12 March 2006

Michelangelo’s Lost Three-Dimensional “Sketches”

The historical Michelangelo Drawings exhibition (British Museum through 25 June) gives a sense of seeing the artist at work, of watching masterpieces take shape from the most humble beginnings. This feeling is perhaps justified, because drawing was an essential tool for Michelangelo’s preparation of larger works. And yet, before jumping to conclusions about what his drawings tell us, it is critical to realize that there was another type of preparatory “sketch” that Michelangelo used: his small three-dimensional figure models. These models are almost entirely lost 1, and it is easy to overlook their importance. But they probably played as critical a role in Michelangelo’s creative process as drawing on paper. By ignoring how this class of work relates to the drawings, which the Michelangelo Drawings exhibition for the most part does, it becomes impossible to reach a full understanding of how Michelangelo worked; it is difficult to say with confidence what were the purposes, or even the subjects, of some of his best drawings.

Any doubts about the importance of the preparatory model are dispelled by Michelangelo’s own words in one of his sonnets:

When divine Art conceives a form or face,
She bids the craftsman for his first essay
To shape a simple model in mere clay:
This is the earliest birth of Art’s embrace.

In these lines Michelangelo describes forming a clay model as preparation for carving a marble sculpture. His celebration of the humble medium of clay should not to be dismissed as poetic license, because he wrote from his own experience. Michelangelo’s clay models must have been remarkable sculptures in their own right; most likely they rivaled the beauty of his drawings on paper. A clay model attribute to Michelangelo is show in the left column.

Despite the survival of a few models of questionable authenticity, for the most part the lost clay models cannot speak to us or inform our understanding, unless we can find some further trace of them. The colossal marble sculpture does not easily reveal to the imagination its humble origins of clay 2.

But where to search for the lost models? As I said above, the Michelangelo Drawings exhibition gives a sense of seeing the master at work. If there is any real basis to this impression, if the drawings really do provide a picture of how Michelangelo worked, then the place to search for the lost clay models is in the drawings themselves. Of course, the impression of “seeing the master at work” from the drawings might be an illusion. But as we shall see, Michelangelo’s drawings will not leave us disappointed in the quest to rediscover the lost models.

Michelangelo’s Drawings and the Three Elements:
Imagination, Reality, and Style

Although Michelangelo’s finished masterpieces are impressive for their awesome dimensions, he confronted his core creative challenges at a smaller scale; the lines from the sonnet quoted above make this clear. But reducing the scale of an artwork does not in itself simplify the complexity of its content. Even working on a small scale, an ambitious artist like Michelangelo had to confront a daunting challenge of combining three distinct elements: the freedom of his imagination, the constraints of realistic form, and the interpretation of style.

While the still-life painter or the abstract painter can in part escape these challenges by abandoning imagination, in the first case, or the constraints of depicting reality, in the second, Michelangelo confronted the full challenge of bringing together these three elements of art. And yet there is every indication that he did so not in a wild, reckless, or heroic manner; but rather, that he used a systematic approach, divided his problems into parts, and created a successful fusion using his deliberate preparations.

To see the evidence of this in the Michelangelo Drawings exhibition, we can look at 1) drawings which are clearly made from imagination, 2) drawings that are non-idealized studies of the living or dead human bodies, and 3) drawings connected to the stylistic content of ancient sculpture.

Drawing from Imagination

A rudimentary compositional sketch for the Judith and Holofernes scene in the Sistine Chapel (see left column) contains little sense of realism or style. It is a pure work of imagination, an early statement of what the final fresco scene should contain. Perhaps it is nothing more than a sort of visual shopping list, making a record of what will be needed, with an approximate location for each figure. It is not an especially good drawing, but it was probably in some way useful to Michelangelo, and to us it provides valuable information. We see that Michelangelo’s artworks could grow from the most humble imaginary beginnings.

Drawings of Realistic Human Form

Some of Michelangelo’s least artistic drawings are those in which he seems to make a faithful record of what he saw. For example, he made brown pen and ink drawings of the arm muscles of a flayed corpse, diagrams full of information, but of little immediate aesthetic value [Studies of flayed arms, (left column)]. Here we see Michelangelo collecting data on human form, but not idealizing or interpreting it immediately. The data is left in a raw form. This does not make for the most interesting picture, but as a faithful record, this anatomical data could serve him in later work.

