A colorless liquid ink is provided which yields a distinctive marking color on exposure to normal environmental conditions of temperature and pressure as when used for writing on a sheet of plain paper. This ink may be encapsulated to give pressure-rupturable microcapsules. Autogenous, pressure-sensitive record materials are provided by incorporation of such microcapsules in or on sheets of paper for use singly or in manifold duplicating systems which respond to printing-pressures applied by un-inked printing members.