- The Q-switched ruby laser (QSRL) has a wavelength of 694 nm, which targets black and blue ink. The QSRL penetrates the skin one millimeter down, lightening affected tissues. Four to five treatments are typically needed to significantly lessen or remove this shade of ink.
- The Q-switched neodymium:yttrium aluminum garnet (Nd:YAG) has a wavelength of between 532-1064 nm. At higher wavelengths, the Nd:YAG can also blast away black and blue ink, while lower wavelengths can remove reddish tones as well as orange and yellow. The Nd:YAG laser penetrates more deeply into the skin, and has a narrower focus point. This makes it better for darker skin, since the laser is less likely to accidentally target melanin on the skin's surface. The smaller spot point also makes it more precise, so it's a good choice to remove permanent eyeliner and smaller tattoos.
- The Q-switched Alexandrite has a wavelength of 755 nm and is typically used to remove green ink. Green is one of the hardest hues to get rid of, since the hue is made up of blue and yellow shades, which are extremely common undertones in skin. (That means that other lasers have a much higher chance of affecting the skin instead of the green ink.) Green ink also takes longer to remove. Total tattoo clearance with the Alexandrite laser requires an average of 10 to 11 treatments. (Long story short, don't get green tattoos.)
Many tattoos are multicolored, so that means a variety of lasers must be used. The more colorful the tattoo, the more challenging it is to erase.