The Poussin Project
The year in the life of conservation
Welcome to the online conservation treatment diary for Nicolas Poussin’s Crossing of the Red Sea. Over the course of this year-long treatment we will be presenting a series of informal updates designed to keep the public informed about the restoration of one of the NGV’s most prized paintings.
The Crossing of the Red Sea (1632-1634)
oil on canvas
155.6 x 215.3 cm
National Gallery of Victoria, Melbourne
Felton Bequest, 1948
1843-4
Fourteen months in 70 seconds
Witness the transformation of Poussin’s Crossing of the Red Sea in this slideshow chronicling the various stages of conservation treatment: the removal of old varnish and restorations, the application of a new varnish, and the gradual process of inpainting the lost and worn passages of paint. If you look closely you will notice the changes first in the lower half of the painting, then up through the mountains and landscape, and finally throughout the sky.
The mystery figure in the NGV Crossing of the Red Sea
2011-11-07T15:29:00.001+11:00
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| Detail of NGV Crossing of the Red Sea by Nicolas Poussin |
Therefore during the cleaning it came as a surprise to discover that the face was in fact original to the painting. Unlike the other areas of restoration, the paint of the face was not soluble in the cleaning solution, and when examined under high magnification it appeared consistent with the surrounding original paint with a similar craquelure, brush and pigment characteristics. But how could it possibly be by Poussin when the other copies and replicas told us the figure was turned the other way?
- Leave the figure as it currently exists, that is, with the “old” head on the “new” body.
- Leave the “old” head, but paint out the added part of the body so that the older version of the figure appears in its original form.
- Re-paint Poussin’s modified head, covering over the original, thereby returning the figure to the final appearance left by the artist.
The rediscovery of a “lost” replica
2011-10-21T09:00:00.000+11:00
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| Attributed to Charles Le Brun, Crossing of the Red Sea (after Poussin) Oil painting on canvas, 158.1 x 213.4 cm The Iris and B.Gerald Cantor Center for Visual Arts, Stanford University, USA |
Before conservation treatment.
The discovery of the replica has given us much to consider in light of the current restoration but also more generally in regards to Poussin and how we interpret his images.
Using copies to learn about lost information
2011-10-10T13:55:00.004+11:00
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| Engraving by Etienne Gantrel |
Removal of varnish and old retouchings
2011-08-01T10:52:00.000+10:00
Cleaning tests had revealed that the old varnish - applied by Horace Buttery in 1960 - could be removed using standard cleaning solutions without risking Poussin's paint surface. So what do we mean by a standard cleaning solution?
Well, first it depends on the type of varnish being removed and the vulnerability of the underlying paint. Critical to the ability to safely remove varnish from most paintings is the condition that oil paint is different to varnish resin in terms of chemical structure. We can exploit this difference by selecting solvents which affect the resin without breaking down the structure of the oil.
For many Old Master oil paintings covered with a traditional varnish such as dammar, paintings conservators will frequently use a blend of an "active" solvent, such as acetone or possibly isopropanol, with a "diluent" solvent such as mineral spirits. The diluent solvent has the effect of controlling the solubilizing of the varnish by the active solvent; essentially, it slows down the rate of removal, allowing the conservator to work in a measured way.
If the paint layer underneath the varnish proves to be highly vulnerable with these types of organic solvents there are other cleaning systems available to the conservator. However, the vast majority of pre-1800 paintings are cleaned with solvent mixtures. For the Crossing , a solution of one part acetone to one part mineral spirits was used for the first pass of cleaning, in which the bulk of the varnish was removed. For the second pass, the amount of acetone was reduced, and for the third stage of scalpel removal of old restorer's retouchings, only mineral spirits were used to help wipe away the debris.
The three main stages of cleaning were completed in about a month. This proved to be relatively straightforward as there weren't many layers of older varnish and retouchings to remove. Clearly, Buttery had cleaned the painting thoroughly in 1960. Poussin's thin and smoothly applied paint surface also aided a quicker varnish removal; where artists have applied paint in thick and textured brushstrokes there is a greater likelihood that old varnish will become lodged in the recesses of the textured paint, and over time these old residues can discolour and become harder to remove.
The visual impact of the varnish removal was appreciable, but not dramatic. Certainly not as stark as this recent cleaning of a sixty-year-old varnish we undertook from Giambattista Tiepolo's & nbsp Finding of Moses :
With the Poussin, the most visually striking thing about the cleaning was not the removal of the varnish but of the old retouchings. As we had anticipated, the dark clouds on the right side of the painting were worn right down to the priming layer:
Above is the painting before treatment
Here is the painting after removal of the varnish and old retouchings.
In addition to these we also noted the full extent of another type of old damage to many of the areas of flesh-coloured paint. Several of Poussin's thinly applied skin tones displayed numerous small pit-like losses, leaving the surface looking broken and with less definition:
The enlarged detail above shows just how many of these losses there are in the surface, creating a visual chatter which makes it hard for the eye to read Poussin's original brushwork.
With the varnish removed the full extent of the work which lies ahead has been revealed . The painting needs to be revarnished, and then inpainted in the areas which have suffered the most damage. In areas such as the clouds, a considerable amount of inpainting will be required to mask the damage and reconcile them with the best preserved passages, so that the painting displays a consistent level of surface condition.
Crossing the Red Sea - literally!
2011-05-11T09:56:00.024+10:00
Previous restorations
2011-04-19T16:55:00.003+10:00
The revelations of UV photography
2011-03-16T15:01:00.004+11:00
As we draw closer to the cleaning of the Crossing of the Red Sea we turn our attention to UV photography. A quick glance at an image of the painting under ultraviolet light is enough for a conservator to learn some of the critical issues regarding its surface, especially the condition of the old varnish and the previous restorer's work.
However, what is more notable about this photo are the very dark patches which interrupt this overall pale effect. They are indicated with the arrows in the photo below:

