Page 130 - Mike Murphy's Blog Posts

So, much of the frosting we see may actually be due to these epidermal cells ballooning due to rapid temperature rises in the melanin. This was first observed by one of my colleagues, PJ McLeod, in the original clinical studies in Canniesburn Hospital, Glasgow in 1982.
It can easily be demonstrated by firing laser pulses at non-tattooed skin which contains some melanin.
https://videopress.com/v/DQ36FvDN?resizeToParent=true&cover=true&preloadContent=m etadata
Here I used a 1064nm wavelength at just under 4 J/cm2 in a 4 mm spot diameter on tanned skin. As you can see, there is no obvious sign of any frosting - because the melanin absorbs very little of this wavelength.
Obviously, darker skins will react more to the laser energy compared with lighter skins. Likewise, tanned skins (real or fake) will also react, which is why it is always better to wait until the tans have faded.
https://videopress.com/v/FwjXnnES?resizeToParent=true&cover=true&preloadContent=me tadata
532nm wavelength at just under 4 J/cm2 in a 4 mm spot diameter on tanned skin.
Here is a video of my wife's skin (no tattoos) reacting to the 532nm wavelength from a QS Nd:YAG laser. it is clear that 'frosting' occurs, even though there are no tattoo ink particles. This frosting is entirely due to the melanocytes and melanosomes in the epidermis reacting to the laser energy, which is strongly absorbed at 532nm. Note that there is a faint cracking sound when the laser interacts with the skin - but that there is NO tattoo ink!
We saw very similar reactions with the 694nm of the QS ruby laser back in the 1980s. Likewise with the Alexandrite's 755nm wavelength.
Mike’s Blog Posts 130