Print Production

Contents Rotary Printing Other Print Methods Colour Half Tones Tints Overprinting Knockouts Stock Varnishing Foil Blocking

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Print Methods Rotary Printing Rotary printing categorizes the methods to printing which involve wrapping printing plates around a cylinder. There are 3 examples of this: Offset Lithography, Rotogravure and Flexography.

Offset Lithography His makes use of etched aluminium plates. Ink is transferred to an “offset� rubber blanket roller and then onto the substrate.

The stock can be web or sheet fed.

The web offset machines work at high speeds and often have finishing and folding built into it.

Note: Offset = transfer

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1. Paper 2. Impression cylinder 3. Dampening system 4. Inking system 5. Print plate cylinder 6. Rubber cylinder

Rotogravure The plates used for rotogravure are made from copper and hold the mirror image. They transfer the ink straight onto the desired surface. The plates for this process are much more durable and are therefore ideal for newspapers and magazines.

1. Paper 2. Counterpressure cylinder 3. Printing plate 4. Inking roller 5. Ink 6. Doctor blade

Flexography A positive mirror image rubber polymer plate transfers sticky ink onto a surface. The sticky ink used makes it a suitable process for carrier bags, wrappers, labels etc.

1. Paper 2. Counterpressure cylinder 3. Printing plate 4. Inking system

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Other Print Methods Digital Print This is the reproduction of digital images onto a surface by using a device that translates digital code, without the need for an intermediate physical process. This method is suitable for short or special runs.

Pad Printing This method allows for transfer of a 2D image to a 3D object. The image is transferred from the printing plate via a silicone pad onto the substrate.

Example of digital print

Screen Printing A screen is made using woven mesh, followed my a stencil becoming exposed onto the screen. The ink is then forced through the stencil. This method of printing is not suitable for high volume printing, as each colour has to apply before applying the next. If you are planning to screen printing Example of pad printing a full colour image, the image should be split into the 4 channels. This means that 4 screens will need to be exposed.

Opposite: Example of colour channels 4

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RGB

CMYK

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Colour Print uses a colour mode referred to as CMYK (Cyan, Magenta, Yellow, Key). This is known as a subtractive colour system, as opposed to projected colour – which is additive colour (RGB).

One way to remember these names is: Subtractive – Substrate Additive – Add to make white Theoretically all visible colours can be formed with the additive primary colours, this can’t be said for CMYK. However spot colours can be produced using process colour to print colours that can’t be mixed. For example, fluorescents, golds and silver To find out whether the colours in your design can be printed software such as Photoshop offer a gamut warning feature, that will indicate any colours unprintable through CMYK.

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Halftones Halftones are images made up of dots, which collectively replicate the continuous tone of a photograph.

The dot’s can be different in shape, size, spacing and angle depending on which effect you want. Varying the size or spacing of the dots has a direct influence on image brightness.

When printing halftone a series of screens will be used to print each colour, gaining the photographic tone. Otherwise each of the dots will just be printed on top of each other.

Tints By adding white to a colour, tints can be created. This means that lots of different tones can be created using just one colour. This is a particularly useful technique for one, two or three colour jobs.

Another way to add an extra colour without using ink is to use coloured stock.

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cyan 105 yellow 90 magenta 75 black 45

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Over Printing Overprinting refers to when an ink is printed on top of another ink. A colour can only be overprinted if it’s already printed.

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Knockouts A knockout is the purposefully blank area on a layer, left so that the layer overlapping it can fill in the gap. This can cause flashes however, which are unprinted white areas.

Reasons for flashes occurring include; incorrect adjustment of the press or perhaps the shape of the paper changing during printing. You can reduce the risk of these by overprinting/overlapping areas of colour by 3mm (standard). This is known as ink trapping.

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Stock Several considerations should be taken when choosing a stock; to ensure it will support the design, whether you have a budget to work to and it’s GSM (and how this will affect postage costs).

Colour reproduction will differ depending on what stocks are chosen, when working on a project it is likely that the designs will be printed on a number of stocks and perhaps a colour palette suitable for this should be decided on.

The GSM (gram per square meter) can give an indication of how thick or stiff stock is. This can have a direct affect on how successful folding mechanics are. Sometimes thicker card or board is measured in a different unit – microns. A micron is 1000th of a millimetre.

A coated stock has an improved surface smoothness, gloss, whiteness and printability. Resulting in brighter and sharper images. Coated stocks are typically used for brochures, leaflets and posters.

An uncoated stock is much more absorbent and is likely to be used for business stationery.

As well as the usual A sizes, printers also use SRA sizes. These are slightly larger versions of the original A sizes, allowing for trimming, grip and bleeds.

An example of this would be: A0 – 841x1189 SRA0- 900x1280 Opposite is an example of two stocks that have been bonded together, so that their are different colours and texture. This is called duplexing.

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Finishing Once printed there are a number of finishes available to apply to a design. These finishing techniques can be toh decorative nd functional.

Varnishing This takes place in the last printing stage.

It is the application of a colourless, glossy or matt, drying layer of varnish. Applying varnish will alter the original texture of the stock and has the ability to change the hue of the printing ink. It also speeds up the drying process.

Spot varnishing refers to varnishing that happens in just a particular area and is treated like a separate colour.

The varnish can be applied “wet” or “dry”.

By wet, this means a wet layer of varnish is

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applied onto a wet layer of ink, therefore they both absorb into the stock at the same time. This will reduce the impact of the varnish effect.

Dry refers to applying the varnish layer once the printed ink has dried.

Also note that, varnish performs better on a coated surface.

Once printed there are a number of finishing techniques available to apply to a design. These finishing techniques can be both decorative and functional.

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Foil Blocking Hot foil stamping is useful for applying colour that may not be available through printing methods such as digital printing, such as metallic colours. The foil is originally on a polyester film and is applied to a stock through heat and pressure. The foil will stick to the stock depending on where the glue is – usually transferred through a stencil.

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