Another example of Michelangelo working, apparently with an effort to record realistic form, is in a drawing of two male heads [Two heads, right column)]. The faces depicted here have a sense of realism, a prosaic quality of everyday life. The faces are not idealized or heroic, they are quite unlike what we think of as Michelangelo’s artistic vision of man. And yet, as faithful records, like the anatomical data, they could serve as a basis for later work.

The drawings of realistic form not only show a dispassionate side of the fiery-tempered Michelangelo. They also show him dividing his problem into parts literally, by using separate studies for different parts of the body.

Drawings from Ancient Sculpture

Michelangelo made extensive drawing studies of ancient Roman marble sculptures. It is clear that he was interested in the poses of the figures, but perhaps even more in their style. Unfortunately, the Michelangelo Drawings exhibition does not contain drawings of ancient sculpture that are obviously made directly from sculpture itself, although such drawings exist. But his experimentation with drawing variations on the pose of the ancient Apollo Belvedere sculpture [e.g., left column, A group of three nude men; right column, A youth beckoning] show evidence, within the exhibition itself, of his fascination with ancient sculpture pose and style. Here is evidence of the proud Michelangelo borrowing the ideas of other artists.

In the drawings described above we have seen Michelangelo at work with the three elements: the imaginary, the realistic, and the stylistic. Although these are perhaps mediocre from an artistic standpoint, this does not detract from their importance. These drawings show how Michelangelo studied each of the three elements of art, to some degree in isolation, in much the same way that he sometimes studied different parts of the body in separate drawing studies. Michelangelo’s great masterpieces did not arise in a single step, like God’s creation of Adam as described in Genesis. Rather, as the drawings discussed above show, he built, or at least had the option to build, his complex artistic world from the simplest elements.

Bringing the Elements Together:
Drawings for the Sistine Chapel Ceiling Frescoes

Michelangelo’s great challenge, of course, was to combine the three elements, imagination, reality, and style. The fact that he studied each in isolation (too some degree) implies that when he wished to bring these elements together, he could do so using the results of his separate studies, using his own drawings as data. When he brought these elements together in drawing, he produced rich artworks; but these drawings are inherently more difficult to classify into the elementary categories that have been discussed above.

Perhaps the most beautiful and ambiguous of Michelangelo’s surviving drawings are his magnificent red chalk works for the Sistine Chapel ceiling, listed below:

Study for a seated male nude (left column)

Study for Adam (left column)

Studies for Haman (right column)

Studies for the Crucifixion of Haman (right column)

I will refer to these as “the red chalk drawings”. These drawings have the following in common:

1) each contains a remarkable representation of male human form;

2) each is closely related to the appearance of the figures in the ceiling frescoes;

3) each is a highly refined drawing with rich anatomical detail;

4) each shows an incomplete figure, with the representation of the body divided into parts, not necessarily consistent in scale;

5) the poses are heroic in character, poses which would be uncomfortable, or impossible, for a live model to maintain for a sustained length of time;

6) the figures do not look like ordinary people, but like ideal human forms, with style clearly related to, but still distinct from, ancient Greek and Roman sculpture.

Together these common qualities point to the drawings not being merely pure works of imagination, studies from reality, or quotations from ancient sculpture. Rather, their common qualities show that the drawings are a synthesis combing all three elements. How then should we answer the simplest of questions: who, or what, were the subjects for these drawings?

The Michelangelo Drawings exhibition provides a definitive answer — these red chalk drawings are studies of live human models. This is stated as a “fact” by British Museum drawings curator Hugo Chapman 3 in the volume that accompanies the exhibition. Although the makers of the exhibition recognize that Michelangelo has brought together the three distinct artistic elements in these drawings, they fail to follow the line of reasoning to the logical conclusion. How can the exhibition be so certain that Michelangelo drew these figures from life?

Is it not equally likely that these magnificent drawings are in fact depictions of small clay models? 4

The functional connection between 3-dimensional and 2-dimensional artworks

Although he does not mention it in the sonnet quoted above, we know that Michelangelo used drawing as an aide in making sculpture. That is to say, Michelangelo used 2-dimensional drawings, such as the remarkable studies for the figure of ‘Day’ to guide in the creation of 3-dimensional physical form. But conversely, sculpture has been equally valuable for making drawings; that is to say, using the 3-dimensional to create the 2-dimensional. We have already seen one aspect of this in Michelangelo’s use of ancient sculpture. But drawing from ancient sculpture has the inherent limitation that one must accept the 3-dimensional sculpture as one finds it.

