If Rick Quann of INKnet Systems is correct, long-run web printers feeding multiple presses from  ink totes and tanks are using a lot more ink than they are accounting for – and that “missing” ink is cutting into profits, increasing manufacturing and shipping costs, and putting extra burden on the environment. It all comes down to the viscosity of the ink, says Quann, which diminishes over time as the printing equipment heats up. Conventional flow meters, by design, have a leak path – and as the ink becomes increasingly less viscous, a greater volume of material flows through the leak path and not through the rotary blades that drive the meter. The amount of unaccounted-for ink increases every hour the press continuously runs, at a rate of about 1% per color per hour. In other words, the ink consumption-per-hour at the end of the 8^th hour of a 4-color web run is considerably higher than the consumption-per-hour in the first hour after the job is trimmed in. The “missing” ink doesn’t disappear, however – being warm, it is absorbed into the fiber of the sheet being printed. According to Quann, the key to more accurately measuring ink consumption (and being able to recoup the costs of all of the ink used) is to shift from conventional ink meters to volumetric linear piston meters (which INKnet Systems makes), which do not impede ink flow and are accurate regardless of the viscosity of the ink being metered. (An article in the July, 2009, edition of Flow Control magazine explains all of this in a much clearer manner than I could ever hope to do.) Long story short, more accurate monitoring of ink flows lead to better cost estimation of future jobs, and greater recovery of the cost of materials. The green story here isn’t particularly obvious, though a green case can be made. First, using a metering system that does not impede the flow of ink allows pumps to operate with greater efficiency, resulting in reduced consumption of electricity. One can take that argument all the way upstream to the point of generation of the electricity and claim savings in fuel consumption and a reduction in greenhouse gas emissions. On the downstream side, if ink flow monitoring instrumentation were to be coupled with processes that stabilized the viscosity of the ink over the length of the press run, then there would be a reduction in the volume of ink consumed and laid down on the paper -- less ink translates to shorter drying times (and less energy used) and fewer VOCs to destroy (less energy there too). Other benefits include a reduction in ink sludge when printed pieces are ultimately recycled, and reduced shipping-related environmental impacts and costs because  the weight of the finished pieces would be less than if they contained 10% or so more ink. It's not an inexpensive solution. And whether or not changing over your ink flow instrumentation makes sense for your production facility is something only you can answer. But the production cost savings associated with the system, coupled with the upstream and downstream financial and environmental benefits make the linear piston meters worth investigating from both fiscal and green perspectives.