Which two dye-penetrant inspection variants are described?

• 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)

Dye-penetrant inspection comes in two main variants: a visible dye that you can see under normal light, and a fluorescent dye that requires ultraviolet light to reveal indications. The red-dye penetrant method is the classic visible option, showing flaws as red indications under white light. The fluorescent variant uses a dye that glows under UV light, often described as fluorescent green, which enhances sensitivity and makes very small discontinuities easier to detect in darkened conditions. Pairing these two—the red-dye visible method and the fluorescent green-dye method—captures the two standard approaches described for DPI. The other choices mix two visible colors or two fluorescent variants, which does not reflect the standard distinction between visible and fluorescent DPI methods.