Another approach, which gives more flexibility to the artist, is described by Cennino Cennini in his “Il Libra dell’Arte”, written perhaps in the 1390’s. After describing drawing and painting techniques in great detail, Cennini in the final section of his book writes “I will tell you about something else which is very useful and gets you great reputation in drawing, for copying and imitating things from nature: and it is called casting.” 5 Cennini proceeds to explain how to make life-casts of human faces and complete figures, using plaster of Paris.

Life-casting is a simple way to make realistic sculpture (left column). Cennini makes it clear that an artist, without possessing the skills of a sculptor, can create life-like three-dimensional forms; these forms he can draw or paint at his leisure to create a result that seems to have been made from life, without the disadvantages of working from a restless human model. The implications of Cennini’s writing are profound. They suggest that whenever we see any portrait or figure in an old painting or drawing, we must consider the possibility that we are in fact looking at an image of a life-cast, not a living person. This was perhaps standard practice.

Of course, life-casting also has limitations. The artist can only make a life-cast from a real person, and must accept the person as he finds him. The life-cast will be life-sized, and thus unwieldy and heavy. But if the artist possesses the skills of the sculptor, he can make his own life-like forms to draw. Michelangelo, one of the greatest sculptors and draftsmen of all time, had a unique opportunity to create life-like models, and to draw them so that they looked alive. This I propose is precisely what he did with the Sistine Chapel red chalk drawings listed above. These drawings thus could rescue from oblivion some of Michelangelo’s lost 3-dimensional “sketches”. If we take another look at the clay torso model show earlier with more dramatic lighting (right column) we can see how inviting a subject for drawing these models could have been. Whether this particular model is an authentic Michelangelo is to some degree irrelevant; we only need to look at it as an example of what Michelangelo could have made, and could have drawn.

Although there is not any question that Michelangelo could have done this, it would seem to represent extra work in the context of a project like frescoing the Sistine Chapel. From Michelangelo’s drawings it is clear that he was not prone to do extra or unnecessary labor. For example, in a refined drawing of a figure, he would typically leave a hand or arm in rough schematic form, if he knew that these body parts would be invisible in the finished artwork. Thus, to support my interpretation, it is necessary for me to describe some very solid advantages that Michelangelo would receive from the labor of making clay models for his figures.

Purposes for making 3-dimensional models, when a 2-dimensional image is the goal

There are three distinct reasons for creating clay models for the Sistine chapel figures.

The first reason relates to the three elements of art that we discussed above. If Michelangelo made a design from his imagination, if he had realistic life-studies of human models to serve as data, and if he had a deep understanding of ancient sculptural style, he nonetheless still had a huge challenge to combine these three elements. The Michelangelo Drawings exhibition, by proposing that the red chalk drawings are life studies, puts the enormous burden on Michelangelo of combining the three elements while looking at a live model, a figure most likely not of the ideal form that he desired for his artwork. But if instead Michelangelo integrated the three elements into a clay model, as I propose, he could work at leisure to create precisely the ideal human form that he desired — in much the same way we know he did when preparing to carve a marble sculpture 6. If Michelangelo’s live model for Adam were an old man with pot-belly, he could nonetheless transform that figure into an ideal form in clay 7. He could copy a head from an ancient sculpture if the live model’s head did not satisfy. In sum, the clay model presents the ideal medium for Michelangelo to bring together the three elements, imagination, reality, and style. To do so while drawing a figure from life is possible, but it would be far more difficult, unless the figure already had something approaching the ideal form.

The second reason the clay models would be useful is because of their rigid physical stability. Michelangelo was interested in depicting the most heroic and difficult poses. By making clay models, he could turn life into still-life, and draw at leisure — just as Cennini describes with the life-casts. Drawing from the clay is the optimal condition for making drawings as refined as the red chalk drawings. Attempting to produce a refined result when drawing a live model, a person perhaps trembling from the strain of the pose, would be far more difficult and frustrating.

As the first two reasons make clear, creating clay models, which might at first seem like extra work, would in fact ease Michelangelo’s creative burden. For these two reasons alone, my interpretation of the red chalk drawings, as depictions of clay models rather than live models, is justified. For these two reasons, we can be skeptical of the exhibition’s certain claim that these are life studies. As we shall now see, the third reason for making the clay sculptures is that they allow for a simple solution to one of the most difficult aspects of the fresco project: getting the figures onto the Sistine Chapel ceiling.

