Penetrating inks for printing
Penetrating inks are black inks, containing pigments which are able to deeply penetrate and migrate through the fibres of a paper substrate.
The ink remains black on the front side of the document, while on the reverse side it migrates as red or pink.
Penetrating inks are commonly used in MICR printing and printing with the use of numerators. The prints secure the authenticity of documents.
A forger cannot remove or successfully copy the number because it is visible on the reverse side of the substrate. The intensity of migration depends on porosity of the substrate.
The best effects are obtained by using offset paper with the grammage lower than 110 g/m².