How much ink sticks best to the inner layer of the pcb circuit board! Ink viscosity how to better

This question is too general, many factors affect the ink viscosity, such as the performance of the ink, DES line potion etching ability, and to do how thick the ink thickness. We use Debelle ink alkaline etching potion, ink thickness required 8-12 um General ink viscosity control in 40-55 seconds between the ink viscosity.