Glossary Traditional Terms


The arrangement of pictorial elements in a work of art. Matisse made many changes to his compositions as he worked, adjusting the size and shape of different areas in relation to one another and, in the case of paintings and works on paper, to the edges of the support.

State (état)

A compositional shift made in the course of producing a work of art. Matisse sometimes documented a state of a painting or a sculpture, often engaging photographer Eugène Druet. After 1914 the artist also used prints to document states of paintings.


Derived from the Italian word for repentance, this traditional term describes the unplanned reappearance of a previous or changed compositional element in a paint layer due to the increasing transparency of the oil paint layers over time. There are few traditional pentimenti in Matisse’s works from 1913 to 1917, as he purposefully incorporated his reworking into the final work of art.

Bas relief

A sculpture in which the forms are built from a flat background plane, different than a freestanding sculpture. Matisse made only eight bas-relief sculptures, including the four Backs. For his first state of Back, Matisse likely worked on a table, rolling out the soft clay into large sheets that he then firmly pressed onto a nail-studded board. The thickness of the clay must have been sufficient for him to manipulate it with his fingers, producing the rolling topography of the background. The artist could easily have added clay to the figure to create the higher areas of the relief.

Examination Techniques

Artworks can be studied by examining the thread count of a canvas; the chain patterns of paper; and the front, back, and edges of paintings and works on paper. These as well as sculpture can be examined under magnification and with raking and specular light, ultraviolet radiation, infrared reflectography, and X-radiography. In addition, various methods of scientific analysis and imaging techniques were developed specifically for this project.

Cross sections

A small sample of a painting that includes the surface, paint, and ground layers, usually from an area of loss or along the edge of the canvas, which is mounted in a silicone mold, sandwiched between two layers of hardened transparent resin, and ground and polished to expose all the layers of paint in one plane. Prepared cross sections can be examined and documented with a reflected light/fluorescence microscope equipped with a digital camera; this technique was employed to analyze the cross sections from Bathers by a River.

Raking, specular, and transmitted light

Various lighting arrangements can highlight features on works that are not easily captured with normal illumination. To examine a painting in raking light, lamps are positioned at a low angle to a canvas, so the light travels from one edge of the object toward another, exaggerating the surface texture and deformities by enhancing their shadows. To study a drawing, for instance, in specular light, lamps are positioned perpendicular to the surface of the sheet so the light is reflected directly back to the viewer, highlighting variations in surface sheen and planar deformities. Light transmitted through the front of a canvas accentuates thinly and thickly painted passages, identifying unpainted areas in greater detail.

Ultraviolet illumination

Ultraviolet radiation is used to help characterize surface coatings, pigment composition, and reworkings or restorations. Artist’s materials, including some pigments, exhibit specific fluorescence colors in response to ultraviolet radiation that aid in their identification.


Dr. Sotirios A. Tsaftaris and Dr. Aggelos K. Katsaggelos of Northwestern University developed a complex software protocol to recolorize a historic photograph of Bathers by a River in order to better understand Matisse’s palette and working methods. They correlated black-and-white photographs with the color of the finished painting and spread the color information to as many pixels as possible using algorithms and equations based both on the grayscale intensities of the photograph and on the likely extent of hidden color areas (visible to researchers in cross sections, paint losses, and earlier areas of the painting that Matisse left exposed in his reworking).

Laser scanning

The process of shining a laser line over the surface of an object in order to collect three-dimensional data. This data is captured by a detector, or camera, that is mounted in the laser scanner and records the line as it shines on the object. With knowledge of the location of both the origin of the laser and the detector, software triangulates the image of the laser line into accurate, dense, three-dimensional coordinates, or points. As the laser line passes over an object, tens of thousands of such points can be collected in seconds; these are later processed into a digital model that shows surface details and can be used for accurate comparisons of surface contours. The laser scanning for this project was performed by Direct Dimensions, Inc.

Infrared reflectography

Infrared imaging exploits the varied transmission and reflection properties of artists’ materials and is used to distinguish pigments, inscriptions, underdrawings (particularly those done in carbon-rich materials such as charcoal and pencil over a white ground), and changes in a composition not visible to the naked eye.


X-radiographs are obtained by exposing a painting to X-radiation and then capturing the image on film or digitally. Digital images can be manipulated with software designed to assemble individual X-ray films into a composite picture of the entire canvas and support. X-radiography can reveal changes in the composition, the density of paint layers, and details in the support not visible to the naked eye.

Scientific Methods of Analysis

A variety of scientific techniques can be used to identify materials from a work of art. Individual pigments can be identified with polarized light microscopy or scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. Paint samples that are mounted as a cross section reveal their layer structure when viewed with a reflected light/fluorescence microscope and can also be analyzed with SEM/EDS. In addition to pigments, the medium or binder from a paint layer can be identified by means of Fourier transform infrared microspectroscopy and gas chromatography-mass spectroscopy.


Digitized images of a painting—such as X-radiographs, infrared reflectograms, and photographs of earlier states—that are aligned over one another to determine how Matisse changed particular features of a work over time.

Digital imaging techniques

For this project, Dr. Robert Erdmann of the University of Arizona developed sophisticated software to unite multiple archival images that were taken from an oblique angle or otherwise distorted, aligning them into the same plane. He used the same software to automatically unite individual films into composite X-radiographs and infrared reflectograms without distortions or tonal discrepancies.