Describe two methods used for dye-penetrant inspections?

• A. Red-dye method and fluorescent green-dye method
• B. Red-dye method and blue-dye method
• C. Yellow-dye method and orange-dye method
• D. Fluorescent red-dye method and fluorescent green-dye method

Answer: (A)

Two primary approaches in dye-penetrant examinations are the visible red-dye method and the fluorescent penetrant method. In the visible red-dye method, a red penetrating dye is applied, allowed to dwell, excess is removed, a developer is added, and under white light any surface-breaking flaws appear as red indications against a light background. In the fluorescent penetrant method, a dye that fluoresces under ultraviolet light is used; after penetration and removal, a developer is applied and the part is viewed under UV, where flaw indications glow brightly. The fluorescent dye can come in different colors (such as green or red under UV), but the key distinction is that one method is visual under white light and the other relies on fluorescence under UV light.