The new lighting system had to provide carefully controlled illumination of ancient walls, tombs, mosaics and bas-reliefs while remaining visually unobtrusive.

The coating also needed to withstand persistent high humidity and provide long-term corrosion protection for the lighting equipment.

Controlling Light Reflection

The lighting concept was developed by Zumtobel in collaboration with Italian lighting designer Prof. Arch. Alessandra Reggiani.

The design guides visitors from the brightly illuminated interior of St. Peter's Basilica into the darker archaeological environment beneath the church.

One technical challenge involved minimizing unwanted reflections from the luminaires, particularly their anti-glare grilles.

Through testing and adjustments to the coating's pigmentation, Interpon and Orion developed a black powder coating designed to absorb most diffusely reflected light.

The finish helps the fixtures blend into the background while directing visitors' attention toward the illuminated historical features.

"What began as a search for a coating, absorbing most of the diffusely reflected light, evolved into a journey of experimentation, innovation and collaboration," said Dr. Kai Krauss, senior technical market manager at Orion S.A. "Through extensive trials and combining the powder coatings expertise at AkzoNobel and the carbon black expertise at Orion, the team finally developed a black powder coating that offered the ideal solution."

Corrosion Protection Under Extreme Humidity

The Vatican Necropolis presents demanding environmental conditions for exposed metal components.

Relative humidity levels range from approximately 98% to 100%, while temperatures remain around 20 to 25 °C.

AkzoNobel's Interpon Redox One Coat was selected to provide corrosion protection and the specially developed black finish in a single coating layer.

The system was designed to meet the project's appearance and durability requirements without compromising the lighting concept.

"For a project of this significance, our focus was on delivering a coating solution precisely tailored to the customer's technical and aesthetic requirements," said Jeff Jirak, managing director of AkzoNobel's Powder Coatings business and member of the company's Executive Committee.

"Our primary contribution was to ensure reliable, long-term corrosion protection under the extreme humidity conditions of the Necropolis without compromising the integrity of the lighting design. The close coordination with Zumtobel and Orion ensured that each area of expertise contributed seamlessly to the overall result."

Matteo Cundari, managing director of Zumtobel Italy, said the historic site required an individualized lighting solution.

"Projects of this type most often require a very specific approach and an individual solution that is as unique as the locations themselves. We're very proud to have contributed to giving new light to the Vatican Necropolis."

The restoration demonstrates how pigmentation, appearance control and protective performance can be integrated into a specialized powder coating for a demanding installation.

The project illustrates how formulators can balance optical properties, pigment selection and corrosion resistance for specialized applications. Explore PCI's coverage of powder coatings.