Scraping

Scraping means shaving or paring off thin slices or flakes of metal to make a fine smooth surface. Scraping is used to obtain a true flat surface that cannot be produced by machining or filing.
Scraping is done with the tool called scraper with the help of a prussian blue and surface plate for flatness checking.

First of al  the top of the surface plate is applied with prussian blue. Then the scraped surface is laid over the surface plate and moved back and forth. Then the high spots on the surface will be marked with blue. This high spots are scraped down. This process is repeated until the colour is spread evenly all over the surface.