We introduce a framework for printer calibration. The calibration encompasses ink limitation and linearisation. The visual consistency needed in proofing can only be ensured when the calibration uses visual quantities.We extend the framework to describe printing with multi density inks using ink mixing. We show that ink mixing needs to be incorporated into the calibration. As a further refinement, we propose a technique we call multiple linearisation. It allows to achieve a predefined response with respect to more than one quantity, by exploiting the additional degrees of freedom offered by similarly coloured inks.The techniques are illustrated with an example of a two ink calibration for which it is shown that multiple linearisation significantly improves visual uniformity.