Check the listing for details. Congo Red Test Paper [Vial of 100 Strips]. Condition: New. Listed at 8.99 USD. Pocket-sized, lightweight vialNo color chart necessary100 test strips Congo Red Test Paper 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: 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. Dip the strip into the solution to be tested for 1-2 seconds and remove. The Congo Red indicator remains blue below pH 3.0, then gradually turns to a brilliant red above pH 5.2. NOTE: The solution must be water-based. DISCLAIMER: Bartovation products are not approved for use as medical devices and should under no circumstances be used for any health related purposes. Products and product information is for informational purposes only and not intended for use to diagnose, treat, cure or prevent any medical condition.