Behind the Scenes at Philaposte: Innovation Driving Stamp Printing
Reproducing with unprecedented precision, in offset and spot colors, the hues of stamps previously printed in gravure is the remarkable feat achieved by the printing division of La Poste Group.
Without necessarily knowing the details, let alone the manufacturing secrets, professionals in the printing or communication industries can easily guess that stamp printing—whether for postal or official purposes—requires highly specialized expertise.
At its plant in Boulazac, Dordogne (France), Philaposte prints 1.3 billion postage stamps annually using offset (sheet-fed and rotary), gravure, letterpress, intaglio, and even digital printing technologies. One of the latest challenges taken on by its teams was reproducing, for Japan Post, four stamps initially printed in gravure with spot colors—using the offset process.
The Process: From Source Data to Perfectly Matched Output
For this project, the input data included printed stamp samples and RGB files with a known ICC profile. The goal was to produce printed stamps colorimetrically identical to the originals. Offset printing was mandated by the project specifications.
In collaboration with software developer Alwan Color Expertise and service provider NormaPrint, Philaposte’s experts tackled this challenge. The samples to be reproduced were first analyzed to determine the target spectral colorimetric values to replicate (and not just their LAB values).
Christophe Descubes, Prepress Manager, and Thomas Demoulin, Color Specialist at Philaposte, identified three, then four Pantone Matching System (PMS) spot colors that would best reproduce the colors of the original stamps.
Alwan Color Expertise’s advanced technology took care of the rest. Using the known colorimetric values of the original RGB file, the Alwan ColorHub software separated the colors into duotone or tritone, utilizing the spectral values of the selected spot color inks previously imported into the Alwan software. No press profiling sessions were required in this specific case.

Spectral Prediction Technology
The same technology was pushed to its limits for even more precise tasks. After determining the spectral values of the four selected spot colors for the unconventional four-color printing process, a HydraChart with 160 patches was generated and printed. Measurements from this chart were then used to create an ICC profile, which could be integrated into workflows or used in Adobe Photoshop.
This approach relies on Alwan’s Hydra spectral prediction technology, which won the Pinnacle Award for Innovation in the United States in 2024. This technology allows the creation of highly accurate ICC color profiles with a minimal number of patches. “We refined the reference spot colors used through iterative processes,” explains Thomas Demoulin. After a few press trials, Philaposte succeeded in reproducing, using offset, the gravure-printed colors of the original stamps.
“We wanted to become self-sufficient with this technology that NormaPrint introduced to us,” adds Christophe Descubes. “We trained ourselves to be able to meet recurring needs for CMYK + one spot color separations. Now, we know how to do it, integrating it into our prepress processes without spending countless hours working in front of a screen.”

Learn more about our award-winning spectral profiling technology: https://alwancolor.com/software/hydrafix
Build Hydra profiles directly online:
https://colorcloud.alwancolor.com