The Congo Red test paper is used to test narrow-range acidic solutions. Congo Red Test Paper is used in acid washes for metal plating where pH values are very low (pH 1.0-3.0). The Congo Red indicator remains blue below pH 3.0, then gradually turns to a brilliant red above pH 5.2.

Instructions:

1. Remove one Congo Red test paper from the vial, being careful not to touch the strip anywhere other than where you grasp it with your fingertips.
2. Dip the strip into the solution to be tested for 1-2 seconds and remove.
3. The Congo Red indicator remains blue below pH 3.0, then gradually turns to a brilliant red above pH 5.2