Abstract: Marking instruments having an improved cap-off life are provided. The marking instruments include a marking tip and a marking fluid. The marking fluid includes at least one volatile solvent and a waxy additive dissolved in the solvent at a level of between 0.05% and 25% by weight. The waxy additive is dissolved at a level which is at least 20% of the amount required to form a saturated solution of the additive in the solvent at 20.degree. C. The waxy additive has a melting point of at least 40.degree. C. and is capable of forming a continuous solid skin over the surface of the marking fluid if the marking fluid is held in an open vessel which permits solvent evaporation from the surface of the fluid.