Spectroscopic measurements on copper vapors emitted by the cathode are presented for magnetically rotating arcs in a coaxial copper electrode geometry. The maximum temperature of a 100-A are column burning in contaminated argon is shown to be lower than 8000 K. A maximum Cu density of 5 x 10(21) m(-3) is observed when argon is contaminated with 1% CO, while it is larger than 10(22) m(-3) with 1% nitrogen contamination. The copper vapors emitted by the cathode explain the low temperatures observed. Cases of surface control of the are velocity at the cathode and radial losses of copper vapors out of the are column are observed from specific parameters describing the are profiles. Evidence is given for a copper ion recombination zone extending 2 mm from the cathode in the nitrogen contamination case.