These dark areas are patches of retouching applied by Horace Buttery - the previous restorer - in 1960. The extent of dark areas of the clouds and trees tell us that he needed to do quite a lot of work in those areas, suggesting that the underlying original paint was damaged or worn some time earlier.
When we look at a detail from the UV photograph we can see that there are also considerable smaller retouchings in the sky which are not visible under normal light:

These old damages and repair are not uncommon in canvas paintings as old as the Crossing of the Red Sea , so are not cause for alarm. What they mean in terms of the treatment ahead is that the cleaned painting will reveal the wear and tear the painting has endured, and that the upper part of the painting will require more work to reintegrate than the lower part containing the figures, which is in a better state of preservation.
A strategy for cleaning, Part 2
2011-02-23T15:57:00.003+11:00
First stage of varnish removal
If the solubility tests suggest the cleaning will not present any particular problem, the first part will involve a first broad cleaning across the painting. The aim of this step is to remove the bulk of the discoloured varnish and restorer's retouchings, leaving fine residues and hard-to-remove retouchings for a later secondary cleaning. Doing it this way gives you an opportunity to assess the cleaning in a gradual and considered way and allows for adjustments to be made you go along. For example the conservator can vary the proportions of the solvents used as it the varnish thins down.
Second pass of varnish and overpaint removal
The second pass allows the painting to be cleaned to a more refined level of consistency across the surface and allows for any problematic areas to be cleaned on their own terms. Quite often older restorer's retouchings were painted in oil, making them more difficult to remove. Removing them during a second stage of cleaning enables them to be treated locally.
Mechanical removal
Sometimes old retouching paint and varnish is resistant to solvent cleaning. When this occurs, they may need to be cleaned mechanically. This is often done manually with the aid of a scalpel, delicately scraping or chipping the non-original components away from the original. This is almost always done under magnification, either with a magnifying loup or else under a stereomicroscope. It can be very time-consuming.
Final Balance
The later stages of cleaning are about ensuring that the painting has been cleaned to a consistent level of finish. Throughout the process the conservator ought to have developed a clear idea of what he or she wants to achieve with the cleaning and what is the best that can be reached given the variables involved: the condition of the original paint layers; how vulnerable they may be to the cleaning solution, the feasibility of removing the varnish and overpaints, the aesthetic implications of removing the non-original components, and so on.
Ideally the final balancing stage of cleaning provides the opportunity for final subtle adjustments to be made to reach the appearance required.
A strategy for cleaning Part 1 - testing
2011-02-16T09:47:00.003+11:00
Tests under magnification
The first stage will involve testing of the solubility of the varnish and potentially the paint films. During an examination it usually clear what type of varnish lies on the surface and what type of paint medium has been used by the artist. With that knowledge a suitable varnish removal solution is selected and tried out on a tiny area of the surface of the painting, usually near an edge.
This is generally done with the aid of a magnifier or microscope to see how the varnish and paint respond to the cleaning solution. If problems occur the choice is clear: stop or otherwise find another an alternative cleaning mixture, or perhaps a different method of cleaning. In most cases, when the varnish and paint layers are properly understood it does not take long to arrive at a suitable method.
Small windows on different areas of the painting
Once the cleaning tests indicate that the old varnish can be safely removed, the next stage in the process will involve carrying out slightly larger tests in different passages of the painting. The aim of this part of the process is to determine how the cleaning solution works in different parts of the painting.
The surfaces of paintings are not uniform in their composition; certain traditional pigments - for instance lead white - often form stronger and more resistant paint films than others, such as vermilion red or azurite blue. Other colours might be more vulnerable because the artist may have added a resin (similar to the varnish medium) to the oil paint medium, making it potentially vulnerable.
Furthermore, some parts of the painting might contain a different paint medium altogether: In the seventeenth century it was customary for some painters to use a medium other than the usual linseed oil for specific pigments. It was not uncommon for blues to be painted with walnut or poppy oils, which were less prone to yellowing than linseed. Other painters used a glue-like medium for blues. Investigations into Poussin's materials have shown that he generally used linseed oil but did employ walnut oil for some blues and occasionally added pine resin to his paint.
For this reason, all potentially vulnerable areas of paint need to be tested. Once this has been done it will be time to commence the removal of old varnish and restorer's overpaints.
X-raying the Poussin
2011-01-25T14:26:00.001+11:00

