dipropylene glycol tripropylene glycol polyethylene glycol and polyproplene glycol alkylene glycols whose alkylene group has 2 to 6 carbon atoms such as ethylene glycol propylene glycol trimethylene glycol butylene glycol 1 2 6 hexanetriol and hexylene glycol thiodiglycol glycerol lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl or ethyl ether diethylene glycol monomethyl or ethyl ether and triethylene glycol monomethyl or ethyl ether lower dialkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl or ethyl ether and tetraethylene glycol dimethyl or ethyl ether sulfolane n methyl 2 pyrrolidone and 1 3 dimethyl 2 imidazolidinone the above water soluble organic solvent may be contained in an amount ranging from 1 to 49 by weight and preferably from 2 to 30 by weight based on the total weight of the ink when the mediums as described above are used they may be used alone or in the form of a mixture the liquid medium may most preferably be composed to contain at least one kind of water soluble high boiling point organic solvent as exemplified by polyhydric alcohols such as diethylene glycol triethylene glycol and glycerol other various kinds of dispersant surface active agent viscosity modifier surface tension.