Web printing process

Involves the feeding of a continuous roll (or web) of paper through the printing press. Web-fed offset lithography (as opposed to sheet-fed offset) is the predominant print process for tax stamps and other security labels.

Wet-glue application

The application of a coating of wet glue to a dry substrate before it is attached to an item. This is the main way of applying tax stamps to products.


An image in paper produced by varying the thickness and density of the paper mass during paper production. These variations form a discernible image that can be viewed when holding the paper item up to the light.


A property of electromagnetic radiation that denotes the distance between waves of light.

Wavelet transform

A mathematical means for performing a signal analysis when signal frequency varies over time.