Patent ID: 8173215

Claim:
A method of continuous ink jet printing comprising: A) supplying a main fluid supply of a continuous inkjet printer with an aqueous fluid composition comprising: an acidic salt of an organic amine; and additional free organic amine; wherein the acidic salt of the organic amine and the additional free organic amine are present at concentrations and in relative proportion to provide a buffered pH greater than about 8 and a resistivity less than about 500 ohm-cm at 25° C., the ratio of equivalents of organic amine to equivalents of acid used to form the acidic salt of the organic amine being greater than 1.1:1.0; B) ejecting a continuous stream of droplets of the fluid composition from a drop generator mechanism; and C) in response to electrical signals received from a control mechanism, selecting between printing fluid drops for marking a substrate and nonprinting fluid drops that are collected, returned to the main fluid supply, and replenished as a function of the resistivity of the fluid composition in the main fluid supply.