Wet filament is one of the most common causes of bad prints — stringing, weak layers, popping and a rough surface all trace back to absorbed moisture. This tool gives a safe drying temperature and a duration scaled to how wet your spool is, for every common filament.
How it works
Hygroscopic plastics pull water vapour out of the air. When printed, that water flashes to steam in the nozzle, disrupting the extrusion and leaving voids. Drying bakes the moisture back out at a temperature high enough to drive off water but below the material’s glass-transition temperature, so the spool doesn’t soften and fuse.
dry_time = base_time × moisture_factor- base_time reflects how hygroscopic the material is — Nylon and PVA take far longer than PLA.
- moisture_factor scales the time: light (0.6×), moderate (1.0×) or heavy (1.6×) based on the symptoms you observe.
The recommended temperature is the material’s safe drying temperature; for a kitchen oven the tool suggests running a few degrees cooler because ovens are hotter and less even than dedicated dryers.
How hygroscopic is your filament?
Not all filaments absorb moisture at the same rate. Understanding where your material falls on the scale helps you decide how urgently you need to dry it and how carefully you need to store it afterwards.
| Material | Hygroscopicity | Typical symptoms when wet |
|---|---|---|
| PLA | Low | Minor stringing, slightly rough surface |
| PETG | Moderate | Stringing, bubbles, haze on the surface |
| ABS | Low–moderate | Cracking/delamination worsens; surface imperfections |
| TPU / TPE | Moderate | Stringing, reduced elasticity, inconsistent extrusion |
| Nylon (PA6/PA12) | Very high | Heavy popping, steam, major stringing, brittle layers |
| PA-CF (carbon-filled nylon) | Very high | Same as Nylon but harder to diagnose due to matte finish |
| PVA (soluble support) | Extremely high | Jams, bubbling, colour change — can become unusable in hours |
| PC (polycarbonate) | High | Bubbles, streaks, surface haze |
Recognising how wet your spool is
Diagnosing the moisture level helps you choose the right moisture factor:
- Light moisture: minor stringing on overhangs, slightly textured surface, no audible popping. Common for a spool left out for a day or two.
- Moderate moisture: visible steam or wisps at the nozzle, noticeable popping or sizzling every few seconds, pronounced stringing. A spool that has been open for a week or more.
- Heavy moisture: continuous popping, visible steam, severe stringing, rough surface, weak and brittle layers. Common for Nylon or PVA that has been open for a long time or stored in a humid environment.
Tips for drying and storage
- A dedicated filament dryer or food dehydrator beats a kitchen oven — steadier temperature, purpose-built circulation, and much less risk of overshooting.
- If you use a kitchen oven, verify the actual temperature with a separate thermometer. Many home ovens run 10–20 °C hotter than their dial says, which can fuse a spool.
- Always stay below each material’s listed safe temperature. Never try to speed up drying by raising the heat.
- After drying, immediately seal the roll in an airtight box or vacuum bag with fresh, dry desiccant. Nylon, PA-CF and PVA can reabsorb enough moisture to misbehave within a few hours in open air at normal humidity.
- For very wet spools, drying overnight at the listed temperature is safer than cranking the heat to finish faster.
- If brittleness persists after proper drying, the filament may have suffered UV or oxidative degradation that heat cannot reverse. Very old or poorly stored spools sometimes need to be discarded.