Thermal Transfer Ribbon (TTR) printing is a useful digital marking technology for printing on-demand bar code labels. Over the past decade, a number of advances have taken place with both the printing mechanism and media to enhance image performance in terms of print speed, image durability, print quality, resolution, and cost of ownership.This technical paper investigates a printing defect referred to as “ink split”, a phenomenon that manifests itself under certain printing conditions. As part of this investigation, the TTR printing model is revisited. Empirical evidence of the ink split defect is reviewed. Conventional thermal transfer ink layer construction is described. A cohesive failure mode is described in terms of the printing model and includes a description of crack propagation that occurs within the ink structure during the printing process.From this analysis we have found that complex ink formulations and multiple ink layer constructions in conjunction with high print speed have the potential to produce this ink split defect. The severity is influenced by temperature and nip pressure conditions. Furthermore, this defect can be reduced and eliminated by several different print system modifications.