A traditional marble-polishing process using oxalic acid during the final development of a polished surface.
Lucidatura con acido ossalico is the use of oxalic acid as part of the final polishing of marble. It is explicitly demonstrated in the finishing sequence documented by Le voci del marmo.
Etymology
Italian: lucidatura, “polishing,” + acido ossalico, “oxalic acid.”
Sculptor Notes
This is a finishing operation rather than a substitute for proper sanding. A polished surface will magnify scratches and defects that were not removed during levigatura.
References
https://levocidelmarmo.sns.it/lista_video.php; https://www.treccani.it/vocabolario/acido/