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FLEXO Magazine : March 2011
Technologies & Techniques Discussing inks and substrates independently is a dif- ficult assignment. In fact, for some, it’s nearly impos- sible. The functionality of substrates and inks are interrelated and mutually dependent. After all, a package has two purposes, first to protect the contents and second to inform the user about the product. • The substrate provides protection. • The ink enables communication between the brand owner and the consumer. Success is achieved by combining these two components into a package that can adequately protect the product throughout the distribution and use cycle while providing information, advertising or decoration for the consumer’s ben- efit. Therefore, the selection of substrate and ink is critical to the package’s performance on the shelf as well as throughout the distribution cycle. In nearly all cases, the substrate is selected first, but if it is not, the printing or packaging application will dictate which substrate should be used. Often there are choices within a category of substrate, and some of these choices affect ink or graphic performance. Obviously there are many different substrates, ranging from paper and paper board to plastic films (PE, PP, PET, PLA and more). The packaging buyer will select or approve the substrate to be used, but the printer may have some latitude in choosing the substrate’s sourcing. All substrates in a category are not the same. There may be differences in physical characteristics, surface treatments or additives in the bulk material. These differences will affect the printing and converting process as well as the selection of the ink system. It is imperative to review the compatibility between sub- strate and ink for every application. In many cases, this is a simple lab evaluation to confirm the functionality of both materials. It is not unusual to discover performance differ- ences between two substrates that appear to be the same, and it is better to find them early in the process to avoid losing time and creating waste. It is crucial to ensure that when sub- strates and inks come together on press, they will meet the package buyer ’s requirements and satisfy the consumer. Selection of the ink is therefore dependent first on the sub- strate, then by the pressroom environment, regulatory compli- ance, end-use requirements and graphic requirements. Inks are often modified to make up for issues, or deficien- cies in the printing process, since an ink modification may be the most expedient “fix.” Modifying the ink is relatively quick, easy and inexpensive compared to changing equipment, or stopping the press and rescheduling the job. Although modi- fying the ink may be the most expedient corrective action, it is often done at the risk of introducing variables and unknowns into the process. Once the ink has changed, the process is different. That can create other issues, some of which may not FLEXO file photos. www.flexography.org march 2011 FLeXO 17 FLX_March11.indd 17 3/18/11 1:32 PM