The Vatican Museums can boast the world’s most beautiful frescoes, but just what is a fresco?

Show Notes

Today we will discuss frescoes, a kind of painting we do not see much anymore, but which was used by the very ancient Greeks, Etruscans, and Romans, and was common in the Renaissance.  But first I’d first like to let you know that I’m changing up the schedule a little bit.

I’ve published full episodes every Tuesday for 45 consecutive weeks and supplemented them with occasional Mini Pods on Thursdays. For the next couple of months, I’m going to reverse this and publish regular Mini Pods, but only occasional full episodes. The reason is simply that a few other things require my attention, and I lack the time to prepare a full episode each week. I need to find a little more time to think things over, and this is a way of getting it.

One of the new demands on my time leaves me excited: I need to get Ready for Rome, where—COVID permitting—I’ll be going in September with several family members. The requirements of planning this trip partially overlap with those of preparing these podcasts, but the tasks are not identical. For example, in preparation for my trip and for seeing some old Italian friends again, I want to spend more time reading and writing Italian than I usually do, but this will make only a minor contribution to these podcasts.

I don’t expect the character of these podcasts to change much, but the mini pods might tilt occasionally in the direction of the practical side of travel to Rome, from which I have so far stayed largely clear. But my group will have to decide soon where to stay, and how to budget our time and money, so it’s possible I’ll learn or relearn something worth sharing.

So that’s it, for the next couple of months expect regular Mini Pods on Thursdays, but only occasional full episodes on Tuesdays.


As for frescoes, we have been talking about them as an important feature of the Vatican Museums, so I want to be more clear about just what they are. We don’t see frescoes very often here in the United States, but they were a characteristic art form of the Renaissance. Mosaics were a characteristic art form of the Middle Ages, at least in Rome, Ravenna, Palermo, Constantinople, and a few other places, but frescoes edged them out in the Renaissance. One feature that frescoes share with the mosaics so typical of the preceding age is that they were made to last. In mosaics and frescoes, the colors are fixed in stone or glass and become part of a wall, so they are protected in ways that paint on canvas or wood is not.

[Here are links for good pages on mosaics in Ravenna: Byzantine Ravenna,    Byzantine Ravenna – S. Vitale

Good pages on mosaics in Palermo: Martorana & Cappella Palatina ]

In Rome, the most highly regarded Renaissance frescoes are those by Michelangelo in the Sistine Chapel and by Raphael in the Raphael Rooms and the Villa Farnesina. There are also good frescoes from the late Renaissance in the Capitoline Museums, which represent decisive scenes from Ancient Roman history. Earlier frescoes by Pietro Cavallini can be seen in Santa Cecelia in Trastevere, and there is a famous baroque fresco in the Barberini Palace by Pietro da Cortona. Beyond Rome, there are highly regarded frescoes in Assisi, Florence, Arezzo, Padua, and elsewhere. To see frescoes left by the ancient Romans, visit Palazzo Massimo near the Termini train station in Rome.

“Fresco” means fresh, and fresh plaster is still wet. Frescoes are painted in wet plaster so the pigments of the paint then become part of the plaster wall as it sets. The obvious challenge to doing this is that the artist must work fast, and—once the plaster has set—he can make no corrections to the fresco properly understood, unless the hardened plaster is gouged out and a new layer of plaster and paint is then applied. Otherwise, frescoists are limited to adding paint over parts of a fresco that has hardened. Thus, for example, when in the Counterreformation it was decided that religious art should not include nude bodies, the Church faced the decision whether to simply paint loincloths over the naked parts of the saints and sinners in Michelangelo’s Last Judgment, or to hack away the plaster and create a new section of fresco altogether. They did a little of both, so some of the loincloths could later be scraped away and the underlying fresco exposed, but in other cases, Michelangelo’s fresco has been replaced, not just covered.

A detail of Michelangelo’s “Last Judgment,” redone by Daniele Volterra (Public domain, via Wikimedia Commons)

This detail from Michelangelo’s Last Judgment was actually redone by Daniele Volterra. It shows St. Blaise, who is holding the iron combs of his martyrdom, and St. Catherine of Alexandria, who is holding the spiked wheel of hers. Michelangelo’s figures had been nude, and too close for the Church’s comfort, so Volterra chiseled them away and added a section of new fresco to the older one.

