  Calcium abundance in the atmosphere of Am stars is examined as a function of
their evolutionary state within the main sequence. New spectroscopic abundances
as well as abundances abtained photometrically by Guthrie (1987) are used,
since they are mutually quite consistent.
  The main result of this work is that, contrary to earlier suggestions,
calcium abundance does not tend to be larger in evolved Am stars than in
unevolved ones, for objects distributed along a given evolutionary track in the
HR diagram. The trend appears to be the reverse, if it is present at all.
  For our whole sample of Am stars, there is a significant correlation between
calcium abundance and effective temperature, in the sense that the cooler
objects are the most Ca-deficient, hance have the most pronounced Am
peculiarity. This implies an apparent correlation between calcium deficiency
and age, although the lack of Am stars younger than log(t) = 8.6 seems real.
Our results are fully consistent with the low rate of Am stars observed in
young clusters and with theoretical predictions of time-dependent radiative
diffusion (Alecian 1996).
