Multispectral printer characterization requires an effective model to map printer input digital counts into reflectance spectra and vice versa. This paper presents a novel strategy to describe dot gain and interaction among inks in the definition of a printer model employing the Yule Nielsen Spectral Neugebauer equation. The method proposed, that requires the printing and measuring of a training set of 143 colors, has been designed for a four-ink inkjet printer, but its formulation is general and may therefore be extended to be used for characterizing devices having more than four inks. To test the feasibility of the our printer model, we employed an Epson Stylus Color 740 inkjet printer: on a data set consisting of 777 samples, regularly distributed in the HSV color space, we have obtained an average spectral accuracy, in terms of mean root mean squared error, of 0.59% and an average color error of 1.54 ΔE*_ab.