An etching reagent that reveals not only the macrostructure and faults, such as piping, segregation, particularly sulfur and phosphorus, and cracks, but also slip lines in mild steel that has been stressed beyond its elastic limit. Composition is 100 mL of distilled water, 100 mL of concentrated hydrochloric acid, and 40 g of crystallized chromic acid, 16 g of anhydrous nickel chloride.