Filament drying schedules by material
Most filaments are hygroscopic -- they absorb moisture from the air. Once water gets into the polymer, printing turns the trapped water into steam, which creates popping sounds, bubbles in the extrusion, stringing, weak layer adhesion, and surface defects.
How to tell your filament is wet
- You hear popping or crackling at the nozzle
- Surfaces look fuzzy or pock-marked
- Strings that look like spiderwebs (not fine wisps -- thick, fluffy)
- Layer adhesion is suddenly poor on a filament that worked last week
- Spool was open in a humid room for more than ~3 days
Drying temperatures and times
Don't exceed these. Higher temperatures can deform the spool or sinter the surface of the filament.
| Material | Temp | Time | Notes |
|---|---|---|---|
| PLA | 45 C | 6 h | Often sold pre-dried; only needed in humid climates |
| PLA+ | 45 C | 6 h | Same as PLA |
| PETG | 65 C | 6 h | More hygroscopic than PLA. Dry whenever you reopen |
| ABS | 80 C | 4 h | |
| ASA | 80 C | 4 h | |
| TPU | 50 C | 8 h | Stays soft below 60. Don't crank the heat |
| PC | 80 C | 8 h | Very hygroscopic. Print straight from dryer |
| Nylon (PA) | 80 C | 12 h | Extremely hygroscopic. Dry before EVERY print |
| Nylon CF | 80 C | 12 h | Same |
| PVA / BVOH | 45 C | 12 h | Used as support. Water-soluble = wet immediately |
Dryer options
- Filament dryer (e.g. Sunlu S2, Eibos, Polymaker Polydryer): purpose-built, $50-150, can print directly from the dryer
- Food dehydrator (e.g. Cosori, Excalibur): works well, ~$70, removes the trays
- Oven: only if it can reliably hold below 80 C. Many home ovens run hot at low settings. Use an external thermometer
- Heated bed + box: cardboard box over your printer's bed, set to drying temp, leave overnight
Storage after drying
Drying is only half the battle. After drying:
- Resealable bag with silica gel (the indicator type that changes color when saturated)
- Vacuum bags work even better, especially for long-term storage
- "Dry boxes" with PTFE-tubed feedthroughs let you print from the dry environment
- Once humidity in the storage container goes above ~30%, replace the silica
Reviving silica gel
Indicator silica that has gone pink (saturated): bake in oven at 120 C for 3 hours. It'll turn blue/orange/green again (depending on the indicator type).
Quick reference: storage humidity
- Below 20% RH: Safe for nylon, PC, PVA
- 20-40% RH: Safe for PETG, ABS, ASA, TPU
- Below 50% RH: Safe for PLA
If your room is 60% RH (most homes), no filament should be open to it.