Foil Stamping Defined | Holograms | Planning Tips for Foil Stamping
Foil Stamping Defined
When a specific area of a digitally printed document requires an elegant, non-tarnishing metallic finish, it is easily accomplished using a process referred to as foil stamping or hot stamping. The reproduction of graphics such as logos, polished metal, or highlighted spot areas requiring a high quality reflective image can be effectively achieved by using foil films rather than metallic inks for the end result. Metallic inks, which are similar to standard printing inks, provide a rather subdued, simulated metallic appearance. The natural tendency of the ink to be absorbed into the stock contributes to a somewhat dull appearance in the desired metallic effect; however, true metallic foils are not absorbed into the substrate and therefore provide a much more realistic and pleasing metallic finish.
The foil stamping or hot stamping process (as it is called when heat is applied) is accomplished with the use of a metal plate that has been engraved with an image of the desired design required for the particular application. The plate strikes a roll of foil film, which causes the foil to adhere to the plate. The metal plate then strikes the substrate that is to be imprinted and transfers the foil onto the area of the document requiring the metallic effect. The result is a document that has a highly reflective image with a bright and dense metallic appearance.
A wide selection of foil colors, finishes, and effects are available for foil stamped documents. Standard gold and silver metallic finishes are most often used, but a wide range of other colors are used to provide a reflective metallic effect. Marble, leather, wood, snakeskin, and pearl effects are among the variety of finishes that are available and other effects, such as geometric multidimensional patterns, are used for a wide range of digitally printed documents.
Holograms: an Elaborate Form of Foil Stamping
A hologram is a 3-dimensional image that can provide a distinctive appearance to specific areas of a digitally printed application. The hologram is developed photographically with the use of laser beams as the imaging light source and special optics that reproduce an illustration or photograph as a 3-dimensional image. The image is transferred to a special foil film. A hot stamping process is used to apply the hologram to the selected substrate.
A random (wallpaper) hologram has a spectrum of color changes when viewed from several angles. The image below shows how the hologram appears in a stationary position. The hologram shown on the bottom represents how it appears to the human eye as it is moved.
Holograms designed specifically for a client's needs, such as logos or architectural images, can be expensive to produce, however, a wide variety of off-the-shelf stock graphics are available at a fraction of the cost. Diffraction foils, which are used as distinctive alternatives to custom holograms, are one of the off-the-shelf products that are available. Diffraction foils reflect multicolored images and patterns; however, they are flat in appearance. Other off-the-shelf foils are also available that provide greater depth and dimensional effects.
Holograms are produced either as registered or random (wallpaper) patterns. If the pattern or image is registered, it requires tight alignment controls for the hot stamping process. This is to ensure that the hot stamp die strikes each registered image precisely so that it is fully transferred onto the print material. Random patterns, however, are continuous throughout the foil material with no beginning or ending points. Therefore, when a random pattern is stamped into the stock, there is no need to be concerned for exact registration of the hot stamp die onto the foil pattern.
Hologram Image Types
Four types of images are available for applying a hologram to a print project (digitally printed or conventionally printed):
|1. Patterned Images|
||Patterned images are geometric designs that are uniformly repeated throughout the foil or are randomly placed.|
|2. Three Dimensional Images|
||Three dimensional images are realistic 3-D illusions of various inanimate objects.|
|3. Multiple Plane Images|
||Multiple plane images are layered and repeated several times to create a 3-dimensional effect.|
|4. Stereogram Images|
||Stereogram images are 3-dimensional images of live objects presented in active sequences. The stereogram image is the most expensive hologram to produce.|
Hologram Foil Stamping Production Process
Select an object or a model from which to work:
A model is used to create an exact image of the original in size and detail. The model is constructed from a rigid material such as wood or plastic. Wax cannot be used because of the duration of the heat of the laser focused on the model. Plastic is not the best material to use since it can expand or contract with the laser heat. The model must be built in a 1:1 scale of the desired hologram. For a 3-D embossed hologram, the depth of the model should not be greater than one inch or the hologram will become hazy. Since the hologram is designed to be used under natural or standard interior lighting, it is required that only one inch of the depth be reproduced to enable an effect of greater depth to be simulated. The model is also constructed as a distorted image in order to achieve greater depth in the hologram. A model can incorporate line art logos that are combined in order to create distinctive images.
The laser photography process:
An environmentally controlled photo lab, containing laser equipment and specially designed optics, is used to create exact replicas of the objects and models. A laser light is focused on the model or object to record the image. The laser light splits, forming an object beam and a reference beam. The beams strike the object or model from different directions and then rejoin as one beam of light. No motion can occur while the laser photo is being produced or the image will be distorted. The laser photography process results in a multidimensional image being formed at the intersection of the light waves. The image is developed on a photosensitive glass plate, which becomes the master.
The electro-forming process:
A photosensitive glass plate is placed into an electro-chemical bath where the chemicals form, or develop, the image that is recorded on the glass plate. The image on the glass plate is then transferred to a nickel die, referred to as the shim.
Transferring the image to foil:
The nickel shim becomes the embossing plate that is wrapped around the embossing cylinder on the foil embossing press. The embossing press, using both heat and pressure, brings the shim in contact with thermoplastic, which will be used for embossing the hologram image into foil, metalized paper, PVC, or polyester material that becomes the final application. For longer run applications or wider embossed images, the image, which is now a relief pattern, is copied from the shim and reproduced onto a custom embossing cylinder or drum.