The Most Important Advantage of Using 3-Dimensional Models in Creating the Ceiling Frescoes

Candlelight in the Chapel

Whether Michelangelo’s drawings are from life or from clay models, the artist faced a number of problems in putting them on the Sistine Chapel ceiling. For one thing, he would have to enlarge them. Normally when artists enlarged a drawing, they drew a system of square grids on their drawing, then drew a larger system of grids on the surface to be painted, such as a panel, a canvas, or a wall. They could then enlarge the drawing by comparing the grids. This type of enlargement is so simple that it could safely be left to assistants. However, there are no such grids on the surviving drawings for the Sistine Chapel ceiling. At first this might seem mysterious. However, there is a good reason that there are no grids on the drawings: grid enlargement would not have helped Michelangelo to transfer his drawings to the ceiling 8.

The reason that grid enlargement would have been of no help is that the Sistine chapel ceiling is not a flat surface; rather, it consists of many curving surfaces. The grid method would not give the correct perspective for enlarging the figures from normal drawings onto these curved surfaces. To transform a flat drawing onto a curved surface, but retain the correct perspective and foreshortening of the figures, represents a major computational headache. The task is complex because it is necessary to take into consideration both the curvature of the wall and the physical structure of the figure in the drawing. For example, there are places in the Chapel where the wall curves forward, but the figure leans backward; both factors need to be taken into consideration to produce the correct perspective. Today we could use a computer for the task. To do it without a computer would require extensive computation by hand, no evidence of which exists. How did Michelangelo do it then? The solution may be this: although it is difficult to enlarge a drawing, such as that of the foreshortened figure Haman, onto a curving ceiling, if, on the other hand, one has a three-dimensional model of the figure, the process becomes trivial. All that is necessary is to arrange the figure in the correct pose (perhaps suspending it with string, or supporting it with rods), and then use a candle to cast a shadow of the clay model onto the curving ceiling. The enlargement and the correction for the curvature happen automatically (see examples in left and right columns). With a computer today we could simulate this process with a virtual model of the figure, the wall, and the candle, if no real three-dimensional model were available.

We see then that Michelangelo would have a major incentive to create clay models of his figures, in order to get them onto the ceiling in the correct perspective — if he discovered the shadow projection technique.

It could be objected that the sheer scale of the Sistine chapel, combined with the particular structure of the scaffold used by Michelangelo to reach the ceiling, might make it impossible to project clay models onto the ceiling as I describe. This technical objection might very well be valid. It all depends on the size of the clay models, the nature and strength of the light source, and the exact structure of the scaffold. However, this technical objection is in no way fatal to my argument. If Michelangelo were for technical reasons unable to implement this scheme in the chapel itself, he could have achieved the same result by projecting the shadows of clay models onto a simple model of the Sistine Chapel ceiling 9. Enlarging these projections to the chapel itself would be a trivial matter of increasing the scale; the simple grid method would work (see examples in left and right columns).

I have given three reasons for making the clay models. Michelangelo might have initially made them for only the first two reasons. Having the clay models on the scaffold, he might have observed the effects of shadow enlargement by accident. But with the clay models ready, he could easily take advantage of the discovery.

Of course the candle projection would give a result that was perfect for only one viewpoint (in this case at the position of the candle). But this is a general limitation of all perspective projections, for paintings on flat as well as curved surfaces. Whatever method Michelangelo used, it would always have this drawback. This is inherent limitation of representing 3-dimensional form or a 2-dimensional surface, whether flat or curved.

From Shadow to Fresco

The method of casting a shadow on the chapel ceiling (or a model ceiling) would give the outline, or silhouette of the clay model, but not any of the other internal features — in the same way that our own shadows delineate our outer contours, but not our eyes or mouths (except of course when the shadows are perfect profiles). In order to paint the frescoes, Michelangelo would, of course, need more than the simple outline of the figures. The task of adding features to the projected silhouettes is relatively straight-forward, because the artist can use the outer counters as guides for where the internal features should be. Michelangelo could refer to the clay models directly, or drawings of them, when adding the features to the projected drawing. A red chalk study of the horse (left column) would likewise enable us to fill in the details for a fresco cartoon.

Earlier it seemed necessary to justify why Michelangelo would have made clay models of figures such as Haman. But at this point we could ask a different question. If he had the clay models, why should Michelangelo have made the refined red-chalk drawings of them? The fact that these drawings exist does not in itself explain their purpose. If Michelangelo made clay models, as I described, and if he used them to project the outline of the figures on the ceiling, he could have also referred to the models themselves to add the other details to the projected image. The red-chalk drawings would thus seem to be unnecessary. Thus, in a sense we have come full circle in the argument.

