In this special guest article, UPM Raflatac explains to FoodProductionDaily.com all about shadow print, which is an inseparable part of the self-adhesive labelstock and the finished label.
The firm said the technique makes it difficult to duplicate, impossible to remove undetected and is more secure than printing on the adhesive.
They describe it as a security solution giving a warranty of origin for specified and homologated label materials.
Unlike liner printing, which is lost once labels are applied, the shadow print both originates from the labelstock’s manufacture and stays with the label for its lifecycle.
“It’s impossible to tamper with the shadow print without damaging the label face or adhesive layer," explained Fabrice Tollini, specials solutions marketing specialist at UPM Raflatac EMEA.
"There’s no simpler proof of material origin or assurance of specified label materials in such a cost-effective way – and it also gives a reliable quality of reverse-side print for branding through clear packaging."
Standard shadow print options include the UPM Raflatac logo, an identification of the labelstock or individual label components such as a luminescent adhesive, and the standard or legislation with which the label material complies.
“End-users not only have a warranty of label material origin but can very easily check that labels have the required properties to the agreed specifications,” said Tollini.
“It’s a fundamental fail-safe that the specified or homologated label materials are received and applied to the right products.”
A one-colour print, on the reverse side of the label face, is printed in light grey as the default option for text or logos.
This means the shadow print isn’t visible through non-transparent face materials, the firm said.
Based on a recurring pattern, the print is randomly distributed but regular, according to the label size and shape.
Printed on inside of glassine liner
In response to increasing requests concerning self-adhesive postage stamps, the shadow print can be printed on the inside of the glassine liner, before the silicone is coated.
It can also be rendered invisible with the help of UV-reactive inks. An invisible shadow print is especially beneficial for high value products like luxury goods, wines and spirits as well as stamps.
“UV-reactive inks provide a viable way to identify and authenticate label materials and labelled products quickly and easily, and without expensive equipment,” he said.
UV-reactive inks produce their visible colour when exposed to UV light, and revert to their colourless state when the light source is removed.
When the shadow print is printed inside the backing, it can be revealed through the backing prior to labelling; a UV shadow print on the reverse of the label face can be revealed through transparent products and packaging.
Enhanced brand perceptions
A variety of one-colour prints are possible for labelling clear packaging on items like personal care products, spirits and beverages.
“In addition to a warranty of labelstock origin and specification, it’s also realistic to say that more of the label’s surface area is now open to creative use,” said Tollini.
“The opportunity for tailoring means that label end-users and brand owners themselves are able to play a role in exploring shadow print’s informational and promotional potential. These are the people who tell us what to print.”
Reverse-side label printing has typically been performed by printing onto the adhesive.
With shadow print, a few words can be repeated along the width to allow each label to convey the desired image.