In the diagnostic study of pictorial artworks it is very common to use basic technicalphotographs (TP) to observe the pictorial surface and the possible alterations thataffect the works of art. When dealing with paintings on canvas, in addition to visiblephotography (VIS), racking light imaging (RL) and transmitted light photography (TL)are usually added. These techniques are used especially by the restorers, because theyallow them to evaluate the state of the pictorial layer, (cracks, cupping, tenting, paintlooses and other alterations in the support are easily recognized with that imagingproofs. In addition to TL the IRT is commonly used. It is an infrared photograph,captured around 1100nm made with the characteristic TL retro-lighting conditions.However, these are techniques to which art historians and researchers in paintingstake little advantage beyond a conservative scope, since there are very fewpublications in which, further than explaining this type of imaging there is also anexplanation on how to interpret these results, and what kind of precise conclusionsthey can offer.TL and IRT images can, in addition to provide allusive information to the state ofconservation, give some clues about the pictorial execution process. They allow theobservation of brushstrokes, their thickness, their ability to block light, while they alsopermit to observe hidden elements, pentimenti and other modifications. Furthermore,when the two types of transmitted light techniques are performed together and theresults are compared, important differences in pigment behavior can be appreciated,as they are images obtained in two or different regions of the spectrum.This article proposes an essay for the observation through both TL and IRT of thebehavior of 63 historical pigments and lacquers, (some of them produced by KREMERor SENNELIER and others handcrafted by authors by following historical recipes.) All ofthem have been bound with oil, applied on a prepared cloth with a coat of a gessoground (animal sizewith carbonate and calcium's sulfate). The area where eachpigment has been painted, is divided in four stripes: one to four layers of pigment havebeen applied there, depending on the stripe. Underdrawing lines with differentmediums have been previouslytraced perpendicularly to the stripes. TL, IR and IRT,have been carried out using a full-spectrum camera, usual for multi-band studies.The aim of the paper is to evaluate the behavior of the pigments in the two regions ofthe spectrum, comparing visiblephotographs and transmitted photography. The finalobjective is to understand aspects such as transparency and opacity, or ability to blockthe light, factors that will allow a greater systematization of this type of imaging.
Luce attraverso il colore: il comportamento di alcuni pigmenti storici nei dipinti su tela in luce trasmessa nel visibile e in infrarosso (TL e IRT)
Paola Artoni
2019-01-01
Abstract
In the diagnostic study of pictorial artworks it is very common to use basic technicalphotographs (TP) to observe the pictorial surface and the possible alterations thataffect the works of art. When dealing with paintings on canvas, in addition to visiblephotography (VIS), racking light imaging (RL) and transmitted light photography (TL)are usually added. These techniques are used especially by the restorers, because theyallow them to evaluate the state of the pictorial layer, (cracks, cupping, tenting, paintlooses and other alterations in the support are easily recognized with that imagingproofs. In addition to TL the IRT is commonly used. It is an infrared photograph,captured around 1100nm made with the characteristic TL retro-lighting conditions.However, these are techniques to which art historians and researchers in paintingstake little advantage beyond a conservative scope, since there are very fewpublications in which, further than explaining this type of imaging there is also anexplanation on how to interpret these results, and what kind of precise conclusionsthey can offer.TL and IRT images can, in addition to provide allusive information to the state ofconservation, give some clues about the pictorial execution process. They allow theobservation of brushstrokes, their thickness, their ability to block light, while they alsopermit to observe hidden elements, pentimenti and other modifications. Furthermore,when the two types of transmitted light techniques are performed together and theresults are compared, important differences in pigment behavior can be appreciated,as they are images obtained in two or different regions of the spectrum.This article proposes an essay for the observation through both TL and IRT of thebehavior of 63 historical pigments and lacquers, (some of them produced by KREMERor SENNELIER and others handcrafted by authors by following historical recipes.) All ofthem have been bound with oil, applied on a prepared cloth with a coat of a gessoground (animal sizewith carbonate and calcium's sulfate). The area where eachpigment has been painted, is divided in four stripes: one to four layers of pigment havebeen applied there, depending on the stripe. Underdrawing lines with differentmediums have been previouslytraced perpendicularly to the stripes. TL, IR and IRT,have been carried out using a full-spectrum camera, usual for multi-band studies.The aim of the paper is to evaluate the behavior of the pigments in the two regions ofthe spectrum, comparing visiblephotographs and transmitted photography. The finalobjective is to understand aspects such as transparency and opacity, or ability to blockthe light, factors that will allow a greater systematization of this type of imaging.
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