The photon-number distribution for the gray-body radiation given by Bekenstein and Schiffer [Phys. Rev. Lett. 72, 2512Lett. 72, (1994] is used to study its nonclassical effects. It is shown that as the absorptivity varies from 0 to 1, the gray-body state changes from an extremely nonclassical state to an extremely classical one. The critical point of this transition is located. It is discovered that the negative binomial state is a special case of the gray-body radiation at the transition

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... hence, it is an example of borderline states such as the coherent state. The explicit expressions for the factorial moments, the Q parameter, the P function, and the nonclassical depth of the gray-body state as functions of absorptivity and temperature are derived. PACS number(s): 42.50.Dv, 42.50.Ar