The Ultimate Drip-off/UV/hybrid/TWIN Coating Effect Tutorial
In our third tutorial we would like to take a closer look at one of our favourite coating effects. We are talking about so-called Drip-off/UV/hybrid/TWIN coating effects, which offer an enormous range of possibilities at a moderate cost if the job is planned correctly and implemented with printing alchemy.
Let's start with a general description of the effect, or rather the effects, because today there are indeed many variants and, based on this, many possible application processes and effect variations that can be created using this technology.
This coating enhancement, which first became known as drip-off technology, was actually developed on the basis of the realisation that oil-based and water-based coatings do not harmonise with each other when applied wet-on-wet due to the very different surface tensions and that a push-off behaviour can be observed.
In other words: the oil-based coating applied via a printing unit pushes away the water-based coating applied subsequently via a coating unit. If the print image of the oil-based varnish is quite small, the water-based coating is then displaced onto the surrounding areas in the subject that are free of oil-based varnish. After the drying process, the oil-based and water-based varnishes lie side by side on the printed sheet. However, if the area of the oil-based varnish is too large to completely displace the water-based varnish, a kind of orange peel appears on the areas where the oil-based and water-based varnishes are applied on top of each other.
This effect was then exploited and the two varnishes were adjusted to each other in such a way that the "orange peel" was as fine as possible, which can be perceived by the eye as well as tactilely as a matting and which is reminiscent of the micro-folding that is known today mainly from excimer processes.
The drip-off effect was born and its technology was further developed.
Very quickly, manufacturers created different combinations of oil-based and water-based varnishes to make the degree of matting controllable. The best-known applications today are gloss/structure and matt/gloss effects. But here, too, development did not stop for a long time. In the years that followed, these coating effects were further developed for combinations of oil-based and UV lacquers. Then came pure UV-based coating systems - better known today as hybrid coating systems - onto the market in which it was possible to dispense completely with the use of oil-based varnishes, and later still hybrid coating systems based entirely on UV-LED technology.
What they all have in common is that a print varnish component is always combined with a coating unit component. This means that only one conventional printing plate is actually needed to produce the coating effect. In most cases - especially in commercial printing - the use of a coating plate can be dispensed with completely, which greatly reduces the production costs for implementing these lacquer effects. What's more, thanks to the printing plate used to create the effects, incredibly filigree coating effects can also be achieved, and the accuracy of the register of these coating effects, produced inline, is enormously high, because the printing varnish can be set just as precisely via the machine register as a conventional printing ink. There is no need to worry about squeeze margins or peel-off coefficients as with conventional coating effects applied via flexo or chambered doctor blade systems, there is no need to worry about the coating plate running in or the subject buckling in the case of designs that are too filigree, and you can even play with half-tones in the effect design. Even overfilling or underfilling the coating effect is usually unnecessary because of the extremely high register.
It is not without reason that this coating effect is one of the most popular coating effects on the market.
Obviously, the implementation of these effects requires quite a broad knowledge of effect planning as well as design, prepress, print production and finishing. Reason enough for us to write this comprehensive tutorial and share our experience of more than 35 years.
When planning these effects, the first thing to consider is which coating technologies are suitable for the particular application. The systems and their advantages and disadvantages are too different to simply use them as one pleases.
So let's start with a rough list of the different technologies:
Oil-based print varnish / Water-based coating
As already described, this combination is the great-grandmother of all drip-off effect coatings. The big advantage of this combination is that it can be applied on almost any press with an inline coating unit. The disadvantage is that with this combination the effect itself is the least eye-catching, both visually and tactilely. In addition, the final printed products unfortunately tend to yellow considerably due to the oil-based varnish used. In order to create the strongest possible visual contrast with this combination and to counteract the yellowing, the effect should only be used on dark to black areas of the printed image. However, the use of water-based varnish does not generally pose any problems in the finishing of these printed products. A typical example of this coating combination is SENOLITH® OB MATT VARNISH TWIN FP 355419 as a printing unit varnish together with SENOLITH® WB HIGH GLOSS COATING TWIN FP 350630, both from WEILBURGER Graphics.
