What is Fresco?

All through the Middles Ages artists painted their pictures directly on the walls of churches.  Their “colors” were ground inorganic matter, such as the semi-precious stone lapis lazuli for blue, or malachite, a copper ore, for green, or earth scooped right out of the ground (sienna, umber, terra verte, Naples yellow).  White was lime and black was charcoal.

To make their colors stick to the wall, they mixed them with eggs—with egg-white, egg-yoke, or both.

An older way was fresco.  They spread a layer of sand mixed with lime over the wall and painted their picture while it was still wet or fresh—fresco in Italian.  With fresco they didn’t need to mix their colors with eggs: plain water was good enough.  It was like water painting: the wall absorbed the paints like modern water-color paper does.  And when it was dry, the colors were somehow (a chemical change) fused with the lime and couldn’t even be rubbed off.


An illustration from  from Techniques of the World’s Great Painters, edited by Waldemar Januszczak, QED Publishing, Ltd., 1980

How to paint in fresco

Preparing the brick or stone wall for the fresco had to be done just right. The painter applied several layers of the lime-and-sand plaster: the first he mixed with rough sand and maybe ground brick; the second with sifted sand; and the third, the layer that had to be smoothest—the one he would paint on—he mixed with his finest sand.

Cracks would appear if the lime and sand mixture was too thick; a mold would form on the surface of the picture if the wall stayed damp or if there were certain chemicals in the water. Condivi tells how Michelangelo fought with these problems and was so discouraged that he wanted to give up painting the Sistine Chapel:

“…in the midst of all this, he was not without anxieties because, when he had begun the work and completed the picture of The Flood, it began to mildew so that the figures could barely be distinguished.  Therefore Michelangelo, reckoning that this must be a sufficient excuse for him to escape such a burden, went to the pope and said to him, “Indeed, I told Your Holiness that this is not my art; what I have done is spoiled.  And if you do not believe it, send someone to see.”  The pope sent San Gallo, who, when he saw it, realized that Michelangelo had applied the plaster too wet, and consequently the dampness coming through produced that effect; and, when Michelangelo had been advised of this, he was forced to continue, and no excuse served.”  (Condivi, Life of Michelangelo)

You have to work fast when painting fresco—that is one of its peculiarities.  You must finish your picture before the lime sets up, which will happen in only a few hours.  That means you have to plan your work carefully: divide the wall up into sections only as large as you can finish in a day.

And you must know exactly what you will paint: there is no time to consider changes as you work.  This is what the cartoons are: your full-size versions on cloth or paper of the wall-paintings.  You draw these at home or in your workshop.  Then you carry them to the church or wherever you are working, and haul them up the scaffold. As soon as you have applied the last layer of lime on the wall, you spread the cartoon over it, tack it to the plaster, and trace its outlines—scratch them right into the surface of your fresco with a stylus.

Here in this close-up of Michelangelo’s famous Adam the stylus grooves are clearly visible in the eye-brows, eyes, nostrils, hair-line,  and collarbone.


(See the comments to this post, especially those by an expert fresco painter.)

The painter carefully trims the edges of his plaster each day; but as there is no way of blending the new day’s lime with the old, a seam between them is always visible; and so, by these seams, you know how many days it took him to paint the fresco, and just what he painted on what day.
Michelangelo’s Delphic Sybil was painted in six days, according to a study of the divisions shown in this diagram, published in La obra píctorica completa de Miguel Angel in the Clásicos del arte series, Noguer-Rizzoli editores.



The black lines show the limits of each day’s plaster (each day’s work).  The dashed lines were traced into the wet plaster as general guidelines. The crosses show where Michelangelo hammered in nails to hold his cartoon while he traced it on the plaster.
He painted the Sybil’s head and some of the background on one day; her arm on the next, and so on. Did he spend a whole day on that single little foot?  Maybe he was dissatisfied with the first one he or a helper had painted, and did it over.

After a fresco is finished it can be touched up with the other method of painting: mixing your colors with eggs (called tempera).  Michelangelo did this here and there, and meant to do more; but Pope Julius was too impatient to wait for him to finish the ceiling as he wanted and ordered him to take the scaffolding down and open the chapel to the public.

