A piece of pH indicator paper is used to gauge the acidity or alkalinity of a solution. Different types of pH indicator paper are used depending on the type of test and level of accuracy required, such as red or blue litmus paper.
The pH scale ranges from 0 to 14, where a measurement of 0-6 denotes acidity, 7 represents neutral, and 8-14 shows alkalinity. This measurement is obtained by comparing the color of the indicator paper to a chart after dropping a small amount of the solution onto the paper. Indicator paper should never be dipped into the substance being tested, as the dye from the paper can contaminate the solution.