D-Met is a process that removes metal from a metallized substrate in a specific pattern, leaving a window (or several windows) in an otherwise metallized film. The process tolerance is very fine, and you can have anything from a simple window, to extremely intricate and detailed patterns of clear and metallized areas. It’s a great way to make an impact on the shelf, but it’s also a way to gain some additional barrier.
Conventional wisdom says that a hole in the metal will ruin the barrier—air will penetrate the package at the weakest point and ruin the product. This is true for D-Met as well, with one caveat; it only applies to modified atmosphere packaging, such as nitrogen-flushed packages. For everything else, there’s a linear relationship between barrier and metal coverage. In other words, if you have metal covering 90 percent of the package and 10 percent is a clear window, then the barrier is 90 percent of the barrier properties of a fully metallized package.
The reason for this relationship is actually pretty simple. There is no pressure on the air inside the package to reach equilibrium with the air outside the package, since they are the same gas. Therefore, the air inside the package stays mostly inside, and the air outside the package stays mostly outside.
To date, there are very few companies taking advantage of this little known fact. You may have seen a line of bags from a large, nationwide chocolate company use demetallization, as well as a few brands of tortilla chips that use a stripe-metallized bag. Both are great examples of adding barrier (and optics!) without a lot of cost. Sure, D-Met does involve two additional production steps compared to a clear web, and that does add cost. But compared to other clear high-barrier films, like AlOx or SiOx, where the base web alone can cost well over $7/lbs, D-Met is a very affordable way to increase shelf life and the appearance of metal-backed inks.