A method of forming a dual cure three-dimensional object by additive manufacturing may be carried out by mixing a first precursor liquid and a second precursor liquid to produce a polymerizable liquid comprising a mixture of (i) a light polymerizable liquid first component, and (ii) a second solidifiable component (e.g., a second reactive component) that is different from the first component (e.g., that does not contain a cationic photoinitiator, or is further solidified by a different physical mechanism, or further reacted, polymerized or chain extended by a different chemical reaction). In the foregoing: (i') at least one reactant of the second solidifiable component is contained in the first precursor liquid, and (ii') at least one reactant or catalyst of the second solidifiable component is contained in the second precursor liquid. Once mixed, the three-dimensional object may be formed from the resin by a dual cure additive manufacturing process.