Inner negative spaces in letters close up during poster colour lettering. What is the main cause?

Correct answer: The brush being too broad or the paint spreading too much

Small counters, or inner negative spaces, remain open only when the letter strokes are narrow and controlled. A brush that is too broad, or paint that spreads beyond the intended stroke, reduces these spaces until they appear closed. Therefore option A is correct. Guide lines and mounting do not alter the stroke width, while opacity alone does not cause the problem when application is controlled.