By Dana Schafer
Updated Mar 24, 2022
Litmus and pH paper are simple, color‑changing indicators that reveal whether a solution is acidic or basic. When a strip contacts a liquid, its color shifts—red for acids, blue for bases—allowing you to read the pH on the accompanying color chart. While a digital pH meter offers precise numerical values, paper strips provide a quick, reliable estimate of the pH range.
1. Dip the tip of a fresh pH strip into the liquid you wish to test.
2. Hold for 1–3 seconds, then remove the strip.
3. Compare the resulting color to the chart included with the kit.
4. Record the pH range indicated. Tip: Never reuse a strip; always use a new one for each test.
To gauge the acidity of your saliva, take two strips—one colored pink, the other blue. Place each in your mouth for a few seconds, then remove and compare the color changes. If the strip turns blue, your saliva is basic; if it turns red, it’s acidic. No change means a neutral pH.
A pH indicator is a chemical that reacts to hydrogen ion concentration, causing a visible color shift. Litmus paper uses such an indicator to produce its red/blue response. Other common indicators include methyl orange (red to yellow) and crystal violet (purple to green). Comparing these with litmus can help you assess the paper’s accuracy.
To become comfortable reading the chart, test the paper with familiar beverages—water, milk, soda, orange juice—each of which has a known pH. This practice helps you recognize subtle color differences and refine your readings.
