Date:Fri, 3 May 2002 16:04:45
Sherry: I wanted to pass along a response on the gravure varnish question you raised. I think you have gotten great answers on the linotype question.
The term "varnish" does not have a direct meaning, but could have two connotations. The first would be as an expression for extender (an additive to ink), but it has nothing to do with the manufacture of cylinders. The second may be the application of "varnish" to a cylinder which is referred to as "lacquer corrections".
After a cylinder is chromed, it is proofed using either at a proof press or on the production press. If there's too much color being applied because cells in a particular image area are too large and consequently, more ink than wanted is applied to the paper, the cell size is reduced by applying a thin coat of lacquer to the subject area.
The application of lacquer involves minuscule amounts of lacquer usage over a year. A typical plant may use lacquer in quantities of a few gallons or less per year. In fact, you'll find the prepress employees storing it in less than pint-sized containers.
After the cylinders are removed from the press (the press run is finished), they are cleaned using dilution solvent, which is the same solvent used to dilute raw ink. Assuming ballard shells, removable chrome/copper plate, are used on the cylinder, the shell is manually pealed off from the base cylinder and sent to a scrap metal recycler. Any lacquer remaining in the shells is disposed of with the shells. The shells are non-haz even with lacquer remaining in some of the cells.
In the case of solid cylinders, they're cleaned with dilution solvent which may or may not remove the lacquer. If lacquer is still present, it's removed with ethyl acetate (again, quantities used are measured in a few gallons per year) and then the cylinder is electro-chemically dechromed.
It has to be removed from the cells of a solid cylinder because it interferes with the effective removal of chrome. Chrome remaining on a cylinder will cause the polishmaster cutting diamond to break. The one exception is a relatively new piece of equipment that can withstand the presence of chrome when cutting the chrome/copper plate off the surface of the cylinder. In this case, the lacquer doesn't have to be removed.
The only waste, for all practical purposes, is the disposable wipes that are used to remove the lacquer (disposable wipes with lacquer/ethyl acetate residue). In terms of cylinder making, publication gravure facilities usually make their own cylinders. Many packaging/product shops outsource the manufacture (engraving/plating) of cylinders.
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