An ink set includes a pre-treatment fixing fluid including at least two metal salts and a fixable, ultraviolet (UV) curable ink. The UV curable ink includes an aqueous ink vehicle, a pigment dispersed in the aqueous ink vehicle, and a dispersant. A polyurethane polymer dispersion is suspended as droplets within the aqueous ink vehicle. The polyurethane polymer dispersion includes a polyurethane polymer selected from the group consisting of a polyether-based polyurethane, a polyester-based polyurethane, a polycarbonate-based polyurethane, and mixtures thereof. The polyurethane polymer has i) an acid number ranging from 0 mg/g to less than 20 mg/g and ii) a glass transition temperature of less than 0 C. A water soluble or water dispersible photoinitiator is present in the pre-treatment fixing fluid or in the fixable, UV curable ink.