Choosing the proper coating is an essential step in designing and producing quality packaging. Why are coatings important? For some of the same reasons that packaging is important. While packaging protects and enhances the beauty of what’s inside, coatings help protect and enhance the appearance of the package itself. Because coatings are dually decorative and protective, they are an economical way to extend both the appearance and the lifespan of the package.
One of the goals of packaging is to catch the consumer’s eye, encouraging them to examine and explore the package and its contents. A quality coating further increases shelf appeal by imparting additional tactile elements and adding snap to printed graphics. The most common types of coatings used today are UV and aqueous. Both are available in a range of finishes from matte through satin to gloss, expanding design flexibility beyond the choice of inks.
A coating also protects the package from the rigors of assembly, fulfillment, shipping and distribution, safeguarding it from fingerprints, abrasion and scuffing. UV and aqueous coatings both demonstrate excellent abrasion and block resistance; in some cases, effectively eliminating the need for shrinkwrap or other protective layers.
Which is the best coating for a job? That depends as much on the job as it does on the coating. Expectations of performance, appearance, quality and cost are variables to weigh when making a decision. Other factors to consider include operator experience, job latitude (tolerance), storage conditions and performance requirements. We’ll begin with a comparison of UV and aqueous coatings, and then discuss the most appropriate applications of each.
Aqueous coatings are approximately 60% water and 40% solids. During the drying process, the liquids evaporate or are absorbed by the substrate, leaving the solids to form a thin film. Aqueous coatings are clear and odorless when dried, and are also available in FDA-approved formulations for use in food packaging.
UV coatings are 100% solids, and finish by light-curing rather than heat-drying. The solids cross link to form a durable plastic film that provides unparalleled gloss and hardness. UV offers a broader range of finishes than aqueous, including options such as metallized flakes or pearlized pigments. Although UV coating can be applied either in-line or off-line, in-line UV coating offers comparable finish quality plus the advantages of increased speed and reduced cost compared to the off-line UV coating process.
Both UV and aqueous coatings offer the convenience of in-line application and rapid drying, allowing for instant work and turn. In fact, either type of coating can be used with little or no spray powder, improving smoothness and creating a cleaner work environment. In addition, both coatings can be applied as an overall or “flood coating”, or as a spot covering to highlight a particular image or area.
Aqueous coatings generally cost less up front, but the quality advantages and productivity gains of a UV coating usually outweigh the higher unit costs. When comparing costs it’s helpful to think of UV as conferring all of the benefits of aqueous coating,
but to a greater degree. For example:
Aqueous dries fast — UV dries fasterAqueous can be glossy — UV is glossier Aqueous provides protection — UV provides more protectionUV coatings are particularly well suited for:
Applications requiring the ultimate in gloss Applications requiring the ultimate in hardness Non-absorbent print surfaces (e.g. plastic, Tyvek ®, etc.) POS displaysSpot coatingAppropriate applications for aqueous coatings include:
Food packaging (for direct food contact) In-line heat seal blister packaging Primer / seal coating (to enhance gluing or subsequent UV varnish over conventional inks)Items that will be written on (e.g. mailers, postcards, etc.)When you choose a coating you make an investment in the lifespan and performance of the package, and ultimately of the product inside. The more closely the package will interact with consumers or end users, the stronger the case for incorporating the coating into the overall design.
Copyright ©2005 by Dennis Bacchetta. All rights reserved.
About the Author
Dennis Bacchetta is the Marketing Manager at Diamond Packaging, a leading folding carton manufacturer and contract packaging supplier. He frequently writes on industry topics and technical issues. You may contact him at dbacchetta@diamondpkg.com.