Induction sealing to glass substrates is historically considered one of the most difficult engineering challenges in the packaging industry. Glass containers are highly rigid, and their manufacturing process—molding molten silica at extreme temperatures—often results in minor topographic variations across the sealing surface, such as "saddles," slight dips, or microscopic wave patterns. Furthermore, glass possesses an extraordinarily high surface energy and is entirely inorganic, requiring highly specialized polymer adhesives capable of forming strong intermolecular bonds with silica under the rapid, violent thermal cycling of induction heating.