COLORED INK AND WRITING SYSTEM USING THE SAME

PROBLEM TO BE SOLVED: To readily and cleanly carry out erasing of written marks such as drawn picture, letter, etc., and correcting operation by instantly decoloring the written marks by adhesion of water. SOLUTION: Writing is carried out by using a colorless mixed solution obtained by blending a coloring auxiliary containing 3-15 pts.wt. of one or more electron-accepting developing compound selected from the group A consisting of adipic acid, ascorbic acid, benzoic acid, zinc chloride, calcium chloride, magnesium chloride, thiamine hydrochloride, citric acid, glycolic acid, succinic acid, salicylic acid, tartaric acid, tannic acid, nicotinic acid, lactic acid, glacial acetic acid, fumaric acid, propyl gallate, malic acid and phosphoric acid with a colorant containing an electron donative coloring compound coloring from a substantially invisible colorlessness into a visible color by the coloring auxiliary. Writing marks are decolored from a color to colorlessness by coating the written marks with an erasing solution composed of water or water and a surfactant.