glycol ethers such as propylene glycol monomethyl ether and glycol ether esters such as propylene glycol monomethyl ether acetate these may be used either alone or as mixtures the content of such water soluble organic solvent is preferably within the range of 1 by weight to 40 by weight relative to the total amount of the ink composition if the content is less than 1 by weight the resultant ink dries too fast at a pen tip on the other hand if the content exceeds 40 by weight the resultant ink dries too slow on paper as required the ink composition may contain appropriate ph adjustor pseudo plasticity fomation agent rust preventive agent antiseptic agent antifungal agent and the like examples of specific ph adjustors for use in the present invention include caustic soda sodium carbonate alkanolamine and ammonia usable as the pseudo plasticity fomation agent are natural polysaccharides and semisynthetic cellulosic polymers selected from generally used water soluble polymers more specifically exemplary natural polysaccharides include guar gum locust bean gum weran gum rhamzan gum xanthan gum and the like which have polymeric structure such as obtained by polymerization of monosaccharides such as glucose galactose rhamnose mannose and a glucuronic acid salt the semisynthetic cellulosic polymers include methyl cellulose ethyl cellulose and carboxymethyl cellulose which are rendered water soluble by esterifying or etherifying the hydroxyl group of cellulose examples.