Stringing

Prusa describes it as 'hairy prints': small strands of filament left on the model. Its three usual causes are badly tuned retraction, an over-high nozzle temperature — the material is runnier and drips on its own — and damp filament, which boils inside the nozzle and pushes material out unbidden. The right order of attack is to start with the filament (dry it), then lower the temperature in five-degree steps, and only then touch retraction. It can be removed with a heat gun or a knife, but it is better not to produce it.