Which aspect can affect the efficiency of tattoo removal aside from the amount of ink?

The efficiency of tattoo removal is significantly influenced by skin type. Different skin types can affect how the skin absorbs laser energy, which in turn can determine how effectively the ink particles are broken down and eliminated by the body. For instance, individuals with thicker skin or different skin tones may respond differently to the same laser treatment. Additionally, skin types that are more sensitive or reactive may have a different healing response, impacting the overall effectiveness of the tattoo removal process.

Considering the other options, while the duration of the session can influence the treatment's effectiveness, it is not as intrinsic to the biological and physical characteristics of the individual receiving treatment as skin type is. The color of the surrounding skin could play a role in the laser's absorption and targeting, but it is not a direct factor in efficiency like skin type is. Finally, the technique used for tattooing may influence how deep the ink is placed and its composition, but it does not compare to the inherent attributes of the skin itself that affect absorption and healing.