Oil-based print varnish / UV lacquer
This combination is of course only suitable for printing systems with UV equipment. But here, too, the oil-based varnish component is the main problem and even with this combination, severe yellowing due to the oil-based varnish is to be expected. So for this combination, too, the advice is to use this varnish effect only on dark to black areas of the print image. However, with this combination, if applied correctly, the varnish effect is more pronounced both visually and tactilely. However, because of the UV lacquer used, the usual problems associated with UV printing, such as breakage and flaking of the lacquer during cutting, die-cutting, folding, creasing, stitching, etc., must be expected during finishing, especially if the lacquer is applied at the edges. For this reason we recommend using a coating plate also for commercial printing and omitting the UV lacquer in all vulnerable areas. This increases production costs, but in the end, it saves waste and complaints in most cases. An exemplary coating system here is SENOLITH® OB EFFECT MATT VARNISH HYBRID FP 355424 with the embossable SENOLITH® UV GLOSS LACQUER INLINE STAMPABLE FP PLUS 360435 from WEILBURGER Graphics. The enormous advantages of embossable coatings will be explained in detail later.
UV print lacquer / UV lacquer
This is currently our favourite combination, because by omitting the oil-based varnish and using a UV print lacquer in its place, the risk of yellowing is almost completely eliminated and this effect can therefore also be used on bright and pure white areas of the print job. The effect is also visually and tactilely more intense than with the varnish combination oil print/UV varnish, which allows beautiful, filigree and striking varnish effects even on unprinted substrates. However, here, too, great care must be taken, especially in finishing, and here, too, the use of both UV lacquers is likely to cause problems that can be avoided by using a coating plate and omitting endangered areas such as cut and fold lines, creasing, embossing, etc. in advance during print preparation. A typical system we often use is SENOLITH® UV OFFSET GLOSS LACQUER HYBRID 369402 together with SENOLITH® UV GLOSS LACQUER HYBRID 360053 from WEILBURGER Graphics.
LED UV print varnish / LED UV lacquer
Not least for reasons of resource-saving and energy-saving print production, LED-UV printing is currently an increasingly popular printing technology and even for these printing systems based purely on LED-UV curing, appropriate solutions for implementing these Drip-off/UV/hybrid/TWIN coating effects are already available today. In fact, the maximum effect strength and detail that can be achieved is among the highest of all the coating systems discussed here. But on the one hand there are still very few printing systems on the market that can operate in pure LED UV mode – to our knowledge there is currently not one in the packaging industry – and on the other hand all LED UV coatings and ink systems unfortunately still have a tendency to yellowing due to the necessary use of narrow-band photoinitiators. Not as strong as oil-based varnishes, but still visible. In addition, the energy-saving potential in LED-UV printing depends very much on the maskability of the print subject and is often only marginal compared to systems with conventional UV lamp systems for print jobs that have a high area coverage and thus often cannot be masked at all. In return, however, the printer then buys back the tendency to yellowing for expensive money by upgrading the press. For this reason, we are currently not a great fan of LED UV printing, but we are happy to await technological developments in this area – especially with regard to the photoinitiators used – and are eager to see what is still to come. An exemplary system here is SENOLITH® UV OFFSET MATT LACQUER LED HYBRID 369868 as the printing component with SENOLITH® UV GLOSS LACQUER LED HYBRID 360754 as the coating unit component from the WEILBURGER Graphics GmbH.
While we are on the subject of photoinitiators, the question of the use of these coating effects in food packaging must of course be addressed. Basically, we are not aware of any Drip-off/UV/hybrid/TWIN coating system that is approved for direct food contact. This is because all these systems use either an oil-based print varnish or UV-curing lacquers. However, the first question that arises here is why one would want to use such a coating effect in direct food contact at all, since effect coatings are normally used on the outside of mostly secondary packaging. And for this purpose there are now various Drip-off/UV/hybrid/TWIN coating systems that have been approved for indirect food contact. Some of them are even based on self-crosslinking coatings such as SENOLITH® UV GLOSS LACQUER INLINE FP NDC PLUS 360435 in combination with SENOLITH® OB EFFEKT MATT VARNISH HYBRID FP NDC 355424, again both from WEILBURGER Graphics.
What does this mean for the planning process?
Well, if you are free to choose a suitable coating system and thus a printer, you should opt for a UV-based coating system if possible, in order to achieve the strongest possible coating effect. If the varnish effect must be produced on light-coloured or even unprinted areas, we believe that only UV/UV hybrid varnish systems are suitable.
Regardless of which system is chosen, these effects are always most effective on dark or black printed areas. All systems are available in matt/gloss and structure/gloss combinations, although we work almost exclusively with structure/gloss systems because the microstructure they produce makes the effect more striking and there is no clouding of dark print areas as is usual with matt coatings. If these coating effects are to be used in food packaging, it is essential to ensure that the coatings, inks, auxiliaries and substrates used, and not least the printing company commissioned, are food-certified. To the best of our knowledge, direct contact with foodstuffs is not possible at the present time.
