Buon fresco- The "true" (and most demanding) fresco in which pigment is applied to a damp plaster surface. As the plaster dries, a chemical reaction produces a calcium carbonate surface. The crstalline structure of the wall reflects light and the fresco appears to glow from within. These crystals also lock the molecules of pigment in place, forming a nearly indestructible, hard-as-a-rock surface. (The oldest known artworks, the cave paintings in Lascaux done 17,000 year ago, are paintings done on limestone surfaces.). The aging of a fresco also demands that the artist predicts a color change. As the lime reacts with the pigment, colors appear lighter. Color for shading is usually mixed in a dark, medium and light. The medium tone usually is applied as a base coat and the lights and darks worked onto that.

Canson- A tough French paper that comes in 5' by 30' rolls used for drawing the cartoons.

Cartoon- Full scale blow up of smaller sketches.

Chiaroscuro- An Italian term meaning light and dark.

Conte- A small compressed chalk crayon, approximately 3" long, made in France. The best red chalk (now scarce) comes from the Island of Elba just off the Italian coast.

Day marks- The visible lines that are left between giornate. (They arre easily seen in Michelangleo's "Creation of Adam"). Day marks are carefully retouched to blend them into the fresco.

Fresco- (from Italian "affresco," meaning fresh). Pigment applied to a plaster surface. Fresco technique was thousands of years olf before oils were in common usage.

Fresco secco- Pigment is applied onto dry plaster usually with egg (tempera) as a binder.

Giornata- In Italian, "the work that can be done in a day ." A fresco, which resembles a giant puzzle, is painted in sections as necessitated by the drying plaster. The size of the giornata depends on what is to be painted in that section

Giornate- The plural of girnata.

Grid lines- Are superimposed on drawings, cartoons, tracings, and the wall to facilitate placement of the compsition.

Grinding white- Chuncks of sun-dried slacked lime are damped with distilled water and ground to a creamy consistency. The resulting putty is caustic and will burn the skin. It is then used alone as the color white or mixed with other pigments. Only a tiny amount of lime can be ground at a time.

IntonacoThe final layer of plaster composed of 1 part very fine sane to part lime. The actual painting is done on the still wet intonaco. The intonaco is applied early in the day. The surface is very slick like the surface of a polished stone. The artist must wait 1/2 to 2 hours for the plaster to set enough to be ready for painting. The moisture from the plaster and the paint moves into the substrate as it dries. The surface can accept paint, or pull pigment, for 8-10 hours. When the wall reaches complete saturation, painting must cease.

Ora d' orato- During a certain period in the saturation process, the most rapid transfer of paint can take place. This period may last several hours and is the time when paint can be applied very fast. In Italian, this prime period (oro d' orato or "the golden hour"), is when the plaster pulls the paint just right.

Pouncing- A large needle is used to punch holes abot 1" apart into a tracing. The tracing is held in position against the wall. Tapping a gauze bag filled with pigment, either red (sinopia) or grey/green (terra verde), over the needle holes produces a dotted outline of the cartoon on the wall. The sploveri are then connected to produce faint line drawings that are used for positioning the composition. The actual painting is done by referring to the various preparatory images.

Preliminary drawings- A fresco design is a process of continued refinement. Many studies of poses are done until the composition is complete. Drawings (as many as 50 to 60 sketches per section) are done 1/2 life size and transferred to the scale of the actual fresco. Drawing are done in various media, including studies for color composition. Detailed portions may be studied as oil paintings.

Scartch coat- The first layer of plaster or base coat, combed to leave a gooved surface that prvides better adhesion for the second coat.

Sinopia- The red/bown pigment name for Sinope, the city in Asia Minor for which it comes. Also used to refer to the red under-drawing resulting for connecting the splveri.

Slaking- A process that take place in a "pit" during which heated carbonate of liem (in the form of chalk, limestone or marble) has water added to it, producing calcium hydrate. The reaction is exothermic, reaching 200+ degrees Fahrenheit within seconds, and potentially explosive. Properly protected and aged, well mixed slaked lime yields a butter-smoot plaster putty. Poorly slaked lime yields plaster that will crack. The slaked lime for "The Prodigal" fresco was purchased in powdered form.

Spolveri- The series of dots left on the wall after pouncing.

Substrate- The "base" of the fresco. The structural support behind the plaster. The substrate for "The Prodigal" fresco is a specially constructed brick wall that allows for proper ventilation of the work.

Tracing- A Translucent plastic sheet placed over a cartoon which is then traced with a pencil. These are use (and reused) to map the composition onto the wall.