There are several factors that account for how long a tattoo takes to remove.
Having a tattoo faded out to prepare for a cover up does take less time than complete removal but both require patience and understanding of the process. As can be seen from the video, the actual time spent with the laser acting on your skin is not long, but your body continues to work on the process of breaking up and extracting the ink long after your session finishes at the clinic.
The laser breaks up the larger particles of ink into smaller parts, small enough to enable your body the chance to target these by encapsulating them and transporting them to your waste disposal system. The things that increase your bodies ability to deal with this foreign matter (ink) include being healthy, drinking plenty of water, getting lots of exercise, increasing the blood flow to the area by massaging the tattoo site.
Any good tattoo removal clinic will tell you that there are a number of factors which determine the length of time it can take to remove a tattoo. These are;
Skin Type - The darker your skin type the more sessions it can take to remove. The darker the skin type (on the Fitzpatrick scale) the more the melanin in the skin can absorb the energy and be affected, interfering with the efficacy of the laser.
Location - The position on the body of the tattoo has a great bearing since the further from the main arteries and veins and heart the more difficult it is to remove the tattoo. The white cells that encapsulate the minute ink particles are delivered by the blood network and so the further from the heart your tattoo is the more time is usually takes to be dealt with by your body.
Amount of Ink - From amateur inking through to dense thick designs on an intense tattoo, the amount of ink deposited and the depth of application play a factor in the time taken to remove. The more ink the body has to deal with the more work it has to do. The body has to do the heavy lifting so to speak and the work expected of it is higher when there is more ink or it is deeper in the dermis.
Layering - If your tattoo is on top of a previous tattoo then working through the layers to break up all the ink particles takes more energy, resulting in a more challenging process. When coupled with darker skin the procedure increases with complexity due to the energy absorption, potential for damage to the skin or burning increases.
Scarring & Tissue Changes - The amont of scarring on the tattoo site affects the removal process due to the difficulty in working with the thicker tissue. Breaking up of ink where the skin tissue density, compactness, possible other foreign matter and reaction to the laser varies can contribute to a more difficult removal. It should be noted that any pre-existing scar tissue will remain after the removal treatment but can be improved with IPL, DermaPen or certain laser sessions.
Colours - Of all ink, black ink is the easiest to remove. As the number of colours increases so does the difficulty in overall removal. Black and red together are absorbed well by specific wavelengths of laser (i.e. 1064nm and 532nm). However, other colours such as certain shades of blue and green, purple or pink and yellow may be very difficult to completely remove. It masy also be that white, pink or peach may in fact turn darker as the result of treatment.
The culmination of these 6 main factors will be used by your removal secialist to determine the number of sessions likely required to remove your tattoo. This should be used to set a realistic expectation of the number of sessions and the time likely required to get the desired result. Remember, your body is doing most of the hard work so do whatever you can to help by maintaining your health!