The design process
Of course, one must also know how such coating effects are incorporated in the design process, what technical limits must be observed and what all must be considered to be able to count on an optimal result at the end of the process chain.
Let's start with the question of how such a varnish effect is created and applied in Adobe Illustrator, InDesign or even Photoshop, for example.
The print varnish
Basically, the varnish effect consists of a single spot colour form. It is important to note that all the drawing elements of this form (i.e. solid/black and all halftones) end up with a more or less pronounced matt or textured tone and all the non-drawing elements (i.e. white or 0 % area coverage) will then appear glossy. Thus, this form of coating is more or less a negative of the gloss form of coating. Depending on the system used, intermediate tones may also be noticeable in the final result in the form of different matt tones. Especially when using a metallised substrate or a cold foil application, it is even possible to influence the gloss level of the metallisation in a very filigree way. But more about that later.
So we create a spot colour form in Illustrator and call it simply print varnish so that the prepress department can clearly assign it later. We can now design this print varnish spot colour in exactly the same way as we know it from conventional spot colour forms. Even the use of bitmaps coloured in this spot colour form is possible, but here too we must always keep in mind that drawing elements will appear matt at the end. Therefore, when using coloured imagery, a prior conversion to a negative has proved useful. This is because our brain tends to perceive glossy forms negatively. In a portrait, for example, shiny eyes and teeth are later more realistic than matt ones. Of course, there are exceptions here too and you have to try to assemble the later print image as well as possible in your head, unless you have a visualisation possibility to do so. But we will also illustrate this topic in one of our following tutorials.
Here and now we simply need some experience and a little imagination to realise this varnish effect.
What has become very popular in recent years are filigree patterns in the implementation of these Drip-off/UV/hybrid/TWIN lacquer effects. Here, the attempt is made to use the special reflective behaviour of these lacquers to create a kind of tilt or relief effect by designing fine, mostly homogeneous patterns in the lacquer effect. Correctly implemented, this can produce very striking coating effects that can almost be described as 3D effects. By tilting and rotating the printed sheet, they then create light reflection patterns reminiscent of lenticular printing or Fresnel lenses.
We would therefore also like to explain the design of these effects here, as they require an optimal interplay of print data, print forms, application process and finishing.
By the way, these patterns are best used in the structure/gloss systems. The effect when using the matt/gloss systems, on the other hand, is difficult to see.
To create these pattern effects, Illustrator offers various powerful tools. On the one hand, there is the matching tool, with the help of which line patterns in particular can be created very well, easily and precisely, and on the other hand, there is the pattern generator, with which patterns without a rapport in particular can be created.
All design elements created in this way are based on a design guideline that has emerged from practice and years of experimentation:
Both the positive and negative line thickness of 0.25 mm should not be undercut here, measured against the unscaled final print data.
This is because these coating effects are based on the displacement principle and the cohesive and adhesive forces of the two coatings against each other must not be exceeded so that the effect does not run.
To visualise this, simply imagine a glass that is filled slightly over the rim with water. Based on the surface tension of the water, this creates a lenticular bulge of water beyond the rim of the glass. If we continue to fill the glass with water, we will eventually exceed the equilibrium of surface tension and density/mass and the water will spill over the edge of the glass. This is pretty much the principle we have to follow when creating these paint effects. And if we want to avoid the effect leaking into the print run already at the design stage – assuming an optimal application process in the subsequent print production – it is better not to go below this 0.25 mm, either positively or negatively.
Attention: Especially when using very filigree design patterns in the form of vectors, very large work files of several gigabytes can be created, which quickly push smaller workstations or older rips to their performance limits. Even our M1 Max workstations, which are usually equipped with 64 GB RAM and are currently among the most powerful on the market, are sometimes brought to their knees with some designs. Here you have to check whether it makes sense to optimise the vectors before writing the print PDF or to convert them into a high-resolution bitmap (1200 - 1600 dpi). Output in PDF/X3 or even PDF/X4 format is also recommended here, provided the print shop already supports this, as most computers often can no longer process these data volumes when reducing transparency in PDF formats under PDF/X3.
As soon as we have finished designing the print varnish form, we can take care of the coating unit form.
The coating unit component
As described above, we do not really need a coating form, especially in commercial printing. A blanket for full-surface application of the gloss coating is very often sufficient here. But when UV-based coating systems are used, or especially in packaging printing where glue flaps have to be kept free of coating, a coating form or at least a stripped or plotted blanket is indispensable and it makes sense to create such a coating form at the same time.
