Spectral region around the three (4238.19, 4262.27 and 4297.06 Å) Tc I lines in our sample of Tc-rich S stars. For comparison purposes, the spectrum of a Tc-poor S star (HD 233158, in blue in the top panels) from S18 is also plotted. The spectra have been arbitrarily normalized and binned by a factor of 1.5 to increase the S/N. The Tc I line at 4238.19 Å could not be used for CD −27°5131 as local normalization was hampered by a nearby cosmic ray hit.