Board Thread:Questions and Answers/@comment-27127950-20151027213016/@comment-27392440-20160109211659

Urahara's hogyoku was probably never used before the vizards but they still were broken whereas after feeding one hogyoku to the other you get a super vizard like Kaname, so though I admit I could be wrong this seems to suggest an incomplete hogyoku, which Aizen admitted his was before feeding it Urahara's, isn't something you should probably use. Also, after stealing Urahara's hogyoku it WAS mentioned that the hogyoku might be deteriorating from over use but there was never really any evidence to back that up