The principle is again the same: We create another spot colour form and call it a coating unit component or simply gloss coating for clear assignment in the pre-press stage. We then set all the elements that are to be coated to black or solid, and all the areas that are not to be coated to white. Since a coating plate must be produced at the end to apply this form, halftones are prohibited when designing this form. So a pure stroke conversion is required.
To ensure that the Drip-off/UV/hybrid/TWIN effect works in the end, we have to make sure that all areas where the print varnish is applied are also coated with the gloss coating of this form. Certain areas of the print image can be designed without the gloss coating, but the application of a printing unit varnish alone will result in a very faint (gloss) coating effect in these areas (yes, the printing unit coating is usually a gloss coating, too, and it is only in combination with the second gloss coating applied over the coating unit that it will later appear matt). When using UV lacquer systems we now leave out all the areas at risk, such as cutting lines, die-cutting lines, folding lines, creasing lines, embossing, hot stamping (unless an overprintable UV lacquer is used), by approx. 2 - 3 mm. The 2 - 3 mm are again an empirical value from practice and depend on the register accuracy of the printing company commissioned. If the pre-press, printing and finishing processes are optimally coordinated, a gap of 1 mm may be sufficient, which means that the lacquer cut at these points is less noticeable on the printed product later on.
Tip: Stampable UV lacquers
At this point a word about stampable UV lacquers such as WEILBURGER Graphics' SENOLITH® UV GLOSS LACQUER INLINE STAMPABLE FP PLUS 360435: for reasons of production reliability and quality, it makes sense to use stampable lacquers such as SENOLITH® UV GLOSS LACQUER INLINE STAMPABLE FP PLUS 360435, especially for high-finish print jobs where hot stamping is planned in addition to a Drip-off/UV/hybrid/TWIN effect coating. This saves the overfilling of the print image and varnish under the hot embossing and thus enormously increases process reliability, precision and thus the quality of the final print products. This also makes it possible to produce very filigree hot stamps without visible tear-off edges and flashing of the print image, lacquer and hot stamping. Stronger substrate shrinkage can also be absorbed much better during the embossing process than would be possible with recessed printing sheets. The stampability of these coatings is nowadays enormous and comparable to hot stamping directly on the substrate. However, when using stampable coatings it is essential to remember that the Tesa test, which is still very popular in the printing industry, should not be used here. The reason for this is the deliberately low surface tension of these coatings, which are designed to establish as firm a bond as possible with the adhesives applied. It is therefore only logical that a rubbed-on Tesa strip will also adhere very strongly and quickly to the lacquer surface and that the Tesa test will therefore almost always result in a lacquer tear. This means that when stampable coatings are used, the Tesa test says nothing about the application quality, scratch and rub resistance and should be avoided.
Because we want to work as cleanly as possible, we also lay out the lateral guide bars when we make the coating form. We make sure that the bars at the start of printing are tapered to prevent the plate cylinder from swinging during production, and when using several coating forms, we place the bars next to each other rather than on top of each other. We also make sure that the web bevels on the left and right of the sheet face outwards, i.e. that they are mirror images of each other, to prevent the sheet from being skewed in the press due to frictional forces.
We also add sheet labelling, mark the infeed, set measuring marks for perfecting register and register marks. If necessary, we add ink take-off areas if the area coverage of the printing inks or the print varnish is low. We do not place the print control strip on the sheet because this is very printer-specific and each printer uses its own control strip according to the colour management used.
Once we have created all the forms – in packaging printing this also includes cutting, creasing and possibly gluing forms – we export everything in consultation with the printer in the desired PDF standard and with the appropriate colour intent.
Finally, we write a production plan including all the necessary form descriptions and send it all together to the printer.
The printing process
The real magic of this type of finishing takes place in the pressroom, of course. Our forms are now exposed and, in addition to the actual printing plates, we now have a printing plate for the print varnish component exposed and, if necessary, another lacquer plate or a stripped, unstripped or plotted blanket.
Depending on which technology we use, a conventional press or a UV/hybrid press must now be prepared for printing. It is generally recommended that the coating unit be tempered for all systems so that the viscosity of the coating can be kept constant throughout the run. In the case of pure UV, LED and hybrid systems, intermediate dryers are essential so that the image and coating can be cured individually. If sufficient printing units are available, it is advisable to place the varnish component in the last or penultimate printing unit and to leave some space between the inks and the varnish. This increases process stability in the production run.
