Q: What’s the most common question you get about coatings on uncoated?
A: I get this one once a week: A designer will ask about using a coating to show an effect on uncoated — usually spot varnish. I tell them there isn’t going to be an effect, except maybe the kind designers don’t want to see. If you hit any uncoated paper with gloss varnish, it can look galvanized or mottled, especially in dark areas.
Q: OK, so don’t use gloss varnish. What about dull or matte varnish?
A: You use dull varnish, or dull aqueous coating, for rub protection, to prevent ink from rubbing off when the printed piece gets stacked or tossed around. You know, designers are careful. They look at a piece, then put it neatly on the shelf. In the real world, these pieces get stacked and thrown in the trunk. So you use dull varnish or dull aqueous for protection.
There is a visual benefit to using dull aqueous or varnish on black areas — it makes them blacker. On some of our pieces, we have used an inline and offline dull varnish or aqueous combo. It makes the blackest blacks on uncoated.
Q: What are the best ways to use the two?
A: You can use a dull varnish on printed areas, but don’t use it on white areas — that can cause yellowing. A dull aqueous coating, applied on press after the sheet’s run through the inks, protects the whole sheet. It has the added benefit of sealing a sheet instantly, as the ink can dry underneath the coating. This allows the printer to back up the sheet faster than would be possible using varnish. Aqueous is also more environmentally friendly than varnish.
Q: Any tips for using aqueous coating?
A: If you hit a lighter-caliper sheet with aqueous, which is water based, it can curl the sheet. Even a higher caliper will need the aqueous coating on both sides to balance the sheet. This can mean increased cost.
Q: So how do you decide which to use, aqueous or varnish?
A: Talk to your printer. You can only use aqueous if the press has an aqueous tower. Varnish can go in any ink trough. Look at the economics and how your piece is going to be used.
Q: Getting back to the original issue: How do you get a gloss effect on uncoated paper?
A: Easy: For a shiny effect on uncoated paper, you use clear foil stamp or clear UV laminate. That’s a topic for another good conversation.
We’ll return with Pt. 2 of On Press: Coatings on Uncoated. Here’s more advice: In addition to consulting with your printer, McGuire suggests you get Mohawk publications “Specifying Press Coatings” and “The Naked Truth About Uncoated Paper,” online or from your Mohawk rep. “Naked Truth” has side-by-side comparisons of what happens when varnishes are applied to uncoated stock … not to put too fine a gloss on it.
