Flux at the core of the lines versus purity of the lines for a given element (Ti) and different stellar types (parameters written at the top of each panel). The total available lines, from VALD, are in grey and the selected golden-subsample is in red. The dashed line is located at our S/N_resoļ threshold of 70, i.e. the lines need to be deeper than this in order to be detected. The other two dotted lines split the S/N range from 0 to 70 into three, within which we can select at least five lines, provided they have a purity greater than 0.6.