Opacity of ink is inadequate

Pad
Porous and rough	Replace pad
Too flat and soft causing insufficient ink release	Use a firmer and more pointed pad
Cliché
Etching depth is too shallow	Etch a deeper cliché
Wrong type of screen	Test a new cliché with a different screen
Wrong type of cliché	Use a different type of cliché
Ink
Ink too thin	Thicken ink
Ink not completely transferred	Use print pause or air blower to partially dry ink for proper release
Material
Image not brilliant enough due to darkness of parts	Use double hit to lay down an additional ink layer