Circulation Simulator Method for Evaluating Bank Note and Optical Feature Durability

摘要

Effective long-term authentication of optical security features on bank notes requires a sound substrate that can withstand the rigors of circulation. Crane & Co. has developed a test method that simulates the deterioration observed in actual circulated bank notes: soiling, creasing, tearing, edge tatteredness and limpness. The method relies on the physical degradation of note specimens that are weighted on each corner and tumbled in a medium of glass beads, metal discs and synthetic soil. Durability is judged by how well a note retains its initial optical and physical properties after being subjected to the conditions of the Circulation Simulator. Much of our early research was directed at improving the paper substrate, and evaluating surface treatments that resist soiling since excessive soiling is often the primary reason bank notes are removed from circulation. Recent work has examined the correlation between Circulation Simulator results and the properties of actual bank notes culled from circulation. We also are using the Circulation Simulator method to qualitatively evaluate the potential durability and effectiveness of optical security features such as electrotypes, watermarks, windowed threads, foils and inks. This paper provides a description of the testing and analysis methods.