METAMERIC INK PAIR

Special security inks (usually a pair of inks) which look similar in one type of illumination (e.g. in visible light) but show a noticeable difference in another type of illumination (when using a light filter).

a —  Paper substrate; 

b —  Parts of the image are printed in different inks (metameric ink pair). In visible light there is no difference in the colour of image parts; 

c —  Image parts differ in colour. Viewed through a red optical filter

a —  Paper substrate; b —  Parts of the image are printed in metameric inks. Offset printing; 

c —  A dark profile of a bird is clearly visible. Viewed through a red optical filter

a — Hybrid substrate. The text DO NOT STAMP THIS PAGE is printed in metameric inks; 

b — In the text DO NOT STAMP THIS PAGE the words do not differ in colour. White light; 

c — The words STAMP and THIS differ in colour. Viewed through a red optical filter