Solid detergent compositions designed to maintain solid integrity throughout production of the pressed solid, during mechanical conveying and during ejection from molds, are disclosed. Solid detergent compositions having unexpected immediate block hardness without a curing step are provided by inclusion of a hardness additive composition comprising a synergistic ratio of polycarboxylic acid polymer chelants to aminocarboxylate chelants. Methods of making solid detergent compositions and solid detergent compositions having at least substantially similar cleaning performance to solid detergent compositions without the hardness additive composition are also provided.