With many different printing materials it can be challenging to find the right distance for the print-nozzle towards the glass bed-surface. We are now implementing a standard setting for most different materials PLA, ABS en PET-G. Where ABS needs a pretty small distance, PET-G needs more space. The perfect distance is also somewhat depending on your layer hight. Enough variations to give you a headache…

z-offset-slic3r
A good way to deal with this is level the bed with a single paper or feeler gauge, the bed needs to be warm when leveling. Then play with the setting: “Printer Settings” > “Z offset” in Slic3r. (See picture). This way you can adjust the gap between the nozzle tip and the glass surface: -0.1mm means the nozzle will be closer to the glass bed, +0.1mm means it will be further away from the bed.
Typical you adjust only 0.05mm to maximum 0.2mm.