Stains composed of single-print paper, cosmetics, blue stamp ink, etc., form dirty fruits, medicine stains, urine stains, rust, mud surfaces, and carbonated substances resembling vermilion fire, which are mostly grayish-black in color. Judging by tactile sensation and visual inspection alone will not be helpful in identifying these stains. For example, fresh sugar stains feel sticky, paint and nail polish stains feel hard; oily stains have a greasy sensation; wax stains feel solid; protein-based stains like egg turn black when scraped, and lipstick stains will fade when rubbed or brushed.