Scraping and burnishing are processes normally used to make corrections in images drawn on plates. Because the drawing is cut into the metal, in order to change it you must first cut away what is there. A scraper is faceted, with two sharp blades on each of three sides. You scrape it across the plate. Of course, this leaves new marks, and these must be burnished, or polished out. A burnisher is smooth and curved, and you should use oil on the image before you burnish the grains of the metal, pushing them into one another.