Catching up with recent research, possibly the only research, on using ketchup to polish glass: A new study takes the process to new levels of precision.
The study is: “High Precision Glass Polishing with Ketchup,” Max Schneckenburger, Stefan Schiffner, and Rainer Börret, Proceedings of the SPIE 11478, Seventh European Seminar on Precision Optics Manufacturing, 114780F, July 8, 2020. (Thanks to Julius Löbel for bringing this to our attention.) The authors, at the Centre for Optical Technologies, Aalen, Germany, report:
“Due to the advantages over conventional polishing strategies, polishing with non-Newtonian fluids are state of the art in precision shape correction of precision optical glass surfaces…. thixotropic fluids like ketchup… reduce the roughness by polishing, without changing the shape of the sample. Tomato ketchup shows a time-dependent change in viscosity: the longer the ketchup undergoes shear stress, the lower is its viscosity. Therefore, in this article, a new processing is put forward to polishing glass surfaces with ketchup containing micro-sized Ce2O. Besides conventional ketchup, curry ketchup and an organic product were tested as well. An industrial robot onto the work piece surface guides the polishing head. The different types of ketchup are compared by means of roughness and shape accuracy and the potential regarding to manufacture high-precise optical glass.”