4 hours | 6 hours |
| PETG | 65°C | 4 hours | 6-8 hours |
| ABS | 65-70°C | 4 hours | 6 hours |
| ASA | 70°C | 4 hours | 6 hours |
| TPU 95A | 55°C | 6 hours | 8 hours |
| TPU 87A/82A | 50°C | 8 hours | 10 hours |
| PA6 (Nylon 6) | 80°C | 12 hours | 16-24 hours |
| PA12 (Nylon 12) | 80°C | 12 hours | 12-16 hours |
| PA-CF | 80°C | 8-12 hours | 12 hours |
| PC | 80-90°C | 6 hours | 8-12 hours |
| PVA | 45°C | 4-6 hours | 8 hours |
| HIPS | 65°C | 4 hours | 6 hours |
Critical: Do not exceed these temperatures. PLA at 60°C+ will soften and warp. PETG at 80°C+ can deform on the spool.
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Drying Options Ranked
1. Dedicated filament dryer (best for regular use) Products: Sunlu S2, eSUN eBOX Lite, PrintDry Pro. Temperature-controlled, holds one or two spools, some have active filament feed-through so you print directly from the dryer. Range typically 40-70°C.
Pros: purpose-built, safe temperatures, print while drying, no guessing Cons: cost ($30-80), limited temperature range (usually under 80°C — insufficient for nylon/PC)
2. Food dehydrator A standard food dehydrator (Excalibur, Cosori, Nesco) handles 45-70°C perfectly. Most fit 2-3 spools with some tray removal. Temperature accuracy varies — use a thermometer to verify.
Pros: cheap ($50-80 new, less used), works well for all common filaments Cons: not for nylon/PC (doesn't get hot enough reliably), no print-through capability
3. Oven (baking) Your kitchen oven works for most filaments — but verify temperature accuracy with an oven thermometer. Ovens can vary by ±20°C from the dial setting. Do not use convection (fan creates turbulence that can tangle filament). Use lowest setting and monitor.
Pros: you already have one, handles higher temps for nylon/PC Cons: occupies kitchen oven, no simultaneous drying+printing, requires monitoring
4. Printbed heating (PLA only) Place spool on the heated print bed at 45-50°C for 4-6 hours. Works for PLA only — other materials need higher temps.
Pros: free, no extra equipment Cons: PLA only, bed is occupied, uneven heating, slow
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Storage Solutions
Sealed bags with desiccant: the minimum. A 2.5-gallon zip bag with a 50g silica gel packet is cheap and effective for PLA and PETG. Recharge desiccant monthly in the oven.
Dry boxes: airtight containers (Sistema food storage, Really Useful Boxes, Sterilite) with desiccant and a feed-through Bowden coupler. Print directly from the sealed box. Best long-term storage and printing solution.
Vacuum storage: for nylon, PC, and PVA that you're not using for weeks. Vacuum seal bags remove most of the air (and therefore moisture) for extended storage.
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Is My Filament Wet? Quick Diagnostics
Listen: wet filament pops, crackles, and hisses during extrusion. Dry filament extrudes silently.
Look: check extruded filament for bubbles, rough surface, or cloudiness in clear/translucent materials.
Weigh: weigh a spool before and after drying. Even 5g loss in weight confirms moisture was present.
Bend test: snap a short piece of filament. Dry PLA snaps cleanly. Wet PLA bends without breaking (moisture plasticizes it).
Hot end residue: wet filament leaves more residue on the nozzle and around the heat break area.