The printed feature size from a quill pin microarraying system was characterized to predict optimal microarray density from common experimental variables of pin size, solution viscosity, and surface wettability. Features containing fluorescent dye were printed from two solvent systems, glycerol in water and sucrose in water, and observed over a wide range of solute concentrations and substrate wettabilities. Observed feature spreading was used to generate spreading diagrams that predict printed microarray feature dimensions from the water contact angle of the substrate, the size of the printing pin, and the viscosity (or wt% solute) of the printing buffer. In general, feature size was observed to increase with substrate wettability and solution viscosity. A simple model was developed to predict feature density as a function of the above variables.