JAIC 1977, Volume 17, Number 1, Article 1 (pp. 01 to 08)
JAIC online
Journal of the American Institute for Conservation
JAIC 1977, Volume 17, Number 1, Article 1 (pp. 01 to 08)

HELMUT RUHEMANN'S INPAINTING TECHNIQUES

Bettina Jessell

ABSTRACT—Ruhemann's philosophy of inpainting is discussed, including his belief in the role of the conservator as connoisseur. Materials for filling losses, inpainting and varnishing tempera and oil paintings are given, along with methods of their application. The author lists pigments she finds useful to achieve specific effects, and demonstrates that it is essential for the conservator to imitate the methods of the artist in order to inpaint successfully.


1 INTRODUCTION

It is difficult to know to what extent I carry on Helmut Ruhemann's inpainting techniques faithfully, or to what extent I have devised methods which suit me and use newly developed materials. However, my thinking is still closely based on Ruhemann's teaching and philosophy, and I hope and am persuaded that nothing I do would meet with his disapproval. Of course new materials often simplify methods, but they do not really affect the fundamental principles.


2 CHOICE OF TECHNIQUE OF INPAINTING

On this question Helmut Ruhemann was not dogmatic, and I agree with him that the exact technique used should suit the individual painting and the school of painting from which it derives. In some cases his inpainting was limited to underpaint and monchrome undermodelling only; in other cases he added matched inpaintings in some passages of the painting, as in the Nativity by Piero della Francesca in the National Gallery in London. I have on occasion used undermodelling and no other inpainting on works where scholarship rather than artistic consideration was important, as shown in Plate 1. See Section 16.

This method of using undermodelling only is suitable for early and much damaged paintings, which are really drawings colored in. By contrast, the whole point of a Baroque painting is the way in which the eye of the beholder sweeps through the movement of the composition at the painter's bidding, and this is ruined if the eye meets the obstacles of unmatched inpainting.

In Helmut Ruhemann's opinion the ethical objections to completely matched inpainting lost much of their force with the introduction of the use of ultraviolet light to reveal new paint. So as not to deceive the public, I would like to see museums display next to every painting a small photograph of the painting after cleaning and before inpainting.

As a rule, Helmut Ruhemann used matched inpainting, which he carried to virtual perfection.


3 CONNOISSEURSHIP FUNDAMENTAL TO SUCCESSFUL INPAINTING

One of Helmut Ruhemann's great contributions to the art of inpainting was his insistence on following the methods of the original painter exactly, and on understanding the painter's artistic intention. That can only be done by a restorer who has a thorough knowledge not only of the technique of a particular painter, but also of the visual experience which the painter is trying to communicate by means of this technique; in other words, connoisseurship. This to Helmut Ruhemann was the most important attribute a restorer can possibly have, and one which he spent a lifetime teaching and passing on to his pupils. Just before his death he said to me sadly that connoisseurship was declining and that he feared it would die out. I feel that was the pessimism of age. As long as there are great paintings there will be many people who will steep themselves in these paintings, and so, as it were, get on the same wave length as the painter. It is that, together with knowledge of technique, which makes connoisseurship.


4 QUALITY

Connoisseurship helps in judging quality. Quality is a concept difficult to formulate, though among people in constant contact with good paintings there does seem to be general agreement as to where it is present and where it is absent. In addition to all the obvious requirements for quality such as good drawing, harmonious colors, satisfying composition, it has to do with a sensitive feeling for the rhythm of contrasting warm and cool tones, and with a feeling for the way light interacts with form and space. A great painter adds a creative and original vision.

It is the job of the restorer to bring back, as far as possible, the quality of the painting. This will to some extent have been irretrievably lost by damage due to age, but will usually, to a much greater extent, have been temporarily obscured by layers of darkened varnish and grime and old disfiguring overpaint. It has to be brought back by conscientious cleaning and by skilled inpainting. Quite a small area of clumsy inpainting can degrade a whole painting.


5 INPAINTING IN LAYERS TO PRESERVE QUALITY

There are three attributes essential to quality which have to be imitated by the restorer, and they are all achieved by building up inpainting in layers. They are:

  1. Luminosity, the phenomenon which makes some surfaces reflect light in such a way that they appear to be lit from within. The most striking example of this is human skin. Painters of all ages have struggled to imitate it in paint, and older painters often succeeded by using a brilliantly light ground under a layer of complete undermodelling, with final color glazes.
  2. Cool transitions, which the older painters usually achieved by applying a translucent light paint over dark paint, make the light paint appear much cooler than it really is. This is called the ‘turbid medium effect.’ A thin layer of the warm medium tone would be applied over the edges of the warm shadow, and so automatically provide the cool transitions which enhance quality, as shown in Plate 2.
  3. Texture, which is characteristic of each painting, depends on the way the brushstrokes are applied and the viscosity of each paint layer.

