Strong emotions included Part 2
3. The Coatings And The Varnishes
They are liquid finishing materials containing resin which dries to a durable transparent film. Most of them are a blend of resin, drying oil, drier and volatile solvent. One of the main differences between these two types of finishing is the way they are applied. Combinations of different types of coatings and varnishes can give premium results. Then, imagination is the limit. The prepress operator must be careful with traps, overprints and printing range of both of them while co-participate. Due to their viscosity, they have the tendency to spread and thin elements in spot applications may print wrongly.
Coatings are often used as a protective barrier against scuffing of inks. They are applied by flooding the sheet from the coating unit on the press. A glossy coating makes the images pop, but also serves as a barrier against fingerprints, smudges and scratches or damages during mailing stream.
Coatings usually are applied on entire area (flood application), but also, onto selected areas of the artwork (spot applications). Coating is in three parts and will be explained below.
1- Aqueous are water-based coatings. They give a maximum environmental friendliness and offer some extra protection. Gloss, satin and matte finishes are available.
2- UV coatings dry instantly under UV lamps and enhance the appearance of the print, especially gloss UV coatings. It may crack when folded, so one may consider other options too. Aside from the time savings, the eye-catching raised UV applications where fluids are applied in thicknesses as haptical option, stands in high relief. This technique may create unique tactile textures (see also topics 3.Tactiles). UV coatings come in gloss, satin and matte finishes.
3- Soft touch comes in both aqueous and UV, offering a touchable velvet feeling. It is resistant to fingerprints while providing a feel of luxury. Also, soft touch can be enhanced by adding more embellishing applications.
Varnishes While looking for a special effect, but also offering some protection from scuffing, one can consider varnishes. Not only will add that special something to the appearance but is also possible to create some fascinating effects, using spot varnish to make elements pop off.
Varnishes are applied like ink, meaning that the printer will make a plate for it. They come in Conventional and UV formulas and each type is found in satin, matte, semi matte and gloss versions.
4. Spot UV Screen
Screen printing is the century-old technique in which ink gets transferred to a surface to achieve a specific design. The screen is usually made of fine but strong silk gauze (available in different mesh sizes) but can also be made of synthetic gauzes (nylon, tergal) or of wire gauze (phosphor bronze, stainless steel, nickel) or of combinations (nylon–copper, nylon–bronze).
To ensure accuracy, the emulsion gets infused into a mesh screen, forming a stencil that blocks ink from reaching areas outside the design.
The stiffness of the material and the thickness of the fiber are crucial for the correct printing of the artwork. Generally, mesh counts ranging from 25 to 305 are ideal. Mesh count is the number of openings within an inch in any direction; a 305 mesh screen is much finer than a 25.
Regardless of the screening material, the mesh count depends on the level of detail of the design. Both varnish and ink printing are possible with this method; the formula affects the mesh count selection.
A minimum thickness of letter, line or element size of 0.15 mm with a distance between two points 0.25 - 0.30 mm is required. Bleeding is possible and when the silkscreen artwork is bleeding along the step run length, the gap must be at least 5 mm.
Low Tactile screen It looks like an embossed varnish permitting the artwork pop to an appealing result. The screen is also made of fine and strong gauze. The minimum font, line or element size is 0.40 mm with the between distance at least 0.30 mm. Bleeding artwork may damage the cutting blades sooner than usual.
Also, the more porous the substrate is, the need of TTR varnish (Thermal Transfer Ribbon) on substrate becomes essential. Still, when the silkscreen artwork is bleeding along the step run length, gaps must be at least 5 mm.
High Tactile screen It is mainly applied to danger signs and Braille offering a 3D touchable result, specifically on labels and flexo printing applications. Minimum font, line or element size has to be 2.40 mm, while artwork is not possible to bleed, since the cutting around area allow water and air penetration.
A very important point: Due to the high relief, the construction of a taller blade cutter is necessary in order not to damage the surface of the elevated artwork during cutting process.
5. The Die Cutting
Decorative shapes, intricate designs or brilliant cut outs can offer unique experience, while certain pieces are made out of a paper or other substrates. Traditionally, die cutting is achieved by creating die plates pressed onto substrate. Digital die cutting can easily produce pieces like pattern, complex shapes or just a simple label or a box, while a laser beam cuts out the desired shape, working from a special layer added to the design file. The benefits of digital die cutting include the intricacy of the patterns, the elimination of time and cost of producing dies and plates; short runs become more cost effective.
Birch is the common material for most die cutting boards: a channel is laser cut into the wood surface by a laser CAD plotter. Once the pattern is cut, the board is ready to receive the knives and crease rules, which are installed by hand with a rubber mallet. Cutting boards can be re-tooled when their knives become dull or worn, if the surface is still intact and the board in good condition.
Flexible rotary dies are made of thin sheets of steel, which contain the edges for cutting, wrapped around a base magnetic cylinder. They are suitable for low pressure and shallow or partial cutting. The cutting thin sheet can be replaced depending on the part to be cut.
Steel is the preferred material for the blades due to its strength, relatively low cost and availability.
The called “Kiss Cut” is performed when the cut piece has to stay onto the support material, while the cut goes just deep enough to penetrate the top surface leaving the backer intact and operates to adhesive labels.
Stripper units work by complementing die cutters which are located behind the cutting plates; the female and male plates hold the blanks in place eject messy scrap and collect the waste.
This procedure may be creative, but still extra cost effective and sometimes (mainly in flexo) for rotary printing and adhesive labeling, the work must be done manually, so one has to be very careful of the necessity of this option.
The prepress operator must always keep in mind that the artwork follows the final die cut shape, so he needs to be sure that he has the right, final digital die cut while processing the file for bleeding, comfort areas, display windows, gaps, etc. Uncountable creative cutting possibilities can be the creator’s asset.