The coating unit component is usually applied with an anilox roller at between 9 and 18 cm3/m2 , depending on the coating system used, the substrate and the print image in the coating. Why does the print image play a role here? Well, if the printed image in the coating has a very fine pattern with very high area coverage, i.e. it consists of many fine lines over the entire print area, the coating displacement means that less coating is needed on the sheet than, for example, if there are only a few drawing elements in the print varnish. So experience also plays a decisive role here.
Tip: We have already explained in our second tutorial how to determine the area coverage of the print varnish and also the expected varnish consumption with simple tools and an online calculator.
When using this varnish effect, you should always use a substrate that is at least single-coated, preferably double-coated. The implementation of this effect varnish on absorbent substrates has not been possible up to now. On the other hand, it is possible to use this coating effect on films, on Met-PET or on cold foils. More information on this later.
The smearing point
A very important factor in this coating enhancement is the so-called smearing point of the press, i.e. the process area where there is just enough dampening water for ink separation. The best coating effect is achieved when printing at the smearing point, and it is essential to run the press up to the smearing point beforehand, especially if the amount of print varnish has to be increased.
Experience has shown that these coating effects are usually not stable until the production run. This means that the makeready process for these coating effects is heavily dependent on the printer's experience. This is why it is advisable to calculate with a little more makeready sheet for these types of coating effects.
Once the sheet has been set up and the coating effect has been approved, the question arises as to the optimum production speed. The fact that a displacement process must take place to achieve this effect, i.e. the coating applied via the coating unit must be physically displaced by the printing varnish, means that a certain amount of time is needed. Excessively high production speeds are therefore counterproductive when applying this effect coating. But the curing process of inks used purely for UV applications also plays a decisive role here. If the lamp power is too low or the production speed too fast, the inks are not yet sufficiently cured and can thus interfere with the coating effect.
The special case of hybrid inks
Particularly when hybrid inks are used, they can sometimes produce an unwanted coating effect, i.e. displace the gloss coating, because their surface tension is too close to the surface tension of the print coating. In such cases the only option is to change the ink system completely and replace it with UV inks.
Use on metallised substrates
As already mentioned, these Drip-off/UV/hybrid/TWIN coating effects can also be used with metallised substrates, Met-PET and cold-foil finishes such as Univacco Holland BV's Cold Transfer-Sheet-fed Offset-Metallic-CF6.2S. Thanks to the possibility of working with half-tones and even gradients in the print varnish, even the gloss of the metallisation can be controlled homogeneously. From experience, however, we recommend using only structure/gloss varnish systems for such combinations. This is because these structure/gloss systems create a kind of microlens in the coating that changes the angle of incidence and exit of the reflected light, thus doubling the effect, whereas matt/gloss systems usually use matting agents that create an unattractive optical clouding of the metallisation. When combining this coating effect with inline cold foil application, it must be borne in mind that at least 7 printing units and one coating unit are required for implementation in the Euroscale range. The first two printing units for the cold transfer/cold foil application, then four printing units for the colour set and then another printing unit for the print varnish. Since this is too much for most press configurations, the cold foil and the print image are often applied in a separate machine run and the coating effect is then applied in a second pass. Naturally, this results in a lower register accuracy than with purely inline production, which in turn should be compensated for in the pre-press stage by using over/underfilling of the print varnish.
Use on holographic metallisation
From a purely physical point of view, it is of course also possible to use this coating enhancement on holographic metallisations such as the Cold Transfer-Sheet-fed Offset-Holographic-CF5.1 Rainbow from Univacco Holland BV. However, such effect combinations are not advisable because the previously described microlens effect destroys the holographic property of the metallisation in most cases and usually only a milky white result with a slight hint of spectral colour reflection results from such effect combinations. However, a combination of Drip-off/UV/hybrid/TWIN coating and holographic metallisation is still very much possible and, thanks to the striking effect contrasts, can also be implemented very nicely in highly finished print products. However, care should be taken to ensure that the print varnish never lies directly on the holographic metallisation. If there is enough ink on the film or even an opaque white (with MET-PET) or the varnish effect with cold foil finishing is only used in areas without metallisation, these effects can be combined very well and the gloss coating then also serves to protect the metallisation.