Transferring the hologram image onto a substrate for further processing:
At this point in the process, the hologram is transferred onto the substrate by hot stamping or die-cutting the hologram onto the selected material. Individual die cuts are used for creating single sheet holograms or for creating kiss-cut impressions on pressure-sensitive roll stock.
Transferring the hologram onto the printed piece:
A hot-stamp press is used to transfer the image onto the materials (paper or plastic) that are used for the print project. Some images are simply transferred from the pressure sensitive label material onto the receiving material, such as security labels that are attached directly to the product package. Most images are stamped into the product directly from the foil carrier, such as holograms that are transferred to credit cards, promotional brochures, or carton faces.
Planning Tips for Foil Stamping
Foil stamping is an important addition to numerous types of digitally printed products. It adds beauty to otherwise plain documents and it provides a measure of security for a number of applications. It does, however, add a significant cost to a print project, especially if a hologram is incorporated into the design, therefore, appropriate designs and thorough planning is a must. Consider the tips described below before initiating a project that includes a foil stamp or hologram.
- Coated stocks such as clay or cast coated papers are the best types of paper for foil stamping since they are the most workable. They generally allow for a greater coverage area without distortion or breakup of the foil. However, large areas of solids can lead to complications, such as gas trapping, which can cause the foil to bubble on the surface of the stock if the die has not been sandblasted prior to use.
- Vellum surfaced stocks with 25% rag content are excellent papers for stationery products.
- Use caution if the printed piece is to have a coating applied prior to foil stamping. UV coatings or varnishes containing a high level of wax are not receptive coatings for foil stamping. Aqueous coatings or wax free varnishes provide the best surface results for foil stamping.
- If foil is being applied to laminated sheets, make sure the surface tension (also referred to as the dyne count), is higher than 40. A surface tension less than 40 will result in cracking and tearing of the sheet.
- A smooth, coated stock is the best choice for hologram images. Uncoated and textured stocks cause the image to appear dull or broken, which destroys the true effect of the hologram.
- Use caution when selecting a foil to be used on any document that will be imprinted on a laser printer because the heat of the printer can have a detrimental affect on the foil stamp. Choose a foil that has a high resistance to heat for the best results.
- Consult a Pantone Foil Color Selector when making a color selection from the hundreds of foils that are available.
- If two different foils are to be used and are to overlap, make sure the foils are compatible. Some foils will not adhere to other foil materials, so check this before proceeding.
- Set copy or create images with fonts that are greater than 8 point and lines thicker than 2 point. Use images that are open and have fewer thin lines. Foils have a tendency to fill in small, enclosed areas, thin lines, and closely kerned text. Thin serifs do not hold foil well unless the copy is stamped twice with the foil, which becomes time consuming and costly.
- It is generally best to prepare images slightly larger than the size desired. This is to compensate for the resulting dimensional change that occurs because of the paper thickness, which tends to change the size of the image.
- Copy or images with very close registration may involve extra work and greater cost. Be careful not to use trapping techniques on any artwork appearing adjacent to foil stamping.
- Screened copy and images with tone changes do not reproduce effectively into dies.
- If a bevel die is to be used, the artwork for the image and copy may need to be slightly enlarged to compensate for the image and copy reduction that occurs because of the beveled edges.
- On foil holograms, the image should be created and imprinted with rounded corners to provide the best results.
- Keep images at least one-half inch away from the edge of the stock being foil stamped in order to eliminate wrinkles that will occur if the image is too close to the edge of the stock.
- For pattern holograms, line art of the desired pattern or shape must be provided.
- For 3-dimensional images, the actual item (model) that is to become the image in a hologram must be provided. Laser technology will then be used to reproduce the image.
- For multiple-plane holograms, line art is required for all 2-dimensional planes. For 3-dimensional planes, the actual item (an actual size model) that is to become the image in a hologram is required for reproduction.
Image and Die Preparation
- If film negatives are to be made for the dies, they must be prepared emulsion side up.
- If the image has nothing to indicate the proper direction of the image, the film should be marked right read to show which side prints up. Identify the top or bottom of the image so the engraver will understand how the die must be positioned for proper foil stamping.
- Color key proofs, used for viewing the proper image direction, are of much assistance to the engraver when building a die.
- Make sure the film image is not distorted or changed in size from the original copy.
- If the application is to be embossed in addition to being foil stamped, prepare a separate piece of film or separate piece of digital artwork for each image.
- For multilevel or dimensional dies, an engraver must be provided with a solid, opaque film for each layer that will be embossed. The opaque film identifies the silhouette area of each layer. The engraver must also receive film for the line art that contains the images to be embossed. A set of color keys should be provided that are in register with the film and show the properly registered image layers.
- As a general practice, make sure the engraver has a color key, a mockup of the design, and any samples illustrating and defining the edges, shapes, and levels of the image. This will help identify exactly how the image is to appear when foil stamped and/or embossed.
General Use of Foils
- Foils can be used for logos; accents surrounding logos; borders or highlights surrounding images; and elegant accents for distinctive symbols, images, graphics, or lines.
- Foils provide security for tamper resistant seals and for documents. Holograms and foils have been used as security seals for software or video products and as a security feature on negotiable documents because they effectively display a tear if a foil seal is opened or torn.
- Because foils and holograms are difficult to reproduce, documents requiring a high level of security, such as background images on driver's licenses, membership cards, credit/debit cards, or personal identity badges, utilize foils and holograms as a security feature to prevent reproduction or counterfeiting.