intensify

increase in extent or intensity; "The Allies escalated the bombing"

make more intense, stronger, or more marked; "The efforts were intensified", "Her rudeness intensified his dislike for her"; "Pot smokers claim it heightens their awareness"; "This event only deepened my convictions"

become more intense; "The debate intensified"; "His dislike for raw fish only deepened in Japan"

make the chemically affected part of (a negative) denser or more opaque in order produce a stronger contrast between light and dark