Are You Using the Varnishing Techniques Correctly? These Points for Attention Must be Known!
A label is a kind of printed matter used to identify product-related instructions. By sticking it on the outside of the product packaging, we can not only inform consumers of the product name conspicuously, but also make the product effectively differentiated from other similar products, highlighting the brand.In order to further attract consumers' attention, in addition to designing novel product packaging shapes, we can also adopt varnishing technology on the basis of rich printing colors to make the labels brighter and give consumers a refreshing feeling. Varnishing technology refers to the application of a colorless and transparent gloss on the surface of a label, the purpose of which is to increase the gloss of the printed surface and to play the role of anti-staining, moisture, and protection of graphics.In general, the varnishing process can be divided into flood varnishing, spot varnishing, reverse varnishing and so on. In this article, I will mainly elaborate on the above three varnishing processes so that you can better understand their characteristics and points for attention.
PART1 Flood Varnishing
01Characteristics of flood varnishing
Flood varnishing refers to coating the entire label surface with a layer of colorless and transparent varnish. After leveling, drying, calendering, and curing, a thin and uniform transparent layer is formed on the label surface, which enhances the smoothness of the surface and adds modification to printed graphics and texts.
It should be noted that there is a certain difference between the flood varnishing and laminating. Laminating refers to the process of covering the surface of the printed label with a layer of transparent plastic film of 0.012~0.02mm thickness by heating or pressure of the laminating machine so that the label and the plastic film are covered together.
Figure 1 shows the precoating material that needs to be heated for cladding, and Figure 2 is the film material requiring pressure cladding.
Since the laminating process requires the use of plastic film as a raw material, from an environmental perspective, the varnishing process is more environmentally friendly than the laminating process, especially water-based varnishing and UV varnishing.
Water-based varnishing has the characteristics of non-toxic, non-irritating, no organic volatile, low cost, wide source of materials, high transparency and good gloss. Besides, water-based varnish is not easy to turn yellow under long-term strong sunlight exposure, and has strong wear resistance and scratch resistance.
UV varnish contains almost no solvent and requires relatively little energy for curing; it has strong affinity for ink and has strong adhesion; the surface of the printed matter has better wear-resistance, drug-resistance, chemical-resistance and better stability, and can be wiped with water and ethanol. UV varnishing products are not easy to stick and can be stacked after curing, saving time for the next process and improving production efficiency.
Fig1 Pre-coated materials requiring heat lamination
Fig2 Film materials requiring pressure lamination
02 Notes on flood varnishing
When using the flood varnishing process to increase the glossiness of labels, in order to achieve the quality of varnishing and ensure normal production operation, the following four aspects must be noted: First, the thickness of varnish should be controlled well. Second, make a good choice of varnish. As there are many types of varnish, when choosing among them, you must choose different varnishes according to different printing materials and different varnishing methods.The third is to control the viscosity and surface tension of the varnish.The viscosity of the varnish will have an impact on its leveling, drying speed, surface gloss, etc. Therefore, it is necessary to adjust the appropriate viscosity of the varnish according to different printing materials. At the same time, it is also necessary to pay attention to the change of the surface tension of the varnish. The surface tension of the varnish should be less than that of the ink layer on the substrate surface, so that the varnish can wet, adhere, and penetrate the label surface better. The fourth is to pay attention to the coordination between varnishing speed, coating amount, pressure and curing equipment power. The relationship between them should be reasonably adjusted according to the wetting and absorption conditions according to different substrate surfaces.
PART2 Spot Varnishing
01 Characteristics of Spot Varnishing
Spot varnishing is to apply varnish to only a certain prominent position on the label to make it brighter, more vivid and more three-dimensional compared to the surrounding graphics and text, thereby creating a unique aesthetic effect.At present, common types of spot varnishing include gloss,matte,snowflakes, frosting, foaming, refraction, wrinkles, etc. Spot varnishing can be applied either after lamination or directly on the printed matters. Nevertheless, in order to better highlight the effect of spot varnishing, this process is still carried out after the printed matter is laminated, and the majority of them are coated with a matte film (accounting for about 65%). Figure 3 shows the spot varnishing effect of the label. It can be seen that the surface of the label with spot varnishing treatment is more textured and three-dimensional, making parts of the label present higher brightness, transparency and wear resistance, bringing a strong visual impact.
