Strong emotions included Part 3
6. The Embossing & The Debossing
Embossing and debossing create great tactile experience; embossing gives a raised pattern in the substrate, while it works much like die cutting, but the embossing tool presses a pattern or design onto a substrate, rather than cutting it out. Debossing acts contrary, by depressing the image, creating a concave impression.
Recent developments for embossing include digital presses that can handle embossing inline as part of the printing process, reducing time and offering in house full service.
The minimum width of font, line or artwork has to be 0.15 mm. More intensive relief effect is obtained by thickening. From 0.40 mm the embossing becomes more appealing. Prepress operator needs to consider thickness according the artwork and the “eye” of a hollow font, while distances between elements may need to be changed. In between distance can be 0.25 - 0.30 mm.
Substrate’s texture and are important; if the printing material is too much grainy, embossing may be not necessary or high relief may damage it. The depth of pressure is determined by the material, when a thicker material needs a thicker artwork.
For adhesive labels, avoid bleeding of the embossing, since it is not possible to guarantee the peeling off, as moisture may penetrate the label.
The multilevel reliefs obtain bidimensional effect at different levels. One must ask the supplier if it is possible to deliver cliché with those parameters.
Cliché is usually made out of magnesium with common thickness 2mm, 3mm or 7mm, suitable for short to medium runs, but also out of brass, ideal for medium to long runs, with thickness 4mm and 7mm. This option is more expensive, such as copper is, a very durable and perfect material for medium to long runs, intricate detail much better than brass or magnesium, generally comes in 1.63mm, 6.35mm and 7mm. Polymer or nylon (usually 0.94 mm or 1.75 mm) are suitable for applications for letter press.
7. The Foiling
Foiling adds metallic finishing to a printed piece. Elements of luxury, glamour, sophistication and a certain blinky effect are eye caching. Traditional foiling is done with hot or cold stamping. Hot stamping uses a stamping tool and heat to apply the foil to selected areas, while cold stamping uses cliché and glue.
Hot Foiling In the very first manuscripts they used real gold leaf for decoration, while thin layers of gold were brushed onto specific items (frames, statues, furniture, book covers).
In the 18th and 19th centuries, after printing presses became widely used in Europe, books became the focus of metallic foiling. This process was often combined with embossing or beveling, which left an impression of relief on the surface.
Nowadays, this process does not use real gold leaf any more, except in very expensive editions; metallic foils are now made of aluminum or tin and are combined with a color layer to produce the desired effect. Although print houses have a standard range of foil colors, which typically include gold, silver and copper.
Hot foiling (or hot stamping), is used for the decoration of a wide range of products, is also used as an anti-counterfeiting method and is not usable with heat-sensitive substrates (polyethylene, vinyl, shrink film). Usually, delivery time for an engraved or etched stamping tool can be up to two weeks.
Hot stamping foil itself is made up of 3 layers: the waste carrier, the metallic aluminum or pigmented color and the adhesive. The stamping foil layer is produced on a thin polyester layer which is a waste product of the foil. An eco-friendly print house should dispose it properly, through local waste services.
Foiling can be done either manually, using a manual hot foil stamping machine (for low-volume jobs, invitations, limited edition book covers), or pneumatically, using an air-powered machine for higher-volume jobs. For either machine, the foiling process is roughly the same: the design to be rendered in foil is etched onto a metal plate. Then, the foil is placed between the plate and the surface of the substrate. After the plate is heated up, the foil is pasted on the printing material.
Plate prices depend on the size and the material they are made of. The cheapest dies are made from magnesium (the softer metal, which can only be used for a certain volume). More expensive dies are made out of copper, which is pretty tough, or brass, which is even stronger.
Foils come in a huge range of textures and colors, which can be split into four categories:
1- Metallics replicate the look of precious metals (gold, silver, copper). They are considered as standard by most printers, but there are more metallic foils, like rose gold or other metallic shades in red, blue and green.
2- Pigments do not offer a metallic look, but instead, come in a range of matte or gloss colors. These are great for pulling out text or logos in an eye-catching color and texture.
3- Pearls don’t look metallic, but add a pearlescent sheen to mostly transparent or translucent color, giving a more tactile shine rather than color to a design. They are a pretty, subtle choice for elegant stationery and come in a range of matte or gloss colors.
4- Holographics appear to be silver before application, but in fact they reflect a variety of colors, giving the impression of a holograph or rainbow.
Keeping parameters
Some specifications must be observed, as distances and sizes could clog under pressure. Thus, min. font size needs to be 7pt, min. line thickness 0.12 mm and min. distance between elements 0.25-0.30 mm. It is helpful to avoid hollow letters, because of their tendency to clog under the pressure of the cliché. To preserve these parameters, intervening in the client’s file sometimes is unavoidable, and the customer must be awarded.
Bleeding is possible, but sometimes, the material is too porous and draws the ink away from the intended location. This happens because the material may have an unfinished surface which absorbs liquid quickly or because the image tends to augment and become blurred. For those categories of substrate, foils with more glue are available. If material is not porous and allows the ink to remain on the surface, it takes longer for the ink to dry so it can be smeared easily.
When the stamping artwork contains large flat areas and fine, detailed linework, it is possible to lose some of those details, since a lot of pressure (or higher temperature) must be exerted in order to print. So, it is important the artwork for stamping to be balanced. Due to the high cost of tool construction, one need to try to choose the smallest possible size of repetitions and creating a plate in relation to the closest position where it is screwed onto the press machine.
