Art Terms Glossary beginning with D

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Daguerreotype: The first practical photographic process. A copper plate coated with highly polished silver was sensitized to light with iodine fumes to form silver iodide, which darkens very slowly upon exposure to light. After exposure in the camera, the latent image on the plate was brought out (developed) in mercury vapor, made permanent (fixed) with hyposulfite of soda, and rinsed. The result was a positive picture, which could not be multiplied and had to be protected by a glass cover because its surface was fragile. Announced by and named after the Frenchman Louis-Jacques-Mandé Daguerre (1787-1851) in 1839, the daguerreotype has remarkably clarity. Because of the mirror-like surface of the plate, however, the picture must be viewed at a certain angle. Daguerreotypes were produced in six sizes, ranging from whole plate (6½ x 8½ in./16.5 x 21.5 cm) through half plate (4½ x 5½ in./12 x 16 cm) to sixteenth plate (1 x 1 in./3.5 x 4.2 cm).
Daily Office: A complex round of prayers and readings formulated for recitation at the canonical or liturgical hours of the day and required of all clergy, monks, and nuns: matins (about 2:30 am), lauds (5:00 am), prime (6:00 am), terce (9:00 am), sext (noon), none (3:00 pm), vespers (sunset), and compline (9:00 pm).
Dendrochronology: An examination technique that uses the number and width of annual growth rings to date wood. The sequential variations in a tree's ring width correlate to the annual climatic conditions for its local geography. Measurement of 50-100 years of growth rings visible on an artwork is compared to master charts for a specific geographic zone to determine the active growing years for the tree before it was felled.
Destructive Optical Microscopy: An examination technique which uses complex optical microscopes to examine samples taken from an artwork at high magnifications using plane and cross polarizing light to identify components by cataloguing optical properties. Additional chemical tests are sometimes performed under the microscope to aid in identifications. Sample preparation can vary depending on the material, ranging from particle mounts taken from specific areas to cross-sections that show the structure or stratigraphy of a larger area. For instance, the layering sequence of paint and varnish can reveal much about the technique and history of a painting. Sometimes sections are embedded in plastic resin and polished to maximize the information gathered.
Developing-out paper: Papers coated with a chemical emulsion, exposed to light, and immersed in a chemical bath until the image appears, or is developed out. These light-sensitive papers are used in the chemical development of enlarging or contact-printing. The predecessor to d.o.p. is albumen printing-out paper (p.o.p.).
Donor: An individual who commissions an artwork for presentation to a church or other institution.
Drollery: Animal and human hybrids that inhabit the initials and foliate borders of Gothic manuscript leaves.
Dry collodion negative: A variety of negatives on glass with a hygroscopic agent in the coating that will allow sufficient retention of moisture to maintain the light sensitivity for a short period of time. One of the earliest dry collodion negatives introduced by George Shadbolt and Farnham Maxwell Lyte in 1854 used a honey process, which was further modified by John Dillwyn Llewelyn two years later with acidified honey (oxymel). Other processes followed using tannin, gum, sugar, tea, coffee, and various collodion combinations with albumen, gelatin, and silver bromide. Although each variation had its supporters, and the dry collodion negatives freed the photographer from the requirement of a nearby darkroom, these processes all lacked the superior sensitivity of the wet collodion negative. It was only after the introduction of the gelatin dry plate negative that the wet collodion negative faded into obscurity.
Drypoint: Drawing directly on the copper plate with a sharp point creates a rough ridge of metal - a burr - along the furrow. When the plate is inked, the burr catches the ink, producing dark, velvety accents.
Duratrans: A type of transparency made by Kodak, commonly used for display purposes in advertising and trade shows.
Dye diffusion transfer process color print: A print whose emulsion material is composed of multiple layers, including a final backing layer, that together create both the positive and the negative. The three principal layers are sensitized to the primary colors of light (red, green, and blue), with corresponding dyes and developing agents sandwiched in between. Exposure of the print starts the chemical development process, in which the dyes diffuse through the layers of chemicals forming the positive image on the print backing. The colors of the resulting print are unstable and susceptible to fading. The Polaroid process, developed by Edwin Land (1909-1991) and marketed since 1948, is an example of this technology. Polaroid polacolor is an instantaneous photographic print, first developed in 1965. The prints have a built-in development chemistry that requires no additional laboratory processing. Exposure and processing the film both take place within the self-contained, sealed film packet. Individually sensitized residual layers of blue, green, and red dyes are sandwiched in between layers of developing agent. When the film is exposed, the developing process begins. Each light sensitive layer records the components of the subject colors, and the dye developer diffuses out the negative into a receiving layer to create the positive image. Significant color loss and shift are characteristic of this short-lived process.
Dye transfer process color print: Also referred to as dye inhibition or wash-off relief process. The process was originally introduced by the Jos Pé Company in 1925. The subject is photographed through filters that are dyed cyan, magenta, and yellow. The filters are then contact-printed in register on a single sheet of light-sensitized, gelatin-coated paper to form a full-color image. The pigments of these primary colors are less susceptible to fading and considered relatively permanent.