This is what a single plate looks like once it is processed. To get the most value out of the technique it is usually preferable to join all the other plates together so that the image for the whole painting can be read in one go. In the past this used to be done on large light boxes, but it is now done with digital imaging technology. To do that, each plate is digitally scanned. The scanned images are then assembled on a computer, using imaging software to form a large composite image.

The above image is the digitally assembled radiograph for the painting. It reveals not just the painting on the canvas but also the wood stretcher and all the other components which hold the work together. Radiographs can be very useful for determining the condition of those structural components, particularly for paintings on wood panels. However, there are other times when the image of the stretcher can impede our examination of the painted surface. In these cases we are able to digitally adjust the radiographic image to reduce the effect of the stretcher, as we see in the image below.

Now we are able to recognize the image of the painting and can make some assessment about the artist's technique. The fact that the radiograph corresponds with the painting as we normally view it tells us that Poussin did not make wholesale changes to the painting while he was at work.
We saw in the earlier post about Poussin's modifications that some of the smaller changes - such as adding clothing to naked figures - were visible in close up details of the radiograph, but on the whole no large scale alterations are present.
On some paintings radiographs will reveal radical changes or even an earlier painting underneath the final image. Here is an example: In this detail of a painting by the eighteenth-century painter Joseph Wright of Derby you can see another face. This is from a much older portrait which sits beneath Wright's.


We will return to the Poussin radiograph throughout the year as questions about different parts of it come into focus, whether they concern the materials or technique or damage.
In the next post we will look at the painting under ultraviolet light.
Exodus 14
2011-01-24T14:59:00.003+11:00

