Why does PETG string more than PLA?

Because PETG stays runny over a wider temperature range and absorbs moisture from the air, so it oozes from the nozzle during travel moves. Drying the spool, lowering the temperature within the maker’s range and tuning retraction usually reduce the fine threads it leaves.

Stringing is the fine web of plastic left between separate parts of a print, and PETG is known for it.

Why the material behaves this way

PETG softens gradually rather than switching sharply from solid to liquid, so the plastic in the nozzle keeps flowing during travel moves. It is also hygroscopic: it takes up moisture from the air, and wet filament oozes and bubbles more.

What usually helps, in order

Dry the spool. A filament dryer or the drying advice from the filament maker removes the moisture that makes the problem worse. Print at the lower end of the maker’s temperature range. Every spool lists a range, and a few degrees less reduces ooze. Tune retraction. The slicer pulls the filament back before travel moves; the right distance and speed depend on the extruder and are found with a test print from the slicer’s calibration tools. Reduce travel. Settings that avoid crossing open space between parts leave fewer threads.

What not to expect

PETG will rarely print as cleanly as PLA with the same profile. It is chosen because it is tougher, more heat-resistant and better outdoors, and a little stringing is part of that trade.

Where the settings come from

The temperature range, bed temperature and any drying advice come from the filament maker’s label or data sheet, and those figures are the starting point. Slicer profiles from the printer maker for PETG are another good starting point, then adjusted one setting at a time.