Litmus paper is used to identify whether a chemical solution is acidic, alkaline or neutral. Different litmus papers are used to test different things. Red litmus paper, for example, is used to test the base of a solution. Blue litmus paper is used to test the acidity of a solution, and a neutral litmus paper will change colour to indicate an acid or alkaline accordingly. A pH scale is used to interpret the results of a litmus paper reading.
Choose the appropriate type of litmus paper. If you are checking for acidity, use blue litmus paper. Use red litmus paper to test for a base and neutral paper to determine a solution's pH.
Dip the litmus paper into the solution. The solution should reach halfway up the paper to give a clear reading.
Remove the paper from the solution and hold it between your fingers. Wait for the paper to change colour.
Record the colour change of the litmus paper. If the blue paper turns red, then the solution is acidic. If the red paper turns blue, then a base is present in the solution. If you are using neutral litmus paper, refer to the pH scale.
Look at the pH scale. Match the change in colour of your litmus paper to the appropriate colour on the scale. Record your results.
Solutions make the paper wet, which gives the appearance of a darker colour. This may cause you to misinterpret the test. Double-check by testing the solution with blue and red litmus paper. If there is no obvious change in colour, then the solution does not contain acid or a base.