Infrared Fluorescence Photography (IRF)

Infrared Fluorescence Photography (IRF)

Infrared Fluorescence photography is a useful method for the examination of works of art and archaeology. It is part of the Technical Photography documentation and allows to detect Egyptian blue and cadmium-based pigments.

Infrared Fluorescence phenomenon 

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Some molecules and minerals (among them mineral pigments) exhibit Infrared Fluorescence. This phenomenon is similar to Ultraviolet Fluorescence where a beam of ultraviolet light produces visible light emission. In the case of infrared fluorescence, a beam of visible light generates an emission of infrared radiation.

Infrared Fluorescence is observed in a few rare minerals but also in a very common molecule, chlorophyll. Chlorophyll emits infrared fluorescence in the very near infrared. Indeed, its fluorescence is brighter in the IRF 850 image – where the 850 nm filter was used, allowing through the closest infrared. Notice that, on the other hand, the infrared fluorescence emission of the cadmium red swatch is almost unchanged since it happens at a longer wavelength (over  850 nm ).
This photographic method can be made using ALICE (VIS-only) lamp or FABRIZIO UV lamp. We call the methods, respectively, IRF-VIS and IRF-UV, indicating that we are using the ALICE lamp or the FABRIZIO lamp.  The UV lamp is recommended to increase the emission from cadmium pigments while the ALICE lamp is fine for Egyptian blue.

Applications for Art examination

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Among historical pigments, Egyptian blue, cadmium red, and cadmium yellow are the ones exhibiting infrared fluorescence. As the name says Egyptian blue is the blue actually used by the Egyptians and Romans. So, infrared fluorescence photography is used in archaeology to detect even tiny fragments of Egyptian blue pigment.

Experimental Set up

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We need a source of Visible only-light (ALICE lamp) and the camera set up for IR photography.

Applications

Infrared Fluorescence Photography for mapping different inks.

We can distinguish and map different inks, see this experiment!

ADVANCED IRF with ANTONELLO Multispectral Imaging System 

Identify more pigments with ADVANCED Infrared Fluorescence Photography
Discover the power of ADVANCED Infrared Fluorescence Photography with ANTONELLO, The Multispectral Imaging System. Our 6 Infrared filters allow you to identify more pigments and unlock the secrets of your artifacts. Get yours today and start exploring!

References

Publications on Infrared Fluorescence photography (IRF)
A. Cosentino "Infrared Technical Photography for Art Examination” e-Preservation Science, 13, 1-6, 2016.
A. Cosentino “Iden­ti­fi­ca­tion of pig­ments by mul­ti­spec­tral imag­ing a flow­chart method” Her­itage Sci­ence, 2:8, 2014.
A. Cosentino, S. Stout "Pho­to­shop and Mul­ti­spec­tral Imag­ing for Art Doc­u­men­ta­tion” e-Preservation Sci­ence, 11, 91–98, 2014.
A. Cosentino "Effects of Different Binders on Technical Photography and Infrared Reflectography of 54 Historical Pigments” International Journal of Conservation Science, 6 (3), 287-298, 2015.