“What was lacking,” says Condivi, “was the retouching of the work a secco (Italian for “dry”, the opposite of fresco.  It is the painting you do after the plaster has dried) with ultramarine and in a few places with gold, to give it a richer appearance.  Julius, when the heat of his enthusiasm had subsided, really wanted Michelangelo to furnish these touches; but when Michelangelo thought about the trouble it would give him to reassemble the scaffolding, he answered that what was lacking was nothing of importance.  ‘It really ought to be retouched with gold,’ answered the Pope, to whom Michelangelo responded with the familiarity which was his way with His Holiness, ‘I do not see that men wear gold.’
The Pope said, ‘It will look poor.’
Michelangelo rejoined, ‘Those who are depicted there, they were poor too.’
So he remarked in jest, and so the work has remained.”


This entry was posted in art, art history, fresco painting, great artists, Michelangelo, Pope Julius II, Renaissance, Sistine Chapel and tagged , , , , , . Bookmark the permalink.

36 Responses to What is Fresco?

  1. You have skipped the ‘Sinopia’ step (an underdrawing in red ochre, sometimes quite complete and detailed, on the arriccio layer; that is, under the final smooth plaster layer). Do you know if Michelangelo omitted this preparatory sketch? Or have we just never removed a Michelangelo fresco from its supporting wall? — that is, as far as I know, the only way to confirm the presence of Sinopie. There is an entire museum in Pisa (Museo delle Sinopie) dedicated to these often extraordinary drawings.

    • 100swallows says:

      Thanks, Judith. I left it out to simplify. I can never decide how much detail to go into. But I would suppose that Michelangelo skipped the sinopia step because he used cartoons,which he traced on the wet plaster. The careful sinopia drawing was typical of the old method, wasn’t it? Cennini doesn’t even mention cartoons in his treatise on fresco painting.

      That Museo delle Sinopie sounds fascinating.

  2. I wonder if it is, in fact, an earlier method. Sinopia certainly continued through the 15th C — but was it then replaced by cartoons? Hmmm.

    Anyway, the Museum is fascinating. If you love frescoes, this is surely worth a trip (and then, of course, a visit to the Camposanto Monumentale opposite the Museum, where the sinopie originally came from). I can’t find much in English in a quick search but you’ll get the gist of this Italian article, I’m sure: = Museo delle Sinopie

    • 100swallows says:

      Thanks for the link, Judith. I imagine the name (technique) came from Turkey because Byzantine artisans brought it over to Italy, right?

    • 100swallows says:

      A note to explain the step of fresco painting I left out in my post. The traditional job was done this way:
      The painter applied a layer (or two, or three) to the bare stone or brick wall. The Italians called this layer the arriccio.
      On that layer, while it was still damp, he painted the main lines of his composition in red ocre, sometimes in considerable detail. This step was called the sinopia, the same name as the red earth of the ocre.
      On top of THAT, he spread the final thin layer of fine lime and sand, called the intonaco, for his painting. This final layer was thin enough, transparent enough, to let him see the red ocre drawing underneath.
      Michelangelo skipped the sinopia step. Instead, he made a detailed preliminary sketch on paper (the cartoon), tacked it on top of his final layer before painting, and traced its lines in the soft plaster with a stylus.

  3. Rich says:

    Now I know even better how a fresco works, Swallows.

    But seeing how you traced the day-by-day progress by Mike the angel or Mike the titan, I was asking myself: Where was the main work done? In the cartoons?
    Because the wonderful Delphic Sybil comparted looks a bit like drawing by numbers. Of course it was the hardest work one could imagine. You described it so vividly, those endless days on the scaffold.
    But on the other hand wasn’t it somehow kind of a copy-shop work? Those cartoons already existed and had been worked out. Guess they certainly were not rough sketches.
    I’m at a loss.

    • 100swallows says:

      Rich: Look closely at the stylus grooves in the Adam. They were only rough tracings. Clearly Michelangelo made a new version of what was on the cartoon. But that was certainly detailed too, and colored (in watercolors). It had to be a perfect guide–there was no time to experiment on the fresh plaster before it dried. OK–it was a copy; but a freehand copy that looked different in its new context and had to be modified here and there. As far as I know no cartoons from the ceiling frescoes survive but there are a few around from the Pauline Chapel ones. I’ll see if I can find a picture of one tomorrow.

      • 100swallows says:

        Rich: This is a fragment (263 X 156 cm) of Michelangelo’s cartoon for a part of the Crucifixion of St. Peter fresco in the Vatican.

        It is composed of nineteen sheets of paper, now glued to cloth. The drawing is in charcoal, colored with watercolors. It is in bad condition but you can see quite a few differences with the figures in the fresco. In fact, these cartoon drawings look even better, just as pen-and-ink bozzettos often surpass the final painting they served. (Exhibited in the Capodimonte Galleries of Naples).