Moses stretching his hand out over the sea to close the water over Pharoah's men. The "pillar of fire" is at the right edge of the painting.
Exodus 14 is the source text for Poussin's Crossing of the Red Sea . This highly cinematic passage of the Old Testament provides a wealth of details and scenes for narrative painters to draw on, and it is clear that Poussin studied it closely when he began devising his version.
Though Poussin also chose to use this same part of the story, he referred closely to the text for guidance on how to describe the scene. In the painting you can see Poussin has taken note of Moses' carrying a staff (16) and holding his arm outstretched (27). The painter also included the "pillar of fire" (24), and drowned Egyptians upon the shore (30). The "pillar of fire" is a detail which is not not commonly found in many previous interpretations of the story by painters such as Bronzino, Mazzolino and Cosimo Rosselli.
Here is the text:
Exodus 14
1 Then the LORD said to Moses, 2 “Tell the Israelites to turn back and encamp near Pi Hahiroth, between Migdol and the sea. They are to encamp by the sea, directly opposite Baal Zephon. 3 Pharaoh will think, ‘The Israelites are wandering around the land in confusion, hemmed in by the desert.’ 4 And I will harden Pharaoh’s heart, and he will pursue them. But I will gain glory for myself through Pharaoh and all his army, and the Egyptians will know that I am the LORD.” So the Israelites did this.
5 When the king of Egypt was told that the people had fled, Pharaoh and his officials changed their minds about them and said, “What have we done? We have let the Israelites go and have lost their services!” 6 So he had his chariot made ready and took his army with him. 7 He took six hundred of the best chariots, along with all the other chariots of Egypt, with officers over all of them. 8 The LORD hardened the heart of Pharaoh king of Egypt, so that he pursued the Israelites, who were marching out boldly. 9 The Egyptians—all Pharaoh’s horses and chariots, horsemen and troops—pursued the Israelites and overtook them as they camped by the sea near Pi Hahiroth, opposite Baal Zephon.
10 As Pharaoh approached, the Israelites looked up, and there were the Egyptians, marching after them. They were terrified and cried out to the LORD. 11 They said to Moses, “Was it because there were no graves in Egypt that you brought us to the desert to die? What have you done to us by bringing us out of Egypt? 12 Didn’t we say to you in Egypt, ‘Leave us alone; let us serve the Egyptians’? It would have been better for us to serve the Egyptians than to die in the desert!”
13 Moses answered the people, “Do not be afraid. Stand firm and you will see the deliverance the LORD will bring you today. The Egyptians you see today you will never see again. 14 The LORD will fight for you; you need only to be still.”
15 Then the LORD said to Moses, “Why are you crying out to me? Tell the Israelites to move on. 16 Raise your staff and stretch out your hand over the sea to divide the water so that the Israelites can go through the sea on dry ground. 17 I will harden the hearts of the Egyptians so that they will go in after them. And I will gain glory through Pharaoh and all his army, through his chariots and his horsemen. 18 The Egyptians will know that I am the LORD when I gain glory through Pharaoh, his chariots and his horsemen.”
19 Then the angel of God, who had been traveling in front of Israel’s army, withdrew and went behind them. The pillar of cloud also moved from in front and stood behind them, 20 coming between the armies of Egypt and Israel. Throughout the night the cloud brought darkness to the one side and light to the other side; so neither went near the other all night long.
21 Then Moses stretched out his hand over the sea, and all that night the LORD drove the sea back with a strong east wind and turned it into dry land. The waters were divided, 22 and the Israelites went through the sea on dry ground, with a wall of water on their right and on their left.
23 The Egyptians pursued them, and all Pharaoh’s horses and chariots and horsemen followed them into the sea. 24 During the last watch of the night the LORD looked down from the pillar of fire and cloud at the Egyptian army and threw it into confusion. 25 He jammed the wheels of their chariots so that they had difficulty driving. And the Egyptians said, “Let’s get away from the Israelites! The LORD is fighting for them against Egypt.”
26 Then the LORD said to Moses, “Stretch out your hand over the sea so that the waters may flow back over the Egyptians and their chariots and horsemen.” 27 Moses stretched out his hand over the sea, and at daybreak the sea went back to its place. The Egyptians were fleeing toward it, and the LORD swept them into the sea. 28 The water flowed back and covered the chariots and horsemen—the entire army of Pharaoh that had followed the Israelites into the sea. Not one of them survived.
