HMC

HMC (Hidden Multi-colour Image) is an optically variable security feature produced by combining offset printing with a subsequent inkless intaglio embossing step. The process begins with a multicolour offset-printed substrate, where parallel bands of different colours are laid down across the area designated for the feature — typically a denomination numeral or short text string. A dedicated blind embossing stage then applies precise relief structures over those printed bands using an intaglio press operating without ink. The embossed elements selectively expose or shade the underlying colour bands depending on the viewing angle, creating the optical effect.

When the banknote is viewed face-on at right angles, the embossed area appears as an unremarkable single-colour field — the multicolour offset print beneath is not visible because the raised relief structure directs reflected light uniformly, obscuring the colour variation beneath. When the note is tilted away from the viewer, the image concealed within the embossed zone suddenly appears: denomination numerals or characters emerge with each element rendered in a distinct colour drawn from the underlying offset print. A further verification step is available when the tilted note is then rotated in the plane without changing the tilt angle — each character progressively changes colour as the light geometry shifts, cycling through the range of hues printed in the substrate below. The same behaviour can also be observed under UV illumination, where the fluorescent properties of the offset inks add an additional authentication layer to the feature.

The mechanism relies on the precise geometric relationship between the embossed microstructure and the position of the underlying coloured bands. Each embossed element acts as a directional reflector, and because each character occupies a zone printed in a particular colour, the colour revealed when that zone becomes visible is determined by which underlying band the viewing angle exposes. The inkless intaglio press requirement — high-pressure, precisely registered, operating on pre-printed stock — ensures that the feature is not reproducible on commercial printing equipment, and the combination of two distinct production stages (offset colour printing followed by blind intaglio embossing) means accurate counterfeiting requires both substrates. The result is simultaneously a tactile feature, a tilting latent image, and a colour-cycling animation, combining three authentication effects in a single production step.

HMC is developed and produced by Goznak, the Russian state security printing enterprise, where it is used across the Bank of Russia's circulating banknote series. The 500 rouble note in its 2010 modification is the most frequently cited reference application. The feature has also appeared on banknotes produced by Goznak for other central banks, including Syria, where HMC and the related MVC (Moiré Variable Colour) feature together form part of the authentication architecture on notes widely attributed to Goznak production. As a state-printers' technology developed internally rather than offered as a commercially licensed product, HMC is primarily encountered on currencies where Goznak is the production partner, reflecting its character as a proprietary capability rather than a broadly supplied industry feature.

Name

HMC

Category

Security Feature

Effect Types

Latent image

Company

Goznak
Company Website

Product Page

View on Supplier Site

Linked Features

3 security features