Stack of sheets and method of assuring orientation

A method of assuring correct orientation of a stack of sheets, said stack having a first edge and an adjacent second edge and said sheets having opposite sides with different characteristics, said method comprising providing a colorant marking on the first edge of the stack indicative of proper orientation of the stack, the first edge of the stack being formed of respective first edges of the respective sheets in the stack, the respective first edges of the sheets each being straight without an irregularity and the colorant marking being for at least some sheets at different spacings from the second edge of the stack to provide an indication for a full stack and for a partial stack of proper up or down orientation of the stack.