Compositions suitable for support in building a three-dimensional object are described. The compositions may include a non-curable component and a curable component not reactive with the non-curable component. The composition may further include a surface-active agent and a stabilizer, wherein the composition has a first viscosity of about 20-500 cps at ambient temperature, and a viscosity lower than 20 cps at a temperature higher than the ambient temperature. After irradiation, the composition results in a solid, a semi-solid or liquid material.