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and handling of the lime. Though care must be taken to guard againstfreezing temperatures, tanks also may be located above ground.

By the time the pit is filled and capped, many gallons of distilledwater and quantities of the purest available lime will have been

combined, small batches at a time, and poured into the pit to beginthe breakdown of the mixture into a soft, gritty paste. The chemicalbreakdown of the lime crystals, called slaking, must continue until itis smooth enough to be used as plaster for the skin, or finishedpainting surface.

The Scratch CoatIn the meantime, many buckets of the partially-slaked lime will be

combined with sand (two parts rough washed sand, one part lime) tocreate the scratch coat, a three-quarter-inch or more layer offoundation plaster troweled onto an existing interior wall. It is to thisroughly-scored scratch coat that the final eighth-inch-thick skin isbound. The scratch coat, applied in two or three layers severalmonths apart, may be reinforced by a membrane of metal meshbetween the plaster and the wall. A typical Renaissance-era wallconsisted of brick, which allowed the finished fresco to bind and drywith relative ease. Brick is not the common interior constructionmaterial it once was, so products like Densglass mounted on areinforced masonry wall may serve today as a wallboard backingsuitable for the scratch coat. Large-scale frescoes weighingthousands of pounds requires close consultation with the architect of

the building.

SlakingThe process of mixing water with powdered lime is fraught with

hazards. The combination produces a volatile chemical reaction,which creates enormous amounts of heat and steam. A fifty-poundbag of lime should be laid flat on the rim of a heat-resistant 55-gallonbarrel containing 11-14 gallons of distilled water. Slitting the bagalong its length, the mixer then dumps the bags contents into thewater all at once and loosely covers the barrel with the empty bag toprevent splattering. Within a very short time, the mixture will begin

roiling, bubbling and steaming, shaking the barrel with its vigorousaction. Workers should wear protective clothing and a Plexiglas faceshield to avoid the 400-degree spatters of wet lime and large volumesof steam escaping the mixing barrel. Despite these discomforts, themixer must remain at the barrel using an industrial drill and extendedpaddle bit to ensure the batch is completely blended into a looseslush before it is poured into the pit. Once filled, the pit is then sealedin such a way as to minimize exposure to pollution and othercontaminants. The pit should be checked regularly against waterleaks and freezing. Additional distilled water can be periodically

stirred into the mixture to maintain moisture content.

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CompositionFresco painting technique, because of the repeated cross-hatching of

earth pigments onto the absorbent skin, resembles drawing as muchas, or more than, painting. Long before approaching the wall, theartist begins with pencil, charcoal or cont drawings of models or

other physical elements that will make up the overall preliminarycompositional drawing. The compositional drawing is typically madeon a one-inch to one-foot scale, though it has been suggested thatusing metric measurement greatly facilitates transference of griddeddrawings to full scale. These initial drawings -- both individual sketchstudies and the compositional drawing containing these elements --require an artist with a keen instinctual eye for exactitude. Precisionis critical when it comes time to enlarge the compositional drawing tofull-scale size.

StudiesOnce initial drawings are completed, the artist may create more fully

refined drawings of certain elements such as portraits to fix themeven more firmly in the mind. In theory, this fixing-in-the-mind,while appearing somewhat repetitive, is an important processthroughout the course of conceptualization. It allows the artist to notonly embed the subjects into memory, but to also discover new andserendipitous aspects of the original inspiration for the composition.

An oil color study of the full composition, generally the same size asthe compositional drawing, should also be prepared. Color rather

than detail, as in the drawing is emphasized. The artists knowledgeof color, through experience in easel oil painting, comes heavily tobear. Here the artist more fully visualizes how color may affectcomposition, taking into account the weight of certain colors inbalance with others. The color study may result in minor changes andrealignments of all or part of the composition. The artist and coloristshould then decide which color pigments must be acquired.

The CartoonIn creating the cartoons, there is now a return to refined drawing:

charcoal and cont drawings enlarged to the full scale of the finished

fresco. The original compositional drawing, gridded with one-inchsquares, is transferred to large sheets of paper with a one-foot gridpattern (again, a metric configuration may well be preferable). This islaborious and exacting, but results in the ability to view the fullcomposition in terms of proportion and perspective. Relative weightand arrangement of individual elements in the picture can beconfirmed as properly balanced and scaled to each other. Thecartoons may also be mounted at the actual painting site wall toallow the artist line-of-sight references.

