"Painting the Sheet"
This is a term printers use to denote heavy ink coverage. When you "paint the sheet," you are laying down a lot of ink on the press sheet. Why would you want to paint the sheet? Because in certain cases heavy ink coverage adds a look of luxury and abundance to your print job (particularly if the ink is either a double hit—the same ink laid down twice, by two inking units, for a really thick film—or a rich black made up of black and other process colors).
That said, you might need to add a press- or off-press coating (aqueous, laminate, or varnish) over the ink to keep the heavy coverage from scuffing.
Painting the sheet might also cause any ink extending across a fold of a brochure to crack. This depends on the direction of the paper grain relative to the fold and is something an experienced printer will need to take into account when planning and pricing the job.
Painting the sheet also requires more ink, and this affects the price estimate. When you specify printing parameters, let you printer know whether the ink coverage will be "light," "moderate," or "heavy." (These are the accepted terms.) Also, mention whether the ink bleeds (extends off the page on any side of the printed piece).
Depending on the ink placement, painting the sheet (on a poster, for instance, with a large ink border around a lighter central image) might cause "ghosting," faint images repeating elsewhere on the sheet (due to the shift on press from heavy ink coverage to light ink coverage and back again). This is a baffling phenomenon for printers, based on "ink starvation" in certain areas of the press sheet and exceptionally heavy inking in other areas. Your printer will need to take this into consideration and make press adjustments (which include "take-off bars," extra areas of solid ink coverage added outside the image area to even out the flow of ink across the press sheet).
On a multi-page publication (within a signature of a book, for instance), painting the sheet will require more ink in one area than in other areas on the press form. Therefore, "in-line conflicts" can occur, in which adjacent pages (in line on a press sheet) can be adversely affected. For instance, heavy use of cyan on one page can add a bluish cast to images on the page immediately adjacent (below or above) on the flat press sheet.
To clarify the description above, imagine eight pages on one side of a press sheet, four on top and four below. This is one side of a 16-page signature. When the sheet goes through the press, the four pages on the top row enter the inking units first, followed by the four pages immediately below on the sheet. Heavy ink coverage on the top four pages will affect the color across the four pages immediately below. Sometimes the effects are undesirable, like color casts on people's faces. That's why it's prudent to meet with your printer early, to discuss the layout of the publication and the ink usage and coverage. An experienced printer will know how to address these potential problems.
On a digital print job, painting the sheet (with toner, rather than ink) can cause pages to fuse together inside the digital press due to the thickness of the toner film and the high heat of the digital printing process. (The only way to avoid this is to avoid large solids and/or create solids with fewer colors—i.e., less toner overall.)
In all of these cases there will be compromises. Therefore, if you plan to paint the sheet, notify your printer early and arrange to meet with him to discuss the job.
A Postscript on What Makes Static Clings Stick to Glass
A PIE Quick Tips reader recently questioned whether static cling decals really stick to a surface because of a static charge, so I did some additional research and spoke with five static cling printers. All noted that the static clings do in fact stick to windows because of a static charge, not because of a vacuum or any adhesive. Also, they noted that water does not affect the ability of a static cling to stick to a surface. In fact, water can actually increase the surface tension of the glass and improve adhesion.
From a scientific perspective, here's how static clings actually work: When some of the atoms in one surface have fewer electrons than they should, that surface carries a positive charge. Conversely, when some of the atoms in another surface have more electrons than they should, that surface carries a negative charge. This is the nature of atoms. When the two surfaces are brought together, this imbalance of electrons causes the two surfaces to adhere. Each surface attracts the other, because each surface seeks to either acquire or release electrons to remedy the imbalance. This is what creates a static charge, also known as static electricity, and this is what makes printed static clings stick to windows.
[Steven Waxman is a printing consultant. He teaches corporations how to save money buying printing, brokers printing services, and teaches prepress techniques. Steven has been in the printing industry for thirty-three years working as a writer, editor, print buyer, photographer, graphic designer, art director, and production manager.]