The used temperature for each substrate is:
- Paper: 100 -130 °C
- Soft plastic: 80 -100 °C
- Hard plastic: 120 -130 °C
- PVC: 100 -120 °C
- Leather: 100 -130 °C
- Synthetic leather: 160 -180 °C
Stamping Tool Materials
- Magnesium Plates: Magnesium is the best material for most hot stamping, embossing and letterpress applications. Magnesium provides the most value by holding fine detail, very good transferring heat, with a reasonable cost. It comes in a wide variety of thicknesses.
- Copper Plates: Copper Plates have become largely obsolete as a result of the improvements in magnesium and other options, but still, there are some jobs in which the run length or the level of intricacy requires copper. The cost is much higher, while end up quality is unsurpassed. It is available in a variety of thicknesses, too.
- Silicone Rubber Plates: Silicone Plates are soft heat conductive dies that can be formed to fit onto a round, curved or irregular surface. They are made from a specialized rubber depending on the need of the job. They operate well in rigid, plastic, acrylic applications and a variety of flat, contoured or cylindrical shaped products. Depending on the end product, a silicone plate can benefit in production by preventing deformation around the stamped area. Silicone does a great job with gold & silver metallic foils as well as holographic and prismatic foils. Stamping with silicone dies can often be faster than stamping with other kind of plates.
- Polymer Plates: It is a very high in hardness material, but very limited, suitable for flat applications, can provide some of the advantages of silicone and it will not deform the end product like some metals may. Polymer dies are meant for one only job and have not the longevity of more.
Hot stamping foil with over-printable foil
A special category of over-printable foils is available for those cases that the customer wants a foil shade that does not exist in the ordinary palette. In other words, the stamped foil is painted with the color of the customer’s choice. The foils on which we can print with both conventional and UV inks are usually silver, matte silver, gold and matte gold.
The disadvantage of this method is that, due to the excellent coincidences required between foil and ink, the prepress operator has to “thicken” the artwork in relation to that of the foil. This consequently creates a thin color fillet around the foil, which is often obvious or misregistrated, and not aesthetically beautiful. Before suggesting this option, one must be advised by the press operator and purchasing dept.
Cold foil stamping
Cold foil takes the idea of hot foil stamping and makes it more convenient and cost-effective. The cold foil works like an additional UV ink and is a very fast lamination adhesive. It can bond in-line using a printing plate for either flexo or offset printing. It can be applied with high resolution, even for fine structures, raster gradients, halftones and thin lines; font can be legible from about 5pt and has an excellent edge definition. Smooth and not porous substrates are important for an excellent quality. The best results are obtained on glossy coated papers and papers with a smooth surface. Weights from about 80 to 500 g/m2 are possible.
The process does not require stamping tools, but uses ordinary printing plates, which are cheaper and faster to produce.
Cold foil printing can be done two ways:
a) dry lamination process (common in the offset printing industry)
b) wet lamination process, which is more versatile (dominant in flexo label industry).
The image is printed onto substrate using a standard printing plate with an ultraviolet curable cold foil adhesive. An ultraviolet dryer cures the adhesive, which becomes tacky. Foil spools from an un-wind and is nipped to a substrate. Foil sticks to the tacky adhesive. Foil that does not adhere to the adhesive remains on a thin polyester liner, while waste is directed to a rewind spooler.
Once printed, the surface of cold foil images may be varnished, laminated, or encapsulated.
Tips
- Create and add in your color library a technical ink for each type of embellishment. Technical inks are always overprinted, so while using different types be sure that elements cut, trap and overlap properly.
- Use the extended preview to check the file.
- Create one layer for each application, including die cut characterizing it as technical ink.
- Deliver a separated multipage .pdf file and also a single page file for each embellishment.
- For hot foil and embossing plate, include die cut, register holes and dowel pins to the tool supplier’s file, according your stamping machine. Some suppliers have the possibility to combine these applications, but remember that the artwork of embossing must be the same or partially the same with hot stamping, otherwise, hot foil will stick to unexpected elevated areas.
- Porous and relief substrates (e.g. wine papers) usually need gaps 4-5 mm.
- In jobs involving foiling, embossing and screen printing, the repetitions of the tools must coincide with the repetitions of the die cut. If the job requires more than one printing pass, the tools of the last one must have the same repetitions as the die cut, while the previous tool’s repetitions may differ.
- The fewer repetitions we have in the step run length, the slower the speed of the press will be.
- For digital presses, the repetitions of the step run length of the die cut should divide the repetitions of the whole step; e.g. if the repetitions of the artwork in the cutter step run length are 3, the whole print on press should have 3 or 6 or 9 or 12 and so on, and as many as possible at the maximum step length of the digital press (normally 980mm).
- Printing method, presses and material width need to be considered on costing. It may be cost significant to fill out the width of the printing machine with as many repetitions as possible. When volume is very small, choosing a narrower substrate with fewer repetitions is recommended, since plates and cutters may be expensive. Rarely, while combination of different applications stands, fewer repetitions may be important for the better result.
- Plates and cutters suit to relevant width, thickness and type of substrate and printing method.
- Lettering adjustment or magnification may be necessary for a better printing result.
The optical and tactile nature of the product increase the consumer’s experience and at the same time, the desire to acquire it makes it stand out. Although, one must keep in mind that, while the motto “less is more” is a cliché, but still, so much true; extended knowledge about technical options and equipment, combined with good understanding of nature and behavior of materials, can lead to great results.
Printing attempts extended experience and memorable items, creating beauty, strong feelings and recall memories with all 5 senses to be present, offering options, leaving free the imagination, but also keeping balance with production’s possibilities and costs.
