Here is the black separation on text for our book on Shackleton
Here is a link to explain the technical reasons for Black separation
This process is used to avoid. Colour hazing on text.
Process Color Separation
“Full color” or “process color”, uses four inks (cyan, yellow, magenta, and black) to generate a large spectrum of color. It is a trick: halftones are created from the output files, their intensity depending on how much of each ink is needed at that point to generate the correct color mix. Furthermore, these halftones are set at specific angles, each one about 30 degrees from its neighbor, so that printing them on top of one another does not create moiré patterns. When printing color halftones, it is not necessary for the designer or prepress operator to manually separate the colors; RIPs do that automatically.
Note: it is possible to print separations from the print dialog box in both InDesign and Illustrator. On the Output tab, under Mode, select Separations (host-based) (AI) or Separations (ID). This will make the list of colors active and you will be able to select which ones get output and at what angle. For process color output, it is recommended that you leave the default angles set.
Black separation in Adobe Photoshop
In CYMK Images for print
Go into text layer then go into blending mode.
Click off C Y and M channels only the K black remains.
When you click off the black Channel you want all the text to disappear. That shows that the text is only on the Black (K) layer