An experiment with a CO2 laser
cutting of 0.025mm stainless steel required,
due to its ad-hoc nature, manual manipulation of the material sample.
Left hand held the piece of the foil and manipulated it in the focused beam,
right hand operated the laser button. The machine used was the common K40-III "Blue Horror";
its absence of safety annoyances...errrr...interlocks is friendly to such ad-hoc tests.
The beam does fairly little damage to skin; as shown, the injury caused is merely annoying.
To protect the eyes, wearing goggles when opening a running laser, and, when possible,
not opening the lid more than what's enough for inserting a hand, is suggested. CO2 lasers
don't typically penetrate past the cornea but corneal injuries are way more annoying
than little skin burns. (Beware especially of near-IR and visible lasers. These go right through cornea and
the lens focuses them to retina, multiplying their destructive effects and grossly lowering
the energy density needed for damage. Lasting and so far untreatable damage can be caused
by situations CO2 lasers just let you get away with. Near-IR lasers are double treacherous
as their beam is not visible but still able to cause damage.)
Due to focus on the sample and neglect of the rest, the top side of left hand got into the beam line between the left mirror and the head. Beam at about 10mA current, from a 40-watt tube, with a diameter of about 4mm, was keyed for few hundreds millisecond, approximately the human reaction time.
 Approximate hand position in the beam path |
The top layer of tissue was ablated with a semiloud "pop" explosion. The
deeper layers were vaporized and partially charred. The burn was clean and
sterile, cauterized, with minimal amount of thermally damaged tissue, other
than vaporized. CO2 lasers are used in laser surgery for their clean cuts.
The wound was painful, with burning sensation, for first 2-3 hours, then settled down. No pain since then.
At the day 0 image, note the faint thermal damage around the deeper-damaged site. This may have been caused by scalding with steam from the vaporized tissue, or by the lower energy density of the beam around its central area.
Measures were taken to keep the wound site sterile; in addition to a conventional
band-aid, an alcohol tincture of propolis was used to cover the wound
surface for the first three days, until a reliable scab formed (the second and third
day may have been an overkill).
The healing progress suggests it will leave a minor but visible bragging scar.
 Day 0, fresh |  Day 1 |  Day 2 |  Day 3 |
 Day 6 |  Day 7 |  Day 7, scab removed |  Day 8 |
 Day 9 |  Day 10 |  Day 11 |  Day 14 |
 Day 15, scab removed |  Day 19 |  Day 24 |  Day 24, size reference |
 Day 43 |
Such unfocused CO2 laser could be useful for cauterizing of minor infected wounds,
warts, and other small structures to be cleanly removed. Be aware of the possibility
of aerosolization of infection agents present in the structure (e.g. viruses from the
warts). Possible applications are also in laser scarification. A coaxial red
laser to precisely indicate the beam position will be beneficial here.