Abstract: An erasable black ink composition for use in ball-point pens is disclosed. The composition comprises rubber, a low boiling solvent, a black pigment, a quality adjuster and a lubricant, wherein the content of the rubber is 18.9 to 20% by weight of the composition, the ratio by weight of the low boiling solvent to the rubber is in the range of 1.56:1 to 1.64:1, the ratio by weight of the pigment to the rubber is in the range of 0.8:1 to 0.9:1, and the ratio by weight of the quality adjuster to the pigment is in the range of 1.7:1 to 1.8:1. Traces of the ink can be erased by a rubber eraser within an initial period of time.

Abstract: An aqueous ink composition, suitable for use in writing instruments including an ink passage made of a plastic material, consisting essentially of water, a water-soluble dye and a naphthalene derivative as essential ingredients and a glycol or a polyglycol as a moisture-retaining agent, a very small amount of a surface active agent as a penetrant, an anti-mold agent and other additives as optional ingredients. The naphthalene derivative imparts affinity for the plastic material.