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This article was reproduced from the April, 2005 issue of "PrintSavvy", our online marketing newsletter [subscribe me]
Press Coatings
Coatings are applied to protect printed matter from exposure to moisture and extreme temperatures, scuffs and scratches, and frequent handling. They can also improve the appearance of the printed piece. Coatings cannot protect against long term color fading or outdoor weather conditions.
Varnish, aqueous and UV are the three major kinds of coatings used in commercial sheetfed printing. All are available in a range of sheens from ultra glossy to ultra matte. The final appearance of the printed piece can be dramatically altered according to how coatings are specified.
Varnish
Varnish is a petroleum-based sealant which is applied either "in-line" or in a second pass on a press. A gloss varnish will deepen colors on a printed piece, while a matte varnish has a more neutral effect.
In custom print jobs, varnishes can be specified as "flood" (covering the entire sheet), or "spot" (applied only over a specific area), such as an illustration or photographic image. Additionally, combinations of varnishes with different sheens can be applied to provide dramatic, yet subtle, visual effects.
Varnishes are the most flexible of all the coatings, since they may be used on any stock, coated or uncoated, including text weights, and applied over ink without fear of bleeding. Varnishes applied on uncoated stock provide rub protection, but very minimal visual effect. Varnishes are slower drying than aqueous or UV coatings.
At Savoirprint, we provide a glossy or matte flood varnish option on all our cards (postcards, folding cards, greeting cards, business cards, rack cards, etc.) and on sell sheets, brochures and posters. We recommend a matte varnish on all products printed on matte stock with heavy coverage, since ink on matte stock tends to scuff very easily.
Aqueous
Aqueous coatings are water-based and are applied by an inking unit of the press or in a special coater. Aqueous has the advantage over varnish of immediate drying. Since aqueous can be applied over wet ink, seals the printed sheet, and dries immediately, it has the practical advantage for the printer of reducing handling time for cutting and other post-press operations.
The disadvantage of aqueous is that it is water-based and can cause paper curl, particularly on thinner papers. Additionally, certain pigments may bleed with aqueous.
UV
Ultra-violet coatings are the most highly gloss coatings available, although they are less commonly available in dull and matte. UV coatings are based on unsaturated polyesters or polyacrylates, or a combination of the two that, when exposed to ultraviolet light, dry instantly. UV coatings offer excellent rub protection.
UV coatings can be applied inline on a UV press or offline using a silkscreen process. Like aqueous, drying is virtually instantaneous, allowing the print job to move immediately to bindery without extra drying time. While UV coatings are popular on postcards and other card stocks, they are not generally efficient on lighter text weight papers.
While all three press coating mentioned above have advantages and drawbacks, we offer varnish as a press coating, since it is as reliable and consistent as press ink, and can be applied to any printed product that we offer.
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