I washed out my brush pen last night because the ink was drying up in the pen. I used hot water and bar soap and worked it into the base of the bristles with my fingernail. It took a while to get clean, but I eventually got the bristles clear again. When I used it again the lines were gray and I had to draw a million lines to get the water out of it. Once it got close to being solid black, I drew this on sketch paper.