In Vitro Spectral Analysis of Tattoo Pigments

Abstract

Absorption spectra of common tattoo pigments, their reaction to irradiation at 532 and 752 nm, and correlation with their titanium and iron component are important to the selection of an optimal laser device. The objectives were (1) to establish the absorption spectra of common tattoo pigments and India ink and (2) to determine their response to laser irradiation at 532 and 752 nm and correlate this to their composition. Samples of 28 tattoo pigments and India ink were mixed in agar and analyzed with a spectrophotometer. These agar plates were irradiated with Q-switched wavelengths of 532 and 752 nm. The highest absorbance of red was in the complementary spectrum, while blue, yellow, and orange had peaks in the adjacent portion of the visible light spectrum. There is great variability in the absorbance of green tattoo material. Pigment darkening was noted at both wavelengths in all iron-containing pigments except black. It was variable in those containing titanium. Pigments tested responded with either clearance or darkening at 532 nm; however, response at 752 nm was more limited. (1) Tattoo pigment absorption spectra can explain why some colors are more resistant to removal. (2) Pigment darkening is a complex process.