29 But the Israelites went through the sea on dry ground, with a wall of water on their right and on their left. 30 That day the LORD saved Israel from the hands of the Egyptians, and Israel saw the Egyptians lying dead on the shore. 31 And when the Israelites saw the mighty hand of the LORD displayed against the Egyptians, the people feared the LORD and put their trust in him and in Moses his servant.
THE HOLY BIBLE, NEW INTERNATIONAL VERSION®, NIV® Copyright © 1973, 1978, 1984, 2010 by Biblica, Inc.™ Used by permission. All rights reserved worldwide.
Some changes in the painting
2011-01-18T16:16:00.002+11:00
We can be sure the Crossing of the Red Sea does not look the way it once did. All paintings are affected by the passage of time, in both structure and appearance. There is one aspect of change in Poussin’s work which has been frequently commented on: a shift in the painting’s tonal values. By this we mean that the visual balance between the light and dark tones seems to have changed over the centuries. The belief is that many of Poussin’s paintings are darker in appearance than they once were as a result of the increasing transparency of some of his pale pigments and the artist’s technique, with his paint applied in rather thin layers.
It is quite possible that the water washing against the shore in the lower right of the painting is less prominent than it once was, and that the earth colours of the foreground shore area are also darker than originally intended. Several pigments are known to change appearance over time: some blues can turn black, others turn grey, some greens can change to brown. The blues in the Crossing of the Red Sea appear much darker than the same blues seen in a seventeenth-century replica of the painting, but for the moment we cannot quantify this change. Scientific analysis later in the year may help give us some indication about how much change has taken place.
Knowing about these types of changes can help us get a more informed understanding about Poussin's intentions and can perhaps steer us away from any misconceptions which might otherwise arise.
Changes in the painting's structure
There are other changes in the painting which are not apparent to the general viewer.
This photograph shows the reverse of the Crossing of the Red Sea. No visible part of it is original to the painting. The wood stretcher which holds the canvas probably dates from the second half of the nineteenth century. Stretchers are replaced when the previous one is damaged or inadequate to support the weight and shape of the picture. It is quite possible that the stretcher it replaced was also not Poussin’s original.The canvas visible on the reverse also probably dates from the nineteenth century. This is a lining canvas, which was bonded to the back of the original to give it greater strength and the rigidity needed to prevent the paint and priming layers from breaking up.
The thin horizontal strip of canvas in the upper part of the reverse is an additional piece of canvas added to provide further rigidity over the seam of a join in the original canvas. Possin's original canvas is made up of two pieces of canvas sewn together - as we will see in a later x-radiograph. With time and movement, the join line has caused a horizontal crack line visible from the front of the painting, so the strip was applied over the reverse of the lining to prevent further weakening of this vulnerable area.
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| A detail of the top left edge of the painting. |
The photo above shows how the original unpainted edges of the canvas have been trimmed, so that the painting is held onto the stretcher only by the lining canvas. We always check this feature during the examination to determine whether the painting has been cut down. If the original edges are intact, then we can say that the painting retains its original proportions. Sadly, it is not uncommon to find paintings which have been cropped into a smaller size. Though the edges of the Poussin have lost their original unpainted edges, we know by other means that there has been no cropping of the painted surface.
In the next post we will look at how the painting was x-rayed.
Pentimenti
2011-01-14T10:14:00.000+11:00
A pentimento in the landscape
Poussin’s preparatory technique was famously rigorous and highly planned, yet he too frequently made adjustments as he went along. The Crossing of the Red Sea is full of changes to both the landscape and the figures.

