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 color.
Record the color 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 color of your litmus paper to the appropriate color on the scale. Record your results.