A precursor material is provided for additive manufacturing of a low-density, high-porosity ceramic part. The precursor material includes a body of refractory fibers and a binder in admixture with the body of refractory fibers. The precursor material further includes a viscosity control additive in admixture with the binder and the body of refractory fibers to provide an overall mixture with a viscosity between about 0.3 centipoise and about 150,000 centipoise.