Abstract: An ink jet ink is disclosed which comprises a binder, a colorant, a conductivity controller and a liquid vehicle in which at least the binder and colourant are soluble, the binder being a nitrocellulose having a viscosity of 15 centipoise or less as measured by method 1 herein; or a weight average molecular weight of not more than 25,000 as measured by method 3 herein; or the nitrocellulose has both the said viscosity and the said weight average molecular weight;and in that the nitrocellulose has a nitrogen content of at least 9.5% by weight as measured by the method of ASTM D 301-72;and in that the ink has a viscosity of 1.6 to 4 centipoise at 25.degree. C. using a Brookfield DV-11+ viscometer with a number 00 spindle at 60 r.p.m (method 2 herein).