Blue Ghost Invisible Ink is great for writing secret notes that are only visible under black light. Works best with standard non-printer paper. Bright white papers show less contrast. Noodler's Eternal Inks have been formulated with "bullet-proof" qualities to make them impervious to water, bleach and light. Safe for fountain pens of all types, this ink provides archival quality and is 100% made in the USA. Size: 3 oz