The present invention relates to the use of non-deactivatable security compositions comprising the combination of at least two types of particles of oxide materials, where said particles have a different size and/or morphology, and where the inorganic oxide materials have at least one transition metal or one lanthanide element, and radiofrequency wave absorption properties. The invention also relates to security articles, documents or elements incorporating these compositions, as well as to a method and to a system for detection thereof.

The security substrate includes an at least partially light transmitting carrier supporting a security feature and includes at least first and second layers, at least one of which covers an area which is less than a full surface area of the carrier and which at least partially overlaps the other layer. The layers have substantially the same color and texture, and the reflective contrast ratio of the overlapping areas and the non-over lapping areas is less than 20% and the transmissive contrast ratio of the overlapping areas and the non-overlapping areas is greater than 3%.

Surface modified optically variable product to provide security features in packaging materials and currency notes to prevent counterfeiting. Surface modified optically variable product is optionally readily functionalized to disperse them in organic and aqueous inks.