We see now that the refined nature of the red chalk drawings poses a difficulty for the clay model shadow projection idea. If Michelangelo had the clay models, it seems that the refined drawings would be unnecessary. But since the refined red chalk drawings exist, we must show how they would still be essential to the project, along with the proposed clay models. If we cannot do this, then we are forced to assume that Michelangelo made these refined red chalk drawings for no particular reason. Since this would be absurd, it would cast doubt on the clay model idea.

The solution to this dilemma is simple, however. Although Michelangelo could have used clay models to transfer line drawings of his figures to the ceiling (by tracing the shadow, and adding interior contours referring to the model), he still needed to paint the frescoed figures with the appropriate light and shade. Theoretically, he could have painted from the models directly. However, there is a problem in doing this. The lighting in the Chapel by which he worked in painting the frescoes would likely not be the same as the lighting he wanted for his clay figures. Moreover, because the frescoes are large, he would have to move the clay figures around as he changed position, in order to always view them from the correct angle. An easier solution than painting the frescoes directly from clay models would be to make refined shading studies of the clay figures, using the correct lighting, and then to refer to these as he painted. This, I believe, is the purpose of the refined red chalk drawings in the Michelangelo Drawings exhibition, such as that of Adam, Haman, and the Ignudo. Thus, the red chalk drawings still have a fundamental role to play in the making the frescoes, even if Michelangelo made clay figures. A drawing has advantages that a clay model lacks, as a reference for painting: portability, invariance over different lighting conditions, and constant viewing angle of the figure.

Previously it was assumed that the refined red chalk drawings in the Michelangelo Drawings exhibition are an early stage of the project — something from which full-scale, refined cartoons could be made. With my interpretation, the cartoons — that is, full scale drawings to be attached to the ceiling itself to allow the drawing to be transferred to the wet plaster — would need be no more than minimalistic outlines and interior contours. The refined red chalk drawings we see in the exhibition could be a primary source for the fresco painting detail. This is an attractive idea, because it explains why the drawing are executed with such refinement. It is also an exciting idea because it puts the drawings we see much closer to the final result: Michelangelo might have even held these drawings in his hand as he painted. The fact that the drawings are incomplete — missing heads or arms — is of no importance. Michelangelo would have had these pieces on separate sheets, or even on the same sheets, as was his habit. To paint the head from one page, the body from another, would present no inconvenience, given that a complete outline and major interior contours had been transferred from the cartoon to the wet plaster. In fact, dividing the figures into separate parts would make it be easier to use them, because the heads could be made in larger sizes in the drawing to show better detail.

No full-sized fresco cartoons for the Sistine Chapel ceiling have survived. Vasari suggests that Michelangelo burned the cartoons. Perhaps this was not as absurd as it sounds — if the fresco cartoons were indeed as minimalistic as I suggest, and that the best drawing work was confined to the small (red chalk) drawings, some of which still exist and are on display in the exhibition.

Conclusion

We began with a search for traces of Michelangelo’s lost 3-dimensional sketches. We found what could be careful depictions of some of them in the red chalk drawings for the Sistine Chapel ceiling.

During the difficult years of creating the ceiling frescoes, the artist signed his letters to his family with the title, “Michelangelo, Sculptor in Rome.” During this time he was not able to create the marble sculpture that was his passion, and it is easy to regard this title “Sculptor” as more wishful thinking than as directly connected to his activities from 1509 to 1513. And yet, as we have seen in this essay, the designation “Sculptor in Rome” could have been literally true during the fresco project. Michelangelo may have formed clay models of his figures, and used them to transform his ideas onto wet plaster. If we take Michelangelo at his word and consider this possibility, we are able to reinterpret the entire process of creation of the ceiling frescoes of the Sistine Chapel.

Notes

1 A small collection of model figures was found in the Casa Buonarroti in Florence. There is some mystery surrounding their origin. Other figure models elsewhere have been attributed to Michelangelo as well, but authenticity is generally a matter of controversy.

2 Michelangelo also modeled with wax, and perhaps other media. Giorgio Vasari, Michelangelo’s friend and biographer, records that the sculptor carved the colossal marble ‘David’ from a small wax model. Clay is the more plastic and sensuous medium, whereas the wax model is less fragile. Although I refer to clay models in this essay, wax could fulfill the same role.

