Oxalic acid, traditionally used in marble polishing as part of a final surface treatment that develops a bright, reflective finish.
Acido ossalico is oxalic acid. In the marble-finishing practice documented by Le voci del marmo, it is applied during polishing with a hemp or jute pad to increase the brilliance of the marble surface.
Etymology
Italian name for oxalic acid.
Sculptor Notes
This is a finishing material, not a substitute for proper abrasive preparation. Because oxalic acid is chemically hazardous, professional handling, protective equipment, and supplier safety guidance are essential.
References
https://levocidelmarmo.sns.it/scheda_oggetti_relazione.php?denom=acido+ossalico&id=24