Provided herein is a method of forming a three-dimensional object, comprising: (a) providing a carrier and a fill level having a build region therebetween; (b) filling said build region with a polymerizable liquid comprising a mixture of (i) a light polymerizable liquid first component, and (ii) a second solidifiable component; (c) irradiating said build region with light to form a solid polymer scaffold from said first component and also advancing said carrier away from said build surface to form a three-dimensional intermediate having the same shape as, or a shape to be imparted to, said three-dimensional object and containing said second solidifiable component carried in said scaffold in unsolidified and/or uncured form; and (d) solidifying and/or curing said second solidifiable component in said three-dimensional intermediate. The solidifying and/or curing step (d) may increase the elasticity and/or decrease the rigidity of said intermediate in forming said three-dimensional object.