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The method calls for the printing press to be supplemented with a relief aggregate and a heater. After the normal printing process a chemical powder is sprayed over the ink on the sheet. The sheet then goes into the heater where the ink and powder melt together and swell up into a relief. This then dries and hardens.
The process is also called thermographic printing and all PMS colours can be used. Relief printing is most suitable for thin lines and texts. It is not possible, however, to emboss or foil block over relief print. Nor is it possible to relief print over foil blocking. |
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The process of creating differences in the level of the paper’s surface – known as reliefs – with depressed and raised areas is called embossing. The pattern is created in an embossing machine using stereotypes or embossing plates.
There are basically two different kinds of embossing: positive and negative. Positive embossing involves raising a section up out of the paper, while negative entails depressing a section. Moreover, sculpted embossing can be used to create several different levels. This method is the most advanced, and can only be achieved using embossing plates. When ordering embossing plates, it is particularly important that the paper has been selected and to be extremely clear about the desired effects.
Paper grade is a vital factor in embossing. As a general rule, the thicker and softer the paper the better the results.
i The strength of the paper is also significant, and woodfree grades are generally recommended as they have better bursting resistance. To avoid bursting, it is also important to use the right pressure when embossing.
Careful testing – on the right paper – is essential when embossing, and a good working relationship should be established with the engraver and printer before the actual embossing phase. |
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There is another kind of lamination which differs to that described in the section above, and it refers to glueing together several sheets to produce a single thicker one. For example, two 150 g/m² sheets can be joined to form a sheet weighing just over 300 g/m² (the glue also weighs a few grams).
The laminated sheet can be made of various materials such as liner, cover paper, plastic film or metal foil.
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Foil blocking involves adding a thin layer of foil to the paper with the aid of heat and pressure. The foil is usually made of gold or silver, although there are also mother-of-pearl and structured versions. If more than one foil is being used they should not be overlapped, and the ink must have dried properly before foil blocking begins, otherwise the print will not adhere correctly. One tip is also to avoid using too much spray powder when printing.
In the context of foil blocking, another term sometimes heard is foil embossing – i.e. embossing the paper at the same time as foil blocking. There is also a new type of foil blocking where different amounts of pigment are used, called tint foil blocking. |
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i = ARCTIC PAPER RECOMMENDS
Together with laminating, varnishing is the most common method of surface-treating a paper. There are several varnishing methods, the most common being spot UV varnishing in a screen press, full varnishing and protective varnishing direct in the printing press.
i Uncoated paper grades are excellent for varnishing, although it is important to bear in mind that the effects will be slightly different to those seen on coated paper.
Since fully varnishing the sheet is rarely a complete success, spot UV varnishing is to be preferred. This entails varnishing selected parts of the paper, such as an image or logo. Very special, exciting results can be created using spot UV varnishing on uncoated paper.
When spot varnishing an uncoated paper it is essential to first prime the sheet and then varnish once, or in some cases twice, for the perfect result.
Also bear in mind that folding after varnishing may cause problems. Varnish is hard and not as flexible as laminate, so the outer layer may crack when the paper is folded. This can be avoided by scoring the paper where the fold is to be.
i A sheet of paper can also be varnished in the printing press using the press varnish method. The difference here is that no gloss effect is achieved – the varnish is absorbed into the paper – instead the varnish primarily serves as a protective function against dirt, dust, and wear. The method is therefore often called protective varnishing. See the examples in the Effect section! |
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Laminating involves applying a thin coat of plastic film or foil to the paper’s surface. The method works well with uncoated paper and is used in the same way as varnishing for greater protection against dirt and wear, as well as giving increased folding strength.
Laminating the paper also produces a different surface finish compared to varnishing. This partly depends on which laminate you use, for example there are matt, gloss or patterned laminates. It also depends on the roughness of the paper.
i For optimum laminating results on uncoated paper, select a grade with low roughness, since a rough paper surface makes it harder for the film to adhere, and may produce a slightly milky, greyish appearance especially when laminating dark surfaces.
Just as with varnishing, it is important to use a minimum of spray powder in the printing process, as this too can result in reduced adhesion and detract from the appearance.
There are two kinds of laminate: pre-sized laminates, and those which are sized during the laminating process. The non pre-sized laminates are generally preferable when working with uncoated paper. There is however an exception, i.e. when laminating digitally printed matter. Owing to the fact that inks in a digital press contain toner and silicon, it is difficult for the laminate to adhere properly. In this case, use pre-sized laminate and a high temperature.
i Speaking of high temperatures, bear in mind that paper alters with changes in temperature and atmospheric humidity, yet a plastic laminate does not. In other words, laminating a sheet of paper before the ink has dried or if it is subject to abnormal moisture can cause problems. |
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