>         Somebody know something about that amazing thing...?

yes, be careful. have this supplier demonstrate this foil.

I once tried to use this technology. It works by copying the
artwork to a specially coated foil.

The "black-powder" ("Toner") - not sure about the english word -
shall stick at the coat. By "ironing" the Toner should be transferred
to the copper and glued.

The first time I tried to copy someting to the foil the copier
got badly damaged because the coating melted in the copier and
glued everything together.

So I prefer the "old" way. print the artwork at vellum-paper
( kind of paper used by architects, which looks like a milky window )
and use the right light.

my Light source consists of two flourescent tubes manufactured
by philips type TLD-05. 05 is the infomation about the emitted
light spectrum. you can possibly get an equivalent.

with two tubes a 36Watts it takes less than 5 minutes to expose
the copper. Also use ready-coated copper-boards they4ll have constant
coating giving better result.

for etching I (!)  prefer following mixture:

700 ml H20 ( Water ), 200 ml HCL 30% (hydrocloric acid ),
30 ml H2O2 30% "Wasserstoffperoxyd". I gives results at 20Celsius
in about 5 minutes. BE CAREFUL. NEVER PUT WATER INTO ACID
Add the Water first, then ACID, the H2O2 !

If you feel uncertain ask someone more experienced with chemical
agents !

Wear gloves and protective glasses.

( .... means DO IT AT YOUR OWN RISK )

but me and many other have etched artworks an we are still alive.

kind regards

        Stefan