Abstract: A marking composition erasable from both porous and non-porous marking substrates using substantially non-abrasive mechanical erasers. The marking composition preferably has a viscosity of less than about 10 cps and a surface tension between about 20 dynes/cm and about 40 dynes/cm and is particularly well-suited for use in capillary feed markers and similar writing instruments. In a first preferred embodiment, the marking composition comprises a water-insoluble colorant and a blend of two different non-carboxylated styrene-butadiene latex emulsions. The first latex emulsion, an embodiment of which is commercially available as PLIOLITE.RTM. LPF-2108, contains about 40% total solids by weight and has a viscosity of about 30 cps, a pH of about 11.2, a Mooney value of about 150-160, a surface tension of about 55-60 dynes/cm, and a bound styrene content of about 21-29%. The second non-carboxylated styrene-butadiene latex emulsion, an embodiment of which is commercially available as Butofan.RTM.