Tracing and PunchingMore importantly, the cartoon is a primary gauge used to ensure that

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the accuracy of the original composition is maintained on the wall. Tothis end, semi-transparent tracing paper is laid over the cartoon anddominant lines are traced. The tracing paper is removed and punchedwith a large needle every few inches along the traced lines. Thesetracings are set aside for the sinopia process, and are used again

when painting begins.

Site and Pigment PreparationA short time prior to approaching the wall, scaffolding must be

assembled as needed and grinding tables arranged at the work site.The artist or colorist supervises a team of assistants in preparingmixtures of pigments and distilled water, which will be rendered to abuttery texture by grinding the colors on glass plates with heavystone or glass mullers. To whiten a color, slaked lime itself is oftenused. Mulling is labor intensive even tedious but necessary toensure that pigments and lime crystals are ground finely enough tobe drawn into the porous plaster as it dries.

It is at this point with the colors prepared, the tracings andpunchings completed, and a designated scratch coat area thoroughlymisted with water the night before that the artist and crew areready to approach the wall.

PouncingThe punched tracings, with the essential outline information from the

cartoons, are affixed with string loops and suspended in place on the

wall from nails gently driven into the scratch coat. Small gauze bagsfilled with red earth pigment are tapped pounced over thepunched holes in the tracings to create a dotted outline on thescratch coat.

The SinopiaThe tracings are removed, and with drawings and cartoons mounted

nearby for reference, the artist follows the dotted outline to begin thesinopia, or underdrawing. Though the scratch coat is rough and thedrawing (using red pigment suspended in water) is not particularlydetailed, it once again serves to fix the drawing in the mind and

allows a final confirmation of compositional correctness. The scratchcoat is then heavily misted with distilled water the night beforepainting.

The IntonacoThe muratore, or mason, is then brought in to apply the thin lime

plaster skin over a portion of the sinopia designated by the artist. Thisapplication is referred to as the giornata, figuratively translated aswork that can be done in a day. The muratore is generally directedto extend the fresh plaster lay an inch or so beyond the borders of

the giornata to allow room for the artist to evenly trim the edges afterthe days work.

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This, the final painting surface called the intonaco is an eighth-inch layer of fully slaked lime and sand, mixed one-to-one on-site. Itmust be neither too wet nor too dry for purposes of trowling andpigment absorbency. Moisture content is an inexact science even for

experienced masons and fresco painters, and conditions at each site-- such as thickness and absorbency of the scratch coat, ambientroom heat and humidity, temperature of the exterior of the wall --must be accounted for. The intonaco must be troweled smooth andflat, and checked from various angles for irregularities. Spotapplications of a watery mixture of pure lime can smoothirregularities in overall surface texture.

Assisting the MaestroAs the muratores work is being completed and a second pouncing

onto the intonaco begins, assistants must prepare a table near theintonaco. This table becomes, in essence, the painters palette. On itrests containers often bowls of the ground colors selected for thatday. These colors are suspended in distilled water, and must befrequently stirred or spun by an assistant to maintain suspension ofthe pigments. Also on the table are containers of various sizebrushes, a hand-held palette of mulled color, and several bowls ofclean water for rinsing brushes. An assistant must stand at the readyto hand the painter brushes, damp sponges and maintain thecontainers of fresh water. If satisfied with the pouncing on theintonaco, the artist proceeds, guided by these critical reference

points.

The Golden HourAn indication of the ideal painting surface, called the golden hour,

occurs when paint is immediately absorbed when brushed onto thewall. Viewed at the proper angle to a light source, this effect can beseen clearly as a reflective brushstroke that disappears promptlyupon application. The wall is said to be taking at that point. Shouldthe wall be seen as slow in taking, the wall is too wet, resulting in thebrush picking up smearing or lifting color.

Tearing it OutMistakes cannot be brushed out or covered over, and therein lies the

high challenge of fresco. Errors in laying the plaster, or even painting,may well result in having to scrape off all or part of the intonaco.Variances in color or inappropriate appearances of lime patches andthe like can be corrected by creating a secondary painting surface ofegg tempera one year after the fresco is painted. But even whentaking correctly, the artist generally has a window of only several

hours before the wall begins to lock up, becoming too dry to takepigment properly.

