Electromagnetically recognizable E13B characters can be printed onto conventional paper by an inkjet printer using liquid magnetic ink. The printer receives data representing an E13B character, and prints the E13B character onto a substrate according to a modified E13B character pattern. The modified E13B pattern provides for an interior of the E13B character to be substantially completely filled, and includes one or more void arrangements arranged and positioned relative to a corresponding internal detection edge, and sized and shaped, to amplify the difference between the upstream magnetic signal detected on the upstream side of the internal detection edge and the downstream magnetic signal detected on the downstream side of the internal detection edge when an electromagnetic read head reads the resulting printed E13B character.