Synthesis of monoclinic celsian barium aluminosilicate by a three-step firing technique with or without the addition of Li 2 O was studied using X-ray powder diffraction (XRD). Prefiring BaCO 3 and SiO 2 at 1150 o C to yield BaSi 2 O 5 prevents the reaction path to hexacelsian via the formation of BaAl 2 O 4 . Reacting BaSi 2 O 8 with Al 2 O 3 at 1200 o C to yield hexacelsian BaAl 2 Si 2 O 5 (BAS) would encourages the formation of monoclinic celsian nucleus. Finally, the ground hexacelsian powder is annealed at temperatures between 1200 and 1530 o C to promote the transformation of hexacelsian-to-celsian. With the presence of 0.4wt.% Li 2 O, complete transformation to celsian occurs at temperature as low as 900 o C in 4h.