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MistingAs the giornata nears completion, the artist may occasionally direct

that the intonaco be sprayed with a fine mist of water, which acts asa medium to draw pigments further into the wall.

The End of the DayAt the end of each day, a day line must be cut, which consists of

trimming the small amount of excess plaster left by the mason at theedge of the intonaco. The day line should be cut and beveled withfine, sharp and flexible instrument (a utility blade or trowel).Execution must be precise, as other giornatas will be troweledadjacent to all or part of the day line at some point. These newintonacos must be painstakingly married to the previous day line soas to render the borders virtually invisible.

The scratch coat well beyond the giornata is likely to have absorbeda great deal of moisture. Care must be taken not to over-water thescratch coat for the next days painting if the new intonaco is to belaid adjacent to the one prior to it.

Coordination and understanding of the fresco process isfundamental to success. Inspired and informed by a sense ofbeauty; an acutely intimate understanding of thematicresonances; an essentially rote knowledge of every detail of

the composition; a highly-attuned eye for drawing; a fulsomeunderstanding of color; as well as an appreciation forteamwork and the time and effort it has taken to reach thepainting stage, the artists persevere with each days workuntil completion

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Panel painting

The Ghent Altarpiece: The Adoration of the Mystic Lamb, interiorview, 1432. A large panel painting for display behind an altar.

A Panel painting was a painting support medium in popular use inthe West for about 300 years, from the late 12th century until the16th century, after which canvas and oil paint became the norm. A"panel" was created from wood with a chalk mixture layered on top toform a solid, smooth surface, not unlike ivory, and was then paintedusing an egg-yolk based paint. A panel painting would typically bedisplayed inside a churchas an altarpiece, or behind or in front ofthe altar as a visual enhancement to a sermonwhile in later years itwould be integrated into furniture. Along with fresco it was theprimary medium ofGothic painting.

History

Panel painting is very old; we know it existed in Greece and Rome,but very few have survived. It was also important in Byzantine art butagain, few have survived due to the iconoclasm of the 9th century.

In the late 12th century panel painting experienced a revival inWestern Europe because of new liturgical practicesthe priest andcongregation were now on the same side of the altar, leaving thespace behind the altar free for the display of a holy imageand thus

altar decorations were in demand. The earliest forms of panelpainting were dossals (altar backs), altar fronts and crucifixes. Allwere painted with religious images, commonly the Virgin and Child,Christ, Saints.

Italy in the 13th and 14th centuries was the golden age of panelpainting. However, it is estimated that of all the panel paintingsproduced there, 99.9 percent have been lost.

By the 15th century with the appearance of humanism, and achanging attitude about the function of art and patronage, panel

painting went in new directions. Secular art opened the way to thecreation of chests, painted beds, birth trays and other furniture. Theawareness of the importance of the individual gave rise to a newform: the portrait.Panel construction and painting

While popular throughout Western Europe, Italy was where panelpainting flourished. Italians developed a technique for theconstruction that lasted unchanged for over 300 years, until theintroduction of oil paint in the 15th century and the use of canvas in

the 16th century became the norm. The technique is known to usthrough Cennino Cennini's The Craftsman's Handbook (Il libro dell'

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arte) published in 1390. It was a laborious and painstaking process:1 A carpenter would construct a solid wood piece the size of the

panel needed. It was usually seasoned poplar, willow or linden. Itwould be planed and sanded and if needed, joined with otherpieces to obtain the desired size and shape.

2 The wood would be coated with a mixture of animal-skin glues andresin and covered with linen (the mixture and linen combinationwas known as a "size").

3 Once the size had dried, layer upon layer of gesso would beapplied, each layer sanded down before the next applied,sometimes as many as 15 layers, before a smooth hard surfaceemerged, not unlike ivory.

Once the panel construction was complete, the design was laid out incharcoal, making corrections and adjustments, until it reached theartists vision. Then using small brushes dipped in a mixture ofpigment and egg-yolk (known as tempera), the paint was applied invery small strokes. Because tempera dries quickly and is notconducive to mistakes, each stroke was a one-shot chance and had tobe perfect each time. This exacting perfection shaped the nature andstyle of the art produced.

http://www.allaboutall.info/article/Gessohttp://www.allaboutall.info/article/Temperahttp://www.allaboutall.info/article/Gessohttp://www.allaboutall.info/article/Tempera