Going up and down

There is no dial to turn at home. The implant is one fixed size, and the only things that change are how many you have in a year and when they fall. Your own skin type sets how much colour a given amount produces, which the original work showed clearly: the same dosing gave different depth of colour in pale skin and in olive skin. A specialist adjusts timing by watching your colour and, where light tolerance is the point, by how many hours outdoors you are getting.