PITT Artist Pen Big Brush Pens contain four times the amount of lightfast, acid-free pigmented India Ink as the PITT Artist Pen, offering great coverage for work in large formats. The ink is smudge-resistant and waterproof when dry. The Big Brush Pens have a strong, big, nib for wide full strokes and narrow detailed strokes. They are ideal for sketches, journals, cartooning and fine ink drawing.