Paper Finishes: Dispersion Coating

One very common surface enhancement of paper is called dispersion coating. Dispersion coating represents the most watery of available print coatings. Dispersion is defined as a mixture of two or more substances which are present in differing amounts. Several substances are present in dispersion coating. These include wax, defoamers, hydrosols, film formation aids, wetting agents and synthetic, water-soluble resins. As dispersion coating dries, its smooth surface is produced via the sticking together of water-soluble resins during the evaporation drying process.

The Dispersion Coating Process

Dispersion coating is usually applied after four colour or CYMK printing, where paper first passes through each of the four colours and then through a 5th coating unit. However, this coating can also be applied to paper via a system located inside the printing press itself, or via a dampening unit.

The drying of materials coated via the dispersion process occurs naturally. Due to the evaporation of hydrosols and the absorption of the coating itself, drying occurs very quickly. However, in instances where even quicker drying is required, heat can be applied. The inherent matte or glossy properties of paper will be enhanced by the dispersion coating process.

Why Is Dispersion Coating Ideal?

There are many advantages to dispersion coating beyond the facts that it is a very simple form of print finishing, is easy to apply and dries in a very short amount of time.

Any printed material, whether a series of inkjet labels, books or flyers can benefit from added protection when dispersion coating is applied. This protection shields printed materials from most forms of abrasion, as well as makes them slightly water-resistant. In addition, dispersion coating helps to preserve the colour of paper, preventing yellowing due to age. This is possible because the ink becomes bound with the coating once it’s been applied.

Dispersion coating also contains elements which give it an elastic quality. This quality is beneficial for printed documents which require further processing in the form of grooving, film embossing or creasing.

Which Products Are Best Suited To Dispersion Coating?

Dispersion coating can be used on virtually any product that will be printed and distributed. This includes brochures and inkjet labels. However, any items which may require anything to be written on them following printing such as business cards, postcards or flyers may benefit more from other coatings, as dispersion coating makes writing with a ballpoint pen or marker more difficult.

Paper which has gone through the dispersion coating process is also less likely to react well to printing or stamping. This is because the coating slows the absorption rate of ink. As a result, smudging can occur.

Two Potential Solutions

Where having materials coated with the dispersion print finish has been deemed a necessity and writing, printing or stamping will also need to occur, there are two potential solutions.

1) Depending on the intended use of the material being coated, it may be possible to alter both the combination and concentration of the coating so that it is spread onto the paper in a finer and thinner layer.

2) Another solution is to apply dispersion coating not over an entire product, but only in spots. This will allow for some areas of printed material to be stamped, written and printed on.

When considering dispersion coating, it’s a good idea to remember that different printing companies will have different set ups as far as dispersion coating units are concerned. Some coating units will be smaller in size than ink printing units, where others may be larger. However, the size of the coating unity should not affect coating quality or coverage.

Dispersion coating is both a very common and very popular form of print finishing. However, it isn’t the only kind. If there is some doubt as to whether dispersion coating is the ideal choice, an experienced printing professional can certainly provide further insight.

Which Print Coating Is Right For Your Materials – Aqueous, Varnish Or UV? Part I

When you need to add an element of creativity to your printed materials or want to ensure they are protected, do you know which options are available to you? Not choosing the right coating for the paper being printed on can result in a much different look and feel than you originally intended.

There are three main print coatings: aqueous, varnish and UV. Each coating type has its own sub-set of styles. Under the aqueous coating group are matte, pencil receptive, gloss and dry erase, to name a few. Varnish coatings are available in the opaque, matte, satin, gloss and strike-through matte varieties.

What’s the difference between Aqueous and Varnish Coatings?

The aqueous coating, as its name suggests, is water-based. The application of aqueous coating involves the use of a special press unit and a rubber blanket. Varnish coatings can be tinted and are applied in the same way that ink is; on a printing press.

Aqueous Coatings in Detail

An aqueous coating is less likely to turn yellow over time than a varnish. As well, aqueous coatings are used on inkjet labels and other materials which require protection from fingerprints and similar blemishes. Because aqueous coatings dry quickly, projects which utilise them take far less time to complete on professional presses.

One interesting aspect of the aqueous coating is that when applied, it can prevent metallic inks from tarnishing. This is because the aqueous coating seals ink onto paper via air drying. Although it may not occur for a number of years, the aqueous coating has been known to cause certain spot colours to change completely. Finally, paper which is under a certain text weight may wrinkle, curl or distort because of the coating’s water-based nature.

Popular Aqueous Coating Types

There are several popular types of aqueous coating. One is used as primer, and is aptly named primer aqueous. This coating is applied prior to any lamination, or on materials that tend not to be receptive to the application of ink.

Another is called gloss aqueous coating. This particular type is usually applied all over a material. When gloss aqueous coating is applied, it dries right away. This property makes gloss aqueous ideal for small projects that need to be completed quickly.

Pencil-receptive aqueous, as its name suggests causes the material being printed to more easily accept the transfer of pencil, laser and pen inks.

Satin, matte and soft touch aqueous each have their own special properties. Satin has a soft sheen and protects materials, where matte is resistant to scuffs. Soft touch has a luxurious texture and a completely matte surface.

Dry erase aqueous coating is an alternative to lamination with an added benefit: it transforms nearly any paper into a surface that can be written on with dry-erase implements.

Varnish Coatings in Detail

In addition, to be able to be printed like ink, varnish coatings offer the ability to be incorporated with the ink itself, which allows for the visual enhancement of printed materials. Incorporation with ink can be accomplished via two methods: dry trapping and wet trapping.

The dry trapping of varnish occurs when it is printed following the drying of the ink. This is accomplished by sending materials through the system for a second time. Wet trapping is the application of varnish at the same time as other inks are applied.