Various paper coatings and their uses
Applying varnish is an inexpensive way to add gloss to your printed materials. Although not as hard as other coatings, varnish does offer some protection; mainly resistance to dirt, smearing, and water. Varnish can be applied in two ways. Overprint/flood which is applied over the entire printed surface for protection and Spot/Pattern which is applied to select elements for emphasis. Varnish can also be color tinted. Gloss varnish reflects more light and adds to the sharpness and saturation of images while matte or dull varnish increases readability by diffusing light and reducing glare. This economical coating provides a mild shine and protection but can yellow paper over time.
- Resistant to dirt, smearing and water
- Can be spot applied for content emphasis
- Not as hard as other coatings
- May yellow over time
Aqueous coatings are fast-drying, water based, protective sealants particularly resistant to smudges and fingerprints. Aqueous formulations afford greater protection than varnish and have gloss characteristics that fall between varnish and UV coatings. A high gloss finish has less rub resistance and conversely, a greater rub resistance reduces the gloss. They are not water/liquid resistant because the cured coating does inhibit complete drying of the inks on the printed surface.
- Higher gloss and clarity than varnish
- Resistant to smudges/fingerprints
- Fast drying
- Does not yellow over time
- Environmentally friendly (Water-Based)
- Allows for glossy finish on lesser grade papers
- Rub resistance varies from gloss to matte finishes
- Not water/liquid resistant
Film-based laminate consists of a clear plastic film laid down over the sheet of paper. Laminates protect the sheet from water, are slow to apply and costly; but provide a strong, washable surface. Film lamination features high gloss with a very smooth, tough finish. This durable plastic film has advantages over liquid coating at a slightly higher cost. Film lamination will not yellow with age, flake off, and is scratch resistant. In addition, the ink is protected from cracking and provides an odorless/wipeable surface.
- Strong, washable surface
- Will not yellow with age
- Ink is protected from cracking
- Slow to apply
UV coating is a liquid based, protective coating which is applied and cured by ultraviolet lamps leaving an extremely high gloss hard finish that is chemical and abrasion resistant. UV coatings are solvent free and emit little VOCs (volatile organic compounds). A gallon of conventional ink will contain anywhere from 300 to 450 grams of VOC while UV inks carry between 20 to 40 grams of VOC based on pigment. It is more difficult to recycle than other coatings. Drying is instantaneous with exposure to ultraviolet radiation. Spot cover, raised effects and a very heavy coating for extra shine and protection are possible. Printing must be done with UV inks or inks that do not contain micro crystalline wax (also called wax-free). Pigments must be heat and chemical resistant. If nonresistant colors are used, the color may fade, change or bleed into unprinted areas. UV inks do not have the problem of cracking when bending or scoring as long as you choose the correct Overprint Clear. An Overprint Clear with the correct Monomer Package will avoid this problem.
- Highest gloss
- Better clarity
- Chemical and abrasion resistant
- Spot over and raised effects possible
- Requires special inks
- Difficult to recycle
- May crack when folded or scored unless the correct Overprint Clear is selected
You will often find different manufacturers have different coating preferences and opinions as it relates to printed materials. Typically these are based on in-house equipment availability, operator experience, and personal aesthetic preferences. While all four press coatings mentioned have advantages and disadvantages, there are situations where each shine.