  4. wrjones says:

    And I thought painting a 9″ x 12″ canvas was a lot of work. This fresco stuff is very unappealing as a career.

    • 100swallows says:

      Bill: Ceiling painting is admittedly for the birds. But I’m sure a veteran painter like you can get excited over a wall project. Of course nowadays everyone just paints on any old wall with acrylic paints–fresco is out. The thing is, nothing else looks quite like fresco.

  5. kimiam says:

    I don’t know about that. This post makes me want to run out and paint a fresco right now…this and I was asked to team teach a unit on Pompeii recently for a children’s camp. The prep for that…it’s got me thinking about frescoes. I definitely do not want to paint a fresco ceiling, though.

    • 100swallows says:

      Kimiam: I’m like you–I get excited just thinking about doing it. Though not a ceiling, thank you. A good wall at a comfortable height is fine. If you want to experiment with painting with those earth colors and water, you needn’t go through all the steps. Just whitewash a wall and paint right on the lime wet or dry and you have if not a fresco something that looks the same. And to erase it, just slop another coat of slaked lime over it and you have a clean, suggestive wall for your next mural.

      I don’t know if lime is easily available there anymore. Here it is still used in many of the villages. They whitewash the houses inside and out every spring. The lime comes in clumps or powder and when you put it in water it bubbles up and gets hot. When it cools down you can start to paint with it. That slaked lime is also the brilliant white of your palette.
      Good luck. I painted a big bull on the wall of my bedroom years ago and it is still there as far as I know, big and bright as ever.

  6. Fascinating. Somehow I had the impression that “Mike the Angel” (love that) used a pounce wheel and pounced the pattern through the cartoons. Perhaps I saw this in a movie? Thanks for correcting my mis-impression.

    Also, I wonder at the nails used to hold the cartoons. I can imagine plaster flaking off followed by profane cursing in the chapel!

    • 100swallows says:

      Thanks, Todd. Would you believe I never thought of that “Mike the Angel”? And in Spanish it should easily have suggested itself: his name is Miguel Angel!

      I wondered about those nails too. You’d think there was a less destructive way to stick the cartoon to the plaster. Swearing in the chapel? You bet.

  7. Rich says:

    Thanks for the link, Swallows. I just adored the group on this cartoon.
    As you hinted at the difference of the cartoon with the figures in the final fresco – so the term “copy” is futile. It’s just never ending creation.
    How about the cartoons themselves? Were they themselves preceded by studies from the model? How many steps were there from the Idea to the final result?
    A tremendous task in any case!

    • 100swallows says:

      Rich: You come up with some good ones! Did Mike have models? He must have. No one knows the body so completely by heart from all angles. Of course his figures don’t look like any particular model, do they? He stylized them all. He would have tacked the cartoon to the wall and drawn them one after another in his studio (if the wall was high enough there for his twelve foot Prophets!) There are preparatory charcoal drawings of some of the figures and some parts of the figures. That must have been the first step. Then to the cartoon. Coloring was last. Then to the chapel.

  8. erikatakacs says:

    When I was a kid I saw how they mix the lime powder with water. But only realised now it’s the same stuff they use for frescoes. They would dig a hole, dump a big bag of powder, then pour water from buckets and mix with wooden sticks. Kids weren’t allowed too close of course as an accidental fall into the lime pit would have meant burning to death. That’s what I was told anyway. But I liked to watch the bubbles from the chemical reaction. My dad still likes to use whitewash instead of paint in his apartment. And yes, he paints the inside and outside of the old house with this stuff every year.
    Thanks for all the info about frescoes and lime.

    • 100swallows says:

      Erika: If you try to dissolve the lime in a plastic bucket, as I did the first time, it will “burn” a hole in it.
      Remember that lime and sand was the standard cement for centuries. The stones of castles are stuck together with that mix, which gets very hard. General use of Portland cement started here (and in most countries) only around the middle of the twentieth century. The poured concrete bunkers from the Spanish Civil War are the first constructions here with that new cement. Before that all building was down with lime, gypsum, or adobe. The red earth sinopia that Judith mentioned was used around here until recently for many things. Stonemasons used it to mark their boulders, carpenters used it. They still use it to mark the limit for the picador’s horse in the bullring.

      You saw how radiant a freshly limed (whitewashed) house looks. It beats common plastic paint, though it isn’t washable. It is the perfect paint for adobe because it levels the irregularities and fills in the cracks and forms a thin, hard shell over the wall, sealing it from the rain.