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The dark areas of the radiograph are not caused by dark paint, but rather by the absence of the x-ray-absorbent paler pigments which were used for the sky. When laying in the paint of the sky Poussin painted around the area he intended for the mountain, and the area he left unpainted was the space he left for his intended mountain. The radiograph suggests that when he painted the left peak he had to paint over an area originally intended to be sky.
Pentimenti in the figures
Another type of pentimento common to Poussin is the addition of draperies to figures he first painted nude. The three primary figures of the painting were all painted nude and were “clothed” after the figures were complete. This was not done out of prudery but as part of his process to create harmony of groups of figures by arranging them first in their most elemental form, unencumbered by heavy clothing . In the following images you can see a detail of the central figure and its corresponding radiograph.


The naked form of the figure is clearly visible in the radiograph, with the streaky brushstrokes of the upper leg and hip visible beneath the almost horizontal brushstrokes of the blue drapery.
Finally, there are plenty of smaller pentimenti scattered throughout the picture which are visible to the naked eye, such as in the headscarf of this female figure below. For some reason Poussin decided to extend it down further than he originally painted it, so he was obliged to cover part of the head of a background figure, with the ear of the male figure visible beneath.

In the next post I will show you some of the changes to the painting that have been brought about by the passage of time
Getting started
2011-01-11T10:11:00.000+11:00

No conservation treatment ever begins by getting straight into the physical act of cleaning or repairing the picture. It is always preceded by a phase of looking, learning and recording. These simple-sounding steps are some of the most important things a restorer needs to do to ensure a successful outcome to a treatment. They are also continuous from the beginning to the end of the job.
The amount of time needed before treatment can begin will depend on the amount of information available about the work and complexity of the problems the painting presents.
Paintings are objects created expressly for looking and contemplating. Understanding the painting as an image left to us by the artist is the first part of the conservator's duty. Equally important is the need to assess the painting as a physical object on its journey through history. Time can cause permanent changes to the look and structure of a painting, so it is therefore essential for the conservator to be aware of these changes. A thorough examination enables the whole process to take place from a foundation of knowledge and sensitivity to the requirements of the painting.
The work needs to be observed from all vantage points: up close, from a distance, and under different lighting conditions; with the naked eye, the magnifier and the microscope. There is also much to be learnt from examining the sides and the reverse of the picture. A lot of hidden information is contained there which can reveal its history.
Learning
The learning takes place with the aid of examination, surveying the relevant historical literature, conservation research and records and online sources. Discussions with curators, conservators, scientists and art historians are also important in understanding the breadth of issues surrounding the painting.
Recording
The recording is done with documentation, photography, scientific analysis, radiography, infrared reflectography and any number of analytical tools available to the conservator. All of this material is compiled and retained in the department’s records for reference, and is eventually fed into the wider body of conservation research.
When a painting is as old and significant as the Crossing of the Red Sea, there will inevitably be extra information to absorb. Over the past few months we have been able to bring the picture to the NGV conservation studio to familiarise ourselves with it and the literature surrounding it.
Like many regular visitors to the Gallery I looked at the painting for decades in awe of its imposing grandeur and its flow of bodies and colour, but I have also been able to observe it for a long time from the conservator’s critical perspective. It is one of the privileges (and perhaps one of the curses) of conservators that they are able to see in an artwork not just what history has left to us, but also what it has taken away. With Poussin generally, and with Crossing of the Red Sea in particular, it is critical to know that the painting in its present state does not appear as it did in the seventeenth century. There have been considerable changes to the picture, some of which are irreversible.
In the next few posts we will look more closely at some of these things we have learned about the painting.
An introduction to the project
2011-01-04T10:08:00.004+11:00

Welcome to the online conservation treatment diary for Nicolas Poussin’s Crossing of the Red Sea . This is the first instalment of a series of informal updates designed to keep the public informed about the restoration of one of the NGV’s most prized paintings.
The main aim of this diary is to provide you with the opportunity to look in on the many steps required to bring such a treatment to completion. Large scale conservation treatments can take months, sometimes even years. They require patience, discipline and planning. We hope the real-time release of news about this treatment while it is in progress will enable you to experience something of the journey the painting and the conservator take as the treatment unfolds.
What does the term “conservation treatment” mean? Broadly speaking, the treatment of paintings falls into two main categories: structural and superficial. Structural work involves the repair of components of the picture which can no longer properly serve their physical function, such as a canvas that is torn, a panel which is split, or paint layer which is flaking.
Superficial treatment concerns work to the surface of the painting, for example the removal of old varnish and restorer’s overpaints, the application of a new varnish, and the retouching of lost or worn areas of paint. Both structural and superficial treatments are time-consuming and demand a ongoing process of adjustment and decision-making to reach the best balance between the demands of the artwork and its material condition. The Poussin treatment will mainly involve surface work.
Any canvas painting as old as the Crossing of the Red Sea - which we know was painted around 1634 - is bound to have its share of conservation issues. Few paintings emerge unscathed even after a century. For that reason, and also on account of its size, a full year has been set aside to complete the restoration and return the painting to the Gallery walls.
This is the first time we have undertaken an informal online record of a major treatment like this, so it will undoubtedly take time for us to exploit this medium, but we shall try at the very least to accompany the written posts with photos and where possible, with audio-visual content.
We hope you enjoy the process!



































