Determination of acid resistance of the enamelled surface
1- A few drops of citric acid is dripped on enamelled surface
2- The citric acid drops are covered with a flat watch glass.
3- After 15 minutes, the watch glass in removed and the enamelled surface is washed with water.
3-a Visual inspection: If there is a difference between the acid applied area and the regular surface, the outcome is negative.
3-b Pencil Test: Parallel lines are drawn between the acid applied area and the regular surface. The lines are swabbed by a dry towel. If it is harder to swab the acid applied area in comparison with the regular area, the outcome is negative.
3-c Reflection Test: A light source is showed on the acid applied area and the regular area. If there is a defect of reflection on the acid applied surface, the outcome is negative.
4-d Pencil Test: wet: The test in item 3.6 is applied by a wet towel. If it is harder to swab the acid applied area, the outcome is negative.