I am quite a long way through a picture I am producing using Faber and Castell India ink Pitt artist pens. Last night I accidentally dropped one of the darker brown pens onto the picture, leaving a line about an inch and a half in an area that is supposed to left uncoloured. The picture is on thick white card with an ever-so-slightly shiny finish.
Changing my plans to mask/hide the line with another colour is not an option. Is something I can do to remove the line or mask it somehow so that it appears white?