Stringing and Oozing

Stringing (fine hairs) and oozing (blobs/zits) happen when melted plastic keeps flowing during travel moves. The most effective fixes are usually: dry the filament, run the lowest nozzle temperature that still bonds well, use sane retraction for your extruder type, and make travels fast and “hidden” (inside infill or avoiding perimeters) so any ooze doesn’t get dragged across open gaps.

TL;DR

If you see hairs between parts, dry the filament first and drop nozzle temperature 5–10 C at a time; then tune retraction (less for direct drive, more for Bowden) and use fast, perimeter-avoiding travel moves so any ooze doesn’t get pulled across open space.

Stringing and OozingTopic-specific diagram for the concept, checks, and tradeoffs in this lesson.Strings or blobsMoisture signs?Dry filamentToo hot?
A decision-style map helps beginners quickly pick the highest-impact fix (moisture, temperature, retraction, travel) based on what they observe on the print.

What You’re Seeing (and why)

Stringing looks like thin hairs or webs between separate features. Oozing shows up as small blobs or zits where a travel move starts or ends. Physically, the hotend is a pressurized reservoir of molten plastic; during travel moves there’s no place for plastic to go, so any remaining pressure plus heat and gravity can push a little melt out of the nozzle. That ooze gets stretched into strings when the nozzle moves away.

Fast triage in order (highest impact first)

  1. Moisture check: listen for popping/hissing, look for extra fuzz, and note if stringing worsens after the spool sits out. Dry the filament or swap to a known-dry spool.
  2. Temperature: lower nozzle temperature in 5–10 C steps until strings drop, stopping when you start to see under-extrusion, weak layer bonding, or a rough surface.
  3. Retraction basics: confirm retraction is enabled for the filament and for the feature types you’re printing (some slicer rules can disable it in certain cases).
  4. Travel behavior: increase travel speed and enable options that keep travels off visible walls (avoid crossing perimeters / keep travel within infill / travel avoidance). Long, slow travels across open air exaggerate stringing.
  5. Nozzle cleanliness: wipe off burnt residue on the outside of the nozzle (when hot and safely accessible). External gunk can grab and stretch plastic into hairs.

Symptom to likely cause (and first fix)

Long, wispy hairs between separate towers or gaps

Likely cause: Nozzle too hot, wet filament, or retraction too low/slow

Fix: Dry/swap filament first; then lower temperature 5–10 C and increase retraction distance slightly (or speed, within your extruder’s limits).

Thick strings plus blobs at the start/end of travel

Likely cause: Too much molten pressure or excess flow; retraction/priming not balancing pressure cleanly

Fix: Lower temperature; confirm flow/extrusion multiplier isn’t high; add a small retraction increase if needed.

Stringing is worst only on long travels across open space

Likely cause: Long travel time lets ooze accumulate and get stretched

Fix: Increase travel speed and turn on avoid-crossing-perimeters / keep travel inside infill when possible.

Stringing suddenly appears after many good prints

Likely cause: Filament absorbed moisture; nozzle has residue; or a partial clog causing inconsistent flow/pressure

Fix: Dry/swap filament; clean nozzle exterior; then run a cold pull or cleaning routine.

Retraction changes barely affect the result

Likely cause: Mechanical issue in the filament path or hotend (play/leak), or retraction is effectively disabled by slicer rules

Fix: Inspect Bowden couplers/PTFE/hotend seating for looseness or leaks; verify retraction is active for this material and print features.

What to change without chasing your tail

Change one thing at a time
Temperature, retraction, and travel settings interact. Adjust one setting, reprint the same small test, then decide.
Look for the tradeoff point
The goal is minimal stringing while keeping good layer bonding. Too cold or too much retraction can cause under-extrusion or weak parts.
Retraction depends on hardware
Direct drive usually needs shorter retraction; Bowden usually needs longer because the filament path is springier.

Quick test print to diagnose stringing

  • Two-tower stringing test: two small towers with a gap forces repeated travels and makes improvements obvious.
  • Use the same filament, fan setting, and layer height while tuning so you can compare results.
  • After a temperature change, wait for the hotend to stabilize for a minute before judging.