Force K processing is presented to replace gray color values of input data with only levels of black ink/toner when color management is not specified in the print job. A system converts input data of a print job to a CMYK color space of a printer by processing a lookup table of color values for the color space of the input data based on a detected color space of the input data to identify gray color values of the lookup table. The system also determines that these gray color values produce an output in the CMYK color space of the printer that includes one or more of cyan, magenta, and yellow color components. The system replaces the gray color values with black color values and corresponds the black color values of the lookup table with gray color values of the input data for conversion of the input data.