Slic3r Manual

Unless the material being extruded has a very high viscosity it will ooze from the nozzle in between extrusions. There are several settings in Slic3r to which can help to remedy this.

The retraction settings, found in the Extruder section of Printer tab, tell the printer to pull back the filament between extrusion moves. This can alleviate the pressure in the nozzle, thus reducing ooze. After the subsequent travel move the retraction is reversed to prepare the extruder for the next extrusion.

Retraction settings.

Retraction settings.

Additionally there are several settings in the Print tab which can help control oozing.

See also section : Sequential Printing for another technique which can minimise strings forming between objects.