Sheet-fed cold foils

As with reel-fed, DieLess™ foil stamping, API has been at the forefront of industry developments to integrate the foil application process into sheet-fed offset printing presses.

Using the same principles as narrow web coldfoil, this technique involves printing a UV-reactive adhesive and transferring the foil without the use of a die.

Compared with hot stamping, sheet-fed coldfoil is subject to the same advantages and drawbacks as DieLess™ – low set up costs, high speed and suitability for integration into the printing press but providing lower opacity and less metallic brilliance, especially on less smooth substrates.

Another limitation is the fixed positioning of the foiling unit on the press, usually ahead of the printing units. This works well for large overprinted solid areas but is incompatible with designs requiring foil text and graphics to be applied on top of a printed solid background.

As a result, sheet-fed cold foil has tended to be most widely used for greeting cards, magazine covers and promotional print as well as an alternative to laminated or metalised substrates for cartons and labels with a large area of metallic background.

In terms of foil performance, over-printability is key and compatibility with both conventional and UV-cured offset inks essential. For maximum press speeds, the foil needs to be free releasing but not so flakey that edge definition is lost or print units become contaminated with foil residues.

API’s TU grade has been proven at press speeds in excess of ten thousand sheets per hour, including long runs with minimal offsetting of foil onto print blankets. Coating chemistry gives excellent bond strength which withstands the demands of high tack UV inks.

TU is designed for use on the foiling systems of all leading machine builders, including Heidelberg, ManRoland and Foiltone/OFT.

Suitable adhesives are available from leading industry suppliers such as Saphira, Printcom and Huber for conventionally-drying, Siegwerk and Sun for UV curing or Jänecke & Schneemann, Zeller & Gmelin and Huber for both.

Due to its free-releasing characteristic, TU needs careful handling and shipping. API application support personnel are on hand to provide specialist advice and support.