Page 75 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
The following chart (Figure 25) shows how much energy density (fluence) is required to effectively denature hair of different colours and thicknesses. Clearly lighter-coloured hair requires more energy to destroy it since they absorb less energy per pulse. So light brown hair needs more energy than brown hair than black hair!
There is also a difference between thick and thin hair. This is to do with the way heat conducts away from bodies – small bodies lose heat much faster than large bodies. Hence thin hair will conduct heat away rapidly compared with thicker hair – hence they do not remain at high temperatures for any length of time, while thicker hair remains at, albeit lower temperatures, for a longer period of time.
This means that thin hair is better treated at higher fluences than thick hair to ensure destruction (Higher fluence induce higher temperatures and cellular destruction occurs at an exponentially higher rate at higher temperatures). This is counter-intuitive and many operators mistakenly use lower fluences on thin hair thinking that that this is the correct approach.
Permanent Hair Removal
Required Fluency vs Hair Diameter and Color
Spectral range 600-1000 nm
120.0 100.0 80.0 Fluency J/cm2 60.0 40.0 20.0 0.0
Fine 25 um
Thin 50 um
Medium 70 um
Thick 100 um
Hair Diameter
Black Hair
Brown Hair
Light Brown Hair
Figure 25 - Fluence required to damage hair vs hair colour/thickness
So, you must be careful when selecting the proper IPL parameters – you must consider hair colour and thickness in addition to skin colour.
The Hair Growth Cycle
Hair growth is a continuous cyclic process which may be affects by the owner’s hormones, age and nutrition. The cycle consists of four main stages –
________________________________________________________________________ 75 Chapter 3 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2022