Fig3 Display of spot varnishing on labels
02 Notes on Spot Varnishing
Spot varnishing can be achieved by screen printing or flexo printing. The ink layer of screen printing is thicker than that of offset printing, gravure printing and embossed printing, so the varnish effect of screen printing will be more obvious.
However, when using screen printing for spot varnishing, attention should be paid to the following aspects: One is that the formula of UV varnish is different in winter and summer. When using it, you should carefully distinguish the changes in seasons and weather temperature, and choose the appropriate varnish accordingly. Usually, the curing content of the winter UV varnish formula is lower than that of the summer formula. If the winter UV varnish formula is used in the summer, it will lead to incomplete curing of the UV varnish and easy to cause problems such as anti adhesion. On the contrary, if the formula of summer UV varnish is used in winter, it will lead to poor leveling of UV varnish, causing problems such as foaming and peeling.The other is to stir the UV varnish thoroughly before use. UV varnish is made from a mixture of many chemical raw materials, if it is left unused for a long time, some of the raw materials in the barrel will be separated, so make sure it is stirred thoroughly and evenly before use.
PART3 Pro-cure varnishing
01 Characteristics of Pro-cure varnishing
Pro-cure varnishing is a combination of spot varnishing and spot frosting to achieve high contrast effects in partial graphics and text.The pro-cure varnishing process can be completed in a single pass on a printing machine or offline. varnishing can present a contrasting effect of specular highlights and matte pits on the label surface, creating a stronger contrast in brightness and achieving better results in varnishing. It can play a role in both anti-counterfeiting and aesthetics.
Pro-cure varnishing is that,the non-glossy areas of the design are first printed with a transparent matte base coat by offset printing, then the surface coat is applied to the label in full page and then cured and dried.The surface oil reacts with the base oil printed first to form a frosted matte layer in non-high-gloss areas, while the areas without base oil form a high-gloss layer.Since the non-high-gloss parts adopts offset printing, the overprinting process can be very accurate, which ensures the printing accuracy of the graphics and text in the highlighted parts.
Figures 4 and 5 show label products adopted the pro-cure varnishing process. Among them, Figure 4(b) shows the partial enlargement effect of the label, and the bright part and the frosted matte part are marked in the illustration. The red printed part in the label in Figure 5 has a glossy effect, while the white and blue parts have a frosted matte effect.
(a)
Fig4(b) Label products of pro-cure varnishing
Fig5 Label products of pro-cure varnishing
02 Notes on pro-cure varnishing
When adopting reverse polishing process, please note: Firstly, it is necessary to ensure that the ink used for conventional graphics and text printing has been thoroughly dried or cured. If the ink layer is not dry enough, it will cause incomplete curing of the varnish and poor contrast effect; secondly, do not choose small characters or patterns for pro-cure varnishing effects when designing. If the characters or patterns are too small, it can cause paste problems; thirdly, the thickness of the matte texture is related to factors such as the speed and pressure of the printing machine, varnish thickness, varnish type, and the smoothness of the substrate surface. If the printing machine has fast printing speed, thin oil layer, rough matte texture, and the surface smoothness of the printing material is good, the effect of matte texture can be very obvious. Overall, pro-cure varnishing can achieve contrast effects that ordinary varnishing cannot achieve, which makes the printing effect more exquisite, playing a finishing touch, and improving the quality of label printing.
Nowadays, manufacturers are facing increasingly strict national requirements for environmental protection and pollution prevention, as well as consumers' love for the bright and novel appearance of printed products. In today's competitive market, more and more label printing companies have begun to use various post press finishing processes, especially varnishing processes, on labels. Through small changes in the post-printing process, we can promote the diversification of product design to adapt to the new environment, meet new needs, and add stronger visual impact to label products.