3 “As with the earlier Cascina figure studies, the fact that Michelangelo was drawing from a model did not prevent him from adjusting the forms for artistic effect.” See Hugo Chapman’s Michelangelo Drawings: Closer to the Master, p. 129

4 The makers of the Michelangelo Drawings exhibition are of course not ignorant of the possibility that Michelangelo could draw from small model figures. But they use this concept to reach an odd conclusion. With reference to the fact that the drawing technique for A flying angel and other studies is crude and mechanical, they suggest that this may be a result of Michelangelo drawing from a small model figure. Given Michelangelo’s talents in sculpture and drawing, this argument is inexplicable; it is as if to suggest that Michelangelo would have found his own sculptural models uninspiring subjects. In another essay I give a different explanation for the quality of the drawing in question, namely, that it may be a forgery.

5 Quoted from Daniel Thompson’s translation, The Craftsman’s Handbook. Cennini believed that life-casting was also the basis of sculpture in ancient times, from which, he says “many good figures and nudes are to be found.” In light of the ancient Roman marbles that would be unearthed after Il Libro dell’Arte was written, Cennini’s statement about “many good figures” is indeed prescient.

6 The only important difference is that the clay models for the Sistine Chapel would require less work, because unlike the case of marble sculpture, the figures in the frescoes can only be seen from a fixed viewpoint, not from any side. Michelangelo would not need to worry about the muscles of Adam’s back, or the chest of the Ignudo depicted from behind. In other words, making the clay models for the Sistine chapel would have been familiar work to Michelangelo, but less demanding than what he was used to in his usual work as a sculptor.

7 Michelangelo was the master of transformation from the real to the ideal. For example, in what is apparently a non-idealized life-study for a figure in the Sistine Chapel ceiling frescoes [a drawing not in the Exhibition], Michelangelo depicted “an elderly man with a slight paunch and sagging buttocks. ” Michelangelo somehow transformed this ordinary man into one of his heroic, gargantuan fresco figures; furthermore, in the chapel, the figure is a woman. [See Michelangelo and the Pope’s Ceiling, by Ross King].

8 Hugo Chapman writes, “There are no known examples of Michelangelo squaring his preparatory drawings so one can only assume that he copied them freehand.” p. 120. This freehand copying and enlarging of the figures would be a huge amount of work, and very difficult because of the curvature of the ceiling. As I explain, there is a much simpler alternative.

9 A model of the Sistine chapel ceiling would have been of great help to Michelangelo, whatever method he used to transfer his drawings to the ceiling.

With the real ceiling, the artist standing on the scaffold sees a highly distorted view of his work; the spectator standing far below on the chapel floor sees the work in the correct perspective (if the scaffold does not block his view).

With a small scale model of the ceiling, the artist can see his work in correct perspective, and also work at the same time.

To enlarge the design from the model ceiling to the full-scale ceiling is trivial. Thus, working with a model ceiling offers an advantage in preparing designs for the ceiling frescoes, because the artist can deal with the problem of the curved ceiling while working, and enlarge the scale later.

Furthermore, if Michelangelo had a small model of the ceiling with which to work, he could position himself in the intended viewing position for the fresco and draw at the same time. Working in the real chapel, Michelangelo could not stand in the intended view-point at the same time he worked. When seen from the intended viewpoint, the figures on the fresco would not seem distorted by the curvature of the wall, by definition. Thus, drawing from this position is easy. However, from other viewpoints, particularly the extremely close viewpoint necessary to paint the actual frescoes, the distortion of the figures would be extreme.

The fact that the Sistine Chapel ceiling consists of a small number of repeating elements means that a small set of simple models of the ceiling would suffice. There would be no need to construct a model of the complete chapel ceiling. The model ceiling segments could have easily been constructed from wood.

Michelangelo was famous for working in secrecy. The technique of shadow projection I discuss is so simple and rapid that, if he used it, he could easily have hidden the technique from his own assistants.
References

Cennini, Cennino. Il Libro dell’Arte. The Craftsman’s Handbook. Trans. Daniel V. Thompson. New Haven: Yale University Press, 1933.

Chapman, Hugo. Michelangelo Drawings: Closer to the Master. London: The British Museum Press, 2005.

King, Ross. The Pope’s Ceiling. New York: Penguin Group, 2003.

Vasari, Giorgio. Lives of the Painters, Sculptors, and Architects. Trans. Gaston du C. de Vere. 2 vols. London: Everyman’s Library, 1996