I would like to examine two practices: saving color OK sheets and pull sheets, or pull signatures. Over the years, economics, time and space have changed many pressroom practices — some for the good and some for the worse.
Let’s look at color OK sheets (this also applies to sigs). The usual practice is to save one sheet that has been used at press to examine by eye or machine, comparing it with the current sheet that has just been run. The problem is that the sheet is now dirty, because it has been handled before the ink fully dried. In attrition today, the customer might not have stayed for a final color OK, leaving instructions instead.
An OK sheet must be signed by the person giving the OK that it is a perfect sheet — not written instructions. This eliminates many arguments later.
The “Best Practice” in OK sheets is as follows:
Insist that the buyer sign three OK sheets. One for the press, one for the file and one for the buyer.
Keep the OK sheets for at least five years.
Make sure the OK sheets have been OK’d to the proof.
Make sure the OK sheets have been OK’d in a color controlled area with 5000K lights.
Measure the sheet to make sure density, dot gain, trap and color are in a normal range.
For pull sheets/sigs, the normal practice in most plants is not to save pull sheets, or to save them for 30 days. This is very dangerous. I have seen jobs rejected for color variation or defects three or more months later. Without documentation, you have nothing.
The “Best Practice” in pull sheets/sigs:
Pull sheets for measurement and/or visual inspection every 1,000 or 7,000 sheets/sigs, depending on press speed.
Keep the pull sheets/sigs until the job is paid for, plus one year. There is nothing like being safe.
Embrace automatic color control on sheetfed or web presses. For web, this can be an aftermarket upgrade. For sheetfed, currently you need to purchase it with a new press.
Remember, the only way to prove the degree of color variation in a run is the pull sheets. Please keep them.
