In an example, a printing device may include a cartridge including a print substance, a belt, and a controller including a processing resource and a memory resource. The processing resource may execute instructions to deposit a plurality of patches of the print substance from the cartridge onto the belt to determine a cartridge density based on a density of a sub-set of patches of the plurality of patches; and adjust a print substance output of the cartridge based on the determined density of the print substance in the cartridge.