The durability of a fresco is remarkable, and the key is that wet plaster does not merely dry, it sets. That is, it undergoes a chemical reaction, and becomes—in effect—stone. Stated simply, plaster begins as limestone or marble, which is then cooked in a kiln. The resulting powder is mixed with water, and this paste then dries when it is spread on a wall. Each step results in a chemical reaction, and the final result is calcium carbonite, which is the main ingredient in the marble or limestone we started with. Thus, plaster begins in stone and ends in stone. We call the walls of most modern houses “sheetrock,” but the word “rock” is undeserved. If you want to encounter a really sturdy wall material, look for an old house with plaster, which makes a real sheet of rock, and it is no easy feat to drive a nail into it to hang a picture. Hence it is that there are frescoes in Crete that are 4,000 years old.

So, durability is the most obvious advantage of a fresco. To achieve it, the area to be frescoed had to be covered with a base layer of plaster. This layer, called the arriccio, was usually about ¾ of an inch thick. Its purpose was to smooth over the irregular surface that comes with a stone or brick wall. Then, on each day of painting a slightly thinner layer of finer plaster was added, and it was to this layer—called the intonaco—that the artist would add his paint.

In addition to the downside that mistakes set in stone cannot be corrected, the fresco artist must work fast. Depending on temperature and humidity, he may have twelve hours or less before a new application of intonaco dries. He must first decide on the size and shape of the area to cover with new plaster, and he must then finish painting that section on the day the plaster is troweled into place. Such a section is called a “giornata,” a day’s work, and an expert’s careful examination of a fresco can sometimes map the many giornate required in the painting of an entire fresco.

To help get the general proportions and outlines of a fresco right, the artist would draw what he intended to paint on large sheets of paper, or cartoni, which then got called the “cartoons” of the fresco he would be painting. To transfer the design from the cartoon to the wet plaster, he would have his assistants poke thousands of little holes through the lines he had drawn on it and then put the cartoon up against his wall. They would then tap it repeatedly with little bags of charcoal dust, and the dust would pass though the holes onto the wall and leave the outlines of the shapes in the intonaco. Alternatively, the lines of a cartoon in position could be traced with a stylus, which would leave indentations in the wet plaster just behind the cartoon. Either way, they were just getting started, for pigments had to be mixed, colors brushed on in the right places, details added, and so forth. As someone who cannot even draw a good stick figure, I marvel at the difficulty of painting a fresco, and Michelangelo did it while doing backbends almost 70 feet in the air.

For a short video by NOVA on Michelangelo and his fresco techniche, click here.

Perhaps the most striking thing about the great Renaissance frescoes is their size. They cover vast surfaces with engaging scenes and brilliant colors, and this too adds to their difficulty. That the artists were able to draw their figures to scale, even when these figures were 15 or even 50 feet apart is remarkable, and Michelangelo faced the further challenge of painting on a curved surface.

If you are tolerant of old films and don’t mind a pope who speaks with a strong British accent, you can get a sense of the challenge of fresco painting in The Agony and the Ecstasy. Shot in 1965, it is dramatized account of the political, technical, and artistic challenges Michelangelo faced in the painting of the ceiling of the Sistine Chapel. As well as giving an idea of how frescoes are painted, it’s a decent reminder of other subjects we’ve had on the floor lately, including Michelangelo’s eagerness to be a sculptor, not a painter, the peculiarities of the Warrior Pope, the political threats to the papacy, especially from France, and the rivalry between Michelangelo and Raphael.

On a closing note, lest we think that no one has done large frescoes in recent times,

I stumbled upon some in the Abbey of Monte Cassino, which was mostly destroyed in heavy fighting as the Allies marched up the peninsula in World War II. But the Abbey was rebuilt, and in the 1980’s, an artist named Pietro Annigoni frescoed the large interior dome and the vault of the newly rebuilt church. As I understand it, he died before he could complete the project, and no one has yet been found who is suitable to do so.

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