  9. erikatakacs says:

    The cement you mention, is the same as mortar? What about concrete? I’m not sure about the differences.
    Yes, I remember how beautiful those whitewashed houses were, with lots of red flowers in the windows! You made me homesick now…

    • 100swallows says:

      Erika: I know this is confusing. Mortar is the mix used to bind bricks or stones together. It can be lime and sand or Portland cement and sand. Portland cement is that gray material now used instead of lime. It was invented in the eighteenth century (or thereabouts).

      Plaster is both the raw material gypsum and a general word for a layer of it or a mix of sand and lime that you spread on a wall.

      Concrete is a mix of lime and sand, or Portland cement and sand, plus gravel. It is poured into forms. The Romans were the first to use it extensively. The dome of the Pantheon in Rome is poured concrete. They added a volcanic ash to it, pozzolana, and it hardened even UNDER WATER, so it was used for bridge piles. Nowadays engineers pour the concrete into forms with metal rods in them. That is called reinforced concrete.

  10. Swallow,

    Who is the author of La obra píctorica completa de Miguel Angel? I’d like to look up this work in Italian or English because I’m very interested in how the author used the plaster seams to calculate how much was painted each day and how long each scene took.

    Thanks in advance, Judith

    • 100swallows says:

      Judith: The author is Ettore Camesasca. I don’t know if the series ever came out in English. The copyright is Rizzoli Editore, Milano, 1966. Camesasca includes several illustrations of Sistine and Pauline fresco figures with black lines to show the plaster seams but he doesn’t say how he decides that one or the other fragment is by Michelangelo or a helper (let alone which helper). You can find a good explanation of fresco giornatas in Waldemar Januszczak’s Techniques of the World’s Great Painters, QED Publishing Limited. 1980. He illustrates with Giotto’s Nativity fresco in Padua.

  11. Got it, thanks:

    The Complete Paintings of Michelangelo
    by Ettore Camesasca
    ISBN 0297761129 / 9780297761129 / 0-297-76112-9
    Publisher Orion Publishing Group, Limited.

    I’ll check Januszczak, too.

  12. Fresco says:

    Sinopia is needed to align the cartoon from painted to unpainted area (with sinopia and the grid) over the plastered area (giornata).

    The one can, in theory use the grid along, but that would be like “painting with one eye closed” – unnecessary complication. Making sinopia also lets the painter to “warm up” for the painting as well as see and present the whole composition on the wall to the patron.

    • 100swallows says:

      Fresco: Thanks for the comment from an experienced fresco artist. Why do you think Michelangelo skipped the sinopia step for his Sistine frescoes and opted for the apparently more clumsy use of cartoons (I mean the problems of nailing them in place, scratching through them, or poking holes and powdering through the holes. etc.)? I would guess it was because his figures were so complex that he wanted a good reference, complete with colors, while he worked–no time to fool around experimenting. But some of those old frescoes done with sinopia were complex too. Did Botticelli use cartoons in the Sistine?

      • Fresco says:

        He did not skip sinopia – sinopia does not replace cartoon and cartoon does not replace sinopia. for the best result the one needs to use both.

        cartoon makes it easier to transfer daily sections (giornatas) providing an outline (after it pricked with needle along the lines and dusted with charcoal or terra-verde pigment which lightens when dry and not so easily spotted afterwards unlike charcoal), but the one still needs the sinopia to align the sections of the cartoon.

        it is virtually impossible to transfer the proper perspective to the large wall without cartoon or projector (for the sake of this conversation lets drop projector:

        For a small painting the one can simply redraw the perspective – on a large wall it is not possible without a small study and later enlargement/transfer through the use of grid. The birth of the renaissance was the invention of the perspective that required grid and cartoon to be transferred exactly and not “freehanded”. Cartoons and templates were used since much earlier – Egypt for example or Imperial Rome, but the invention of the perspective draw such attention to the required foundational step in image transfer and enlargement.

        In addition – every professional mural or element of decor employs “cartoon” – this is a fact, if it is done without cartoon it is the work of an amateur or it is a painting loosely referred to as “fine art”.

        • Fresco says:

          to paint a mural/wall painting the one needs to transfer the small rendering onto a wall at full scale prior to painting.
          Then the artist can proceed with actual painting (coloring) of the transferred design – this actually is the “sinopia” or underpainting/under drawing.

