Tannin bleeding is the discoloration of the paper caused by the acid in a paper reacting with tannins in the ink. The process is usually caused by an acidic ink or one that has not been properly neutralized. There are three ways to fix tannin bleeding: 1) Add a small amount of cream of tartar to your ink well. 2) Add a small amount of citric acid to your ink well. 3) Use a good quality paper that is pH neutral and does not contain any tannins.