Use in combination with effect pigments
It is also theoretically possible to use effect pigments, at least in the coating component. There are even pigments that are fine enough to be applied over the print varnish. However, experience has shown that, especially with high pigment concentrations, the surface tension and flow behaviour of the coating is altered to such an extent that the coating effect is virtually non-existent. We therefore advise that if an effect pigment is to be used in parallel with the Drip-off/UV/hybrid/TWIN coating effect, it should be applied via a second carrier coating and, irrespective of the effect coating form, via a second coating unit or via a second press pass/offline and my use of a second coating plate.
Provided all sources of danger have been eliminated in advance during prepress preparation as described above, there is no need to fear the finishing of print jobs with Drip-off/UV/hybrid/TWIN coating enhancement. All the cutting/punching/folding/creasing lines have already been cut out and all the hot-stamping areas either cut out or, if stampable coatings are used, there is no need to fear them. Nevertheless, there are still a few finishing hazards that we would like to address briefly.
Blind and relief embossing and debossing
Blind and relief embossing/debossing are popular finishing elements, especially in packaging printing. These can, of course, also be used in this coating finishing process, but this should also be taken into account at the production planning stage. For example, if blind or relief embossing is to be used later, especially when UV or LED-UV coating systems are used, stampable coating systems should be used wherever possible. These varnish systems have a higher elasticity even after curing and can therefore be better formed without flaking or cracking. The lamp power should also be set at the lower end for such UV print jobs so that the coatings do not cure too brittly. Since UV inks and UV lacquers also need up to 24 hours after the printing process to cure completely, experience again shows that finishing as soon as possible after printing greatly reduces the risk of coating damage.
If we have used an embossable coating system as described above, we need only select a hot embossing product suitable for UV lacquer, such as Hot Stamping-Metallic-TS-05 from Univacco Holland BV, and need not worry about anything else. Even multi-level relief embossing is possible here in a single operation. In most cases, the production-related shrinkage of the sheet can be compensated for without rims when setting up the embossing process.
If, on the other hand, we have opted for a non-stampable varnish system and knocked-out the printing and varnishing form under the stampings, the same applies here as well: a finishing process as soon as possible after printing is to our advantage. If we wait too long, especially with large embossing clichés, we may not be able to get the sheet cleanly prepared and thus have to live with rims/flashes and the embossing peeling off over the edges of the coating. We therefore recommend weighing up the advantages and disadvantages of stampable coating systems quite early in the planning process and ideally always using the stampable coating system if hot stamping is planned, especially with UV-based coating systems.
The glass plates effect
The glass plates effect, which is particularly common with UV print jobs, can also occur with Drip-off/UV/hybrid/TWIN coating effects, especially if they are applied on both sides. However, this usually only happens if the proportion of print varnish on both sides was very low and therefore large areas of the print sheet were only gloss-coated. This can be remedied by deliberately filling the areas on the sheet between the copies with print varnish and thus matting them, or by deliberately running small piles in such print jobs. If the press is equipped for this, the use of stone powder in such UV jobs can also counteract the glass plates effect.
Marking and blocking can also be an issue, especially with double-sided print jobs with this effect coating. This is particularly the case with oil-based varnish / water-based coating systems on substrates with a high coating and minimal absorbency. Here the blocking resistance of the coating systems should be discussed with the coating supplier before going to press, powder should be used if possible and small piles should also be run.
Particularly with print jobs that are only partially coated with a strong coating effect in the sheet, the strong difference in material thickness in the pile due to the effect can also result in poor flatness. With UV coating systems in particular, a difference in material thickness of 50% can be caused by the coating effect, especially with thin substrates, which produces this poor flatness, which is then amplified in the pile. This causes problems from time to time, especially in the stacking of finishing systems. Here, too, this effect can be counteracted as far as possible by applying the varnish to the edges of the printed sheets during the preparation of the print data. And here, too, it is advisable to run small piles in print production.
Conclusion: The possibilities of Drip-off/UV/hybrid/TWIN coating enhancement are immense and there is hardly any other coating enhancement that is blessed with such a high degree of effect diversity and precision. This type of finishing is now available for virtually all printing systems and application technologies, provided that at least one coating unit is installed inline. It is highly efficient and inexpensive, can be excellently combined with a wide variety of finishing and further processing technologies and is also suitable for food packaging, at least in indirect contact. By skilfully combining design and effect, it is even possible to create finishes that appear almost three-dimensional. However, the use of these coating systems requires a certain amount of experience to produce optimal results – both for the designer of the effects and for the printing company producing them – and we hope that with this comprehensive tutorial we can contribute a little to this effect being used more often. Maybe we can also take away the fear of one or the other printer to simply try out this beautiful varnish effect.
It's worth it. Promised.
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