          It is referred to as Sinopia because the cheapest red oxide used to create it was mined at the town of Sinopia (Turkey).

          in fresco this “original transfer” gets covered with plaster one small section at the time. So cartoons used to transfer it to the wall are reused again after the plaster is applied.

          the reason it is looks confusing is the fact that historians are not aware of the routine technique details and often omit important steps because they are not evident and a lot is based on assumptions and educated guesses. the problem is that the one needs to practice the technique to understand/discover subtle details or real value of “seemingly unimportant” or “redundant” steps.

          it is often possible to assemble a fairly accurate general outline using different sources and references, but it would never be complete without actual professional (not experimental) practice.

          • Fresco says:

            in “pre-perspective” era precision was needed only to transfer geometric decorative details and ornaments so sinopia (underpainting) was often freehanded. also for a fresco that was also an efficient way to quickly design and present the composition in a full scale to the patron. if changes were needed artist will simply whitewash the rejected parts and sketch over the corrections.

            the sequence was:

            1 – small sketch
            2 – full scale monochrome rendition (sinopia)
            3 – corrected/changed parts re-sketched for future reference
            4 – painting section by section using latest reference sketches

            renaissance and Contemporary sequence:

            1 – small sketch
            2 – detailed renderings – corrected changed parts redrawn
            3 – detailed cartoons/full scale drawings
            4 – cartoon transfer to wall – entire composition – full scale monochrome rendition – sinopia (for dry mediums – under drawing)
            5 – cartoon transfer over fresh plaster one section at the time (for dry mediums – painting whole over the underdrawing from step 4)

            i hope that helps ;)

            • 100swallows says:

              Fresco: Thank you very much for your explanation. Yes, it helps. So Michelangelo used the sinopia step AND the cartoon. And now I understand why the cartoon wasn’t necessary in, for example, Cennini’s (or Giotto’s) time. But you’d think they would have appreciated cartoons too, even if they meant more work and hassle, because of the greater precision. Each day they had to re-draw, freehand, on the fresh plaster, the segment of their sinopia wall painting which they had just covered up, right?

              • Fresco says:

                That is correct. I think that they did have some forms of cartoon (drawing reference) but were not aware of the advanced elements of perspective therefore “eyeballing” was enough. Actually i remember in some reference documents I found that there was a “split” between “purists” and “cheaters” where cheaters were artists that adopted grid transfer. Purists were arguing that they (cheaters) did it due to the inferior drafting skills…

  13. Hello, if anyone is interested I am a fresco artist and have created a video called “What is Fresco?” for my collectors. You can see it on my website or directly on you tube at http://www.youtube.com/watch?v=-prAIz0urTE

    • 100swallows says:

      Liana Sofia Tumino:Thank you very much. I was very interested and went over to your blog to have a look, then had a hard time leaving it. Those are excellent videos and I learned a lot. I had never understood how they were able to transfer frescoes to canvas, for instance. The video on Italy was also really well-made. The short scenes seemed like flashes of beautiful memories in a dream. I wonder how long it took you to become such a skillful fresco painter.

      • Thank you, sorry for the delay in replying but I didn’t see your response until now!? I have been painting in fresco for almost 18 years and I still seem to learn something with every single one!! It is a journey for sure and I am so glad that people like you are interested in keeping it alive! Thank you again for the kind words I am so glad you enjoyed the videos and that they may have helped you understand fresco better. Cheers, Liana.

  14. I’ve been trained as a professional artist in Italy and currently I run a studio in San Francisco where I am an instructor at the Academy of Art College. There is a great difference between an ‘affresco’ and a generic ‘mural’ that can be acrilic or tempera. ‘Fresco’ is a very simple but extremely precious tecnique.I heard people calling a ‘fresco’ the Leonardo’s "Last Supper" wich is not. The Leonardo’s painting is a ‘tempera’, for that reason it did not last.The real ‘fresco’ last practically for ever (look the great ‘fresco’ painters like Michelangelo, Raffaello, etc. Their works still shine after centuries). Anyway, this book gives clear and unmistakable instructions to everyone who wants to learn this fascinating tecnique.Well done! By the way:knowing how the great masters did their work does not means automatically joining the Club. Got it?

  15. Georgio says:

    We (my wife and I) just saw Michelangelo’s Cistine chapel creations today in Rome and so appreciate the article and informative comments. Perhaps an artist , musician or poet should appreciate more than anyone else that humanity has been created in the likeness of God. Thank you for your contributions everyone.

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