If you only use 100% Black in your layout package (C=0%, M=0%, Y=0%, K=100%), our printing press will only print 100% black in those places. Because paper always absorbs the ink a little, the black will look dark gray. 100% Black is best used for reading texts. But for nice dark black surfaces you better use the following combinations in order to obtain a deeper, heavier black:
Cool Black: C=60%, M=0%, Y=0%, K=100%.
Warm Black: C=0%, M=60%, Y=30%, K=100%.
Rich Black: C=30%, M=20%, Y=20%, K=100%.
You can experiment with the composition of your black, but avoid too high values of the C, M and Y inks. As mentioned earlier, the sum of the CMYK values should never exceed 280%.
Caution with Registration Black Colour
This is a black where each colour consists of 100%, it is used for registration marks such as cut lines and pass crosses, so that they appear on each plate (CMYK). So do NOT use them in your layout.