Board Thread:Questions and Answers/@comment-27127950-20151027213016/@comment-27392440-20160107034757

Check grand fisher's page on this wiki and it even says that a fellow arrancar shatters his mask to make him an arrancar, with the hogyoku nowhere insight, at the end of the agent of the shinigami arc. Remember that all it really takes to make an arrancar is breaking off their mask, it's just not the ideal way for their power.