Running hot and cold

Running hot and cold

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Whilst advancements in cold foiling techniques have made both web-fed and sheet-fed decorative cold foils an accessible and affordable option for packaging designers and printers, hot stamping foils offer the true brilliance required by high-end luxury brands. 
 
Here, Will Oldham Managing Director at API Foils, discusses the differences the techniques, as well as the importance of defining application, substrate, budget and finish requirement when selecting the appropriate process.  
 
Web and Sheet-fed Cold Foiling
 
Promoted as the accessible and affordable option, when correctly applied, cold foiling can provide impressive results. Although the mirror-like finish achieved through hot stamping is not fully replicable, there are numerous instances where the aesthetics, costs and flexibility of cold foiling is preferred.  
 
One application where cold foil is particularly suited is on heat sensitive substrates, like filmic labels and shrink sleeves. It works well on the ‘no-label look’ labels, which are growing in popularity for products such as shampoos and beers. Being a cold process, it is the UV curing that sets the foil rather than a hot stamp die, which eliminates heat damage on sensitive substrates. 
 
 
A major advantage of cold foiling is price. The cost-effectiveness of the technique is down to two key characteristics, the flexographic printing plate and the inline production capabilities.
 
A flexographic printing plate is approximately 98 per cent cheaper than the traditional hot foil stamping dies. The low manufacturing cost and the flexibility to produce the plate in-house enables printers and designers to react to seasonal, buying or promotional trends quickly and relatively cheaply, whilst incorporating a metallic finish into their designs. 
 
Unlike hot foiling, where the process has to be offset from the rest of production, cold foiling is able to run at full rotary production speeds. This means that fast moving goods are able to achieve that foil effect – something not always possible because of time and cost restraints of lower value commodity products.
 
Hot Foiling
 
Despite cold foil’s affordability, it is not always the cheapest option. It is imperative that each application, substrate and design is analysed by a technical expert to ensure optimum quality is achieved at minimum cost. For example, because some cold-foiling processes require the foil to run the entire length of the substrate, applying small details will waste a considerable amount of foil, and money. In those particular cases it would actually be cheaper to use hot foils or web-fed cold foils. 
 
Hot and cold foils both look best on flat, smooth surfaces, whereas fibrous, textured, dry and absorbent surfaces tend to break up the structure of foils and instead of reflecting light they can diffuse it. The benefit of using hot foil over cold foil is that pressure is applied when using the hot stamping die, flattening challenging substrates. The laydown of cold foils and lack of pressure in the application process makes it unsuitable for these types of substrates. 
 
Despite the progress made in the quality of cold foiling, the industry cannot and does not deny the superior quality and true mirror shine of hot foil. This is due to the thickness of the metalised layer. Cold foil requires a thinner layer due to the need to allow UV energy to pass through the layers of the foil, so it can activate the UV curable adhesive. The thinner layer allows the transmission of light through the other layers, activating the cold foiling process. If a normal thickness of metal were applied it would render the cold foiling process useless. The metalised layer in hot foil is thicker, and therefore creates a superior shine, essential when a true brilliance is required by high-end luxury brands.
 
It is of paramount importance that cold foiling is not seen simply as a cheaper alternative to hot foil. Hot foil is the only way to create a true mirror-shine and the luxurious effect required for top-end packaging. What cold foil does offer is a viable solution for products that ordinarily would not be able to achieve a decorative foil effect, due to cost and time implications. 
 
Regardless of whether hot or cold foil is specified, it is important to remember that to get the best out of decorative foils the compatibility of the adhesive, substrate and foil all need to be considered, viewing it as a complete solution rather than an individual product selection.
Stephanie Cornwall
Stephanie Cornwall
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