Correcting an error when using a Faber and Castell Pitt artist pen 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?
Semi-gloss white paint is probably your best bet.  First color-match the dried paint on a separate scrap of the same paper.  You may need to color-match the paper.

Since you've used semi-gloss paper, you cannot use a single-edged razor blade to lightly scrape away the ink.