Visual Inspection: In traditional handmade genuine indigo calico, the reverse side of a single-sided printed fabric will only have a slightly lighter color in the corresponding white area. In double-sided printed fabric, the pattern on both sides will be almost identical, and there will be slight misalignment when matching patterns by hand.
Machine-made counterfeits will have a noticeably lighter and uneven blue color on the reverse side, and the white area on the reverse side of a counterfeit will appear mottled.
Burning Test: Genuine fabrics use plant-based indigo dye. When the edge of the fabric is ignited and then comes into contact with white paper, it will leave a blue mark due to indigo's sublimation characteristic at 160℃. Counterfeits often use chemically synthesized dyes, which will not leave this characteristic mark after burning.
Professional Testing: Refer to the group standard "Analysis and Identification Method of Natural Plant Dyes for Textiles: Indigo" for analysis. Liquid chromatography analysis and spectral comparison can be used to detect indigo content and impurities. Simultaneously, fiber content, color fastness, pH value, and other indicators should be verified to determine if it meets the requirements for genuine products.
