Tattoo removal lasers

Jonathan Kemp originally writes

>Probably everyone knows that tattoo removal lasers are of the same
>spec as conservation lasers but 1/10th of the price--in fact they
>are more or less derived from such lasers.

Martin Cooper writes

>Tattoo removal lasers can cost anything from a few thousand pounds
>to two hundred thousand pounds--they come in many different forms.

My original flatly expressed query was for reports on any
experiences conservators may have had using tattoo removal laser
machines for the care of cultural heritage.

My post was motivated in part to re-address the moribund question of
the differences between cosmetic lasers that originally led to
conservation lasers, given the context of the now abundant supply of
cheap (some less than UKP1k) Q-Switched Nd-Yag laser tattoo machines
with some similarities in general specification to those Nd-Yags
used in conservation.

So from an amalgam of specifications of various tattoo removal
machines from ebay.co.uk:

    Type of Laser: Q-switch ND: YAG laser
    Wavelength: Dual wavelength 1064nm and 532nm
    Pulse Duration: 3.5ns
    Pulse Energy: 0-1000mj
    Spot Diameter: 1~6mm
    Repetition rate: 0-10hz, some eg. 5-40Hz
    Maximum average power: 6W

we can compare this with the general specification as advertised for
a leading UK portable conservation laser:

    Wavelength: 1064nm, 532nm
    Pulse energy: 150mJ per Q-switched pulse
    Pulse duration: 10ns
    Repetition rate: 1-30Hz
    Maximum average power: 4.5W

As Martin Cooper implicitly suggests, one expects a host of good
reasons (other than build quality) for the development of
conservation Nd-Yag lasers from earlier cosmetic ones including, as
others have indicated off-list, different pulse duration, and faster
repetition rate (the cheap tattoo machines are typically 0-10hz,
atypically up to 40hz).  Also a tattoo machine's maximum fluence
also appears often to be into a range above safe ablation thresholds
for eg. marble (some offer up to 3.5J/cm2 others around 6J/cm2) so
the parameter interface needs to be very controllable, as others
suggest.

While they are by no means in depth specifications/comparisons they
do suggest questions about what are the differences and potential
uses (if any), a conservator might have for the cheaper option, or
whether are any damning prohibitions on their use?

Thus another motivation behind the question was to ask whether they
might be appropriate in certain contexts, especially outside one of
optimum circumstances, so as to extend options in less advantageous
situations where access, economics etc mitigate such working
regimes.

Dr. Jonathan Kemp
Independent Stone Conservator


                                  ***
                  Conservation DistList Instance 29:5
                   Distributed: Friday, June 19, 2015
                        Message Id: cdl-29-5-002
                                  ***