An ink comprising: (a) from 1 to 25 parts of surface treated titanium dioxide; (b) from 8 to 25 parts of a first solvent selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol and dipropylene glycol; (c) from 2 to 12 parts of a second solvent selected from the group consisting of 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone and N,N-dimethylacetamide; (d) from 15 to 45 parts of glycerol; (e) from 0.1 to 2 parts of an acetylenic surfactant; (f) from 0.001 to 2 parts of 1,2-benzisothiazolin-3-one; (g) from 0 to 20 parts of polymer particles; and (h) the balance to 100 parts water.