If you work in a laboratory on a daily basis, you will know that there is more to cleaning than meets the eye. Clean and, especially, residue-free laboratory glassware is essential to safe and successful work in the lab. Various reprocessing processes are used for the value-preserving cleaning of laboratory utensils. These depend on the particular contamination of the laboratory glassware. The Dr. Weigert tutorial series “Laboratory glassware reprocessing” provides tips and recommendations for daily laboratory practice on how to clean typical contaminants on laboratory glassware efficiently and with no residue. Laboratory glassware is often inscribed for labelling. A range of markers and felt-tip pens are available for this. The various colours such as green, blue and black consist of differing dyes. Removing the residue of these dyes is difficult, and the results can vary. In this tutorial, Dr. Weigert provides tips and recommendations for removing stubborn marker residue and felt-tip pen residue.