Common Troubleshooting for Pressure Sensitive Paper Testing Failures

　　Pressure sensitive paper (pressure test paper) delivers reliable results only when operated correctly. Users often encounter abnormal test phenomena such as no color development, full over-dark staining or irregular background marks. These problems can be traced to improper grade selection, wrong operation or poor storage conditions.

　　If no red color appears after applying pressure, the most common cause is selecting a film grade with pressure threshold higher than actual load. Another reason is reversed placement of two-sheet film, where non-functional surfaces face each other. Users should double-check the estimated pressure range and confirm the matte coated sides are matched. Also verify that real loading force reaches the minimum trigger pressure of selected film.

　　Uniform deep dark color across the whole area means applied pressure exceeds the upper measuring limit of the film grade. Under this condition, all microcapsules fully rupture, and color density loses differentiating ability. Switch to a higher-pressure grade for repeated testing. Random speckled background stains before loading usually come from pre-pressure during storage, finger squeezing or contamination by oil and solvent. This indicates damaged film and such samples should be discarded.

　　Uneven color unrelated to workpiece shape may come from unstable loading speed or pressure holding time inconsistency. Standardize loading procedure and simulate real production conditions. Always scan the imprint within 30–60 minutes. Delayed reading will lead to color drift and inaccurate quantification. With proper troubleshooting, pressure sensitive paper can provide stable pressure distribution evidence for product design optimization and manufacturing quality improvement.