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.

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