pH indicator papers are used to monitor the pH of soil, waste water samples in the field, manufacturing processes of textile, leather, pigment and Dyes instantly. Special papers like starch iodide paper are used for monitoring oxidising agents in lab and manufacturing processes.Litmus paper is commonly used to determine whether anything is acidic or basic. Yellow litmus paper is the most common type, and it turns red when anything is acidic and blue when it is basic. In terms of acidity and basicity, however, salt water is neutral.litmus paper. A strip of paper that is chemically treated with a dye named litmus. This strip is placed in the liquid whose pH is being determined.