It follows that to preserve the quality of the painting, the restorer has to build up his inpainting in the same layers as the painter used, ground, underpaint and design layer, and imitate the original paint not only in color but also in texture and luminosity as closely as possible.

As a matter of fact, though this seems like a cumbersome process, it actually saves time, because it makes invisible inpainting so much easier to achieve. Color matching ceases to be a problem because one design layer color applied thinly or thickly over the correct underlayers will match the original paint over a surprisingly large area. This is a consequence of the fact that the painter got his color variations in just that way.


6 FILLING

Filling is boring and difficult, but it is essential to get it right for the success of invisible inpainting.

After many years of experimenting I still come back to Helmut Ruhemann's putty as the best filler. It has a smooth texture, clings well, does not shrink or expand, and can be easily removed.

The following is a satisfactory formula:-

  • 60 grams gilders whiting
  • 15 grams stand oil
  • 20 grams animal glue in water, rather viscous
  • 10 grams zinc white
  • 5 grams bees wax

Combine all ingredients on a hotplate warm enough to melt the wax, and knead together to a smooth consistency.

Before filling a damage it is advisable to varnish the painting to prevent hair cracks from inadvertently filling with putty. Apply the putty to the hole with a small spatula, then use a small flat piece of balsa wood to push it home. Moisten the balsa wood slightly, and with circular motions wipe the surface of the filler flat and flush with the paint surface. In this way the putty fills the hole and finds the right surface more or less automatically. Where necessary, imprint canvas grain at this stage with a matching canvas grainer made of a thin layer of a resin which sets hard without losing all flexibility on fiberglass cloth.

Allow the putty to dry, and then scrape with a scalpel until the edges of the damage appear sharp and the surface is smooth. The surface should be slightly lower than that of the surrounding paint to allow for the thickness of the inpainting.

Insulate the surface of the filling with a thin coat of shellac, taking the greatest care not to go beyond the edges of the damage. Finally, where there is putty over the original paint, wipe it off with mineral spirit.


7 INPAINTING MEDIA

The inpainting medium should look and behave like the original medium, but must not darken with age.

For tempera paintings I still like to use egg tempera, yoke and white, with a little additive of wax for elasticity and a wetting agent like ox gall. Some very smoothly painted tempera surfaces are better imitated in egg white and wetting agent leaving out the yoke and wax. The great disadvantage of tempera as a medium is that it darkens considerably in varnishing, some pigments more than others, so that its use needs a great deal of experience. The paint has to be applied, dried with a hair drier, burnished with an agate, and tested with a little mineral spirits to see whether it will match the original color when varnished.

For inpainting oil paintings, I find that Paraloid B72 imitates the translucency of the original paint better than any other medium I know. As the technique and the quality of an oil painting depends largely on the fact that oil paint is translucent, it is important not to inpaint in a more covering medium than oil in the design layer. For the ground color a covering medium like resin MS2A is useful.

Egg tempera and Paraloid B72 are the most successful media for imitating the painter's brushstrokes. I use watercolor for the very fine, sharp raised brushstrokes in areas such as the hair or the blades of grass in early paintings. But it must be remembered that watercolor also darkens when varnished.


8 PIGMENTS

Pigments have to be permanent and compatible with each other, and with the medium used.

There are many such permissible pigments, but on the whole I prefer a fairly simple palette, as far as possible using earth colors with translucent additives. It is usually possible to restrict one's palette for any particular painting to very few pigments, often only four or five in addition to black and white, in the same way as the printer probably did.

The sharpness and bite of old oil paint can often be imitated only by adding traces of very transparent pigments such as Indian Yellow, Alizarin Orange, Alizarin Crimson and Bone Black. Although not absolutely permanent, it is permissible to use them in the small quantities needed.


9 COLOR MATCHING IN OIL PAINTINGS

In choosing pigments to match a given color the overriding consideration is the degree of transparency required in each layer, covering for the ground, more translucent for the underpaint and design.

One should further keep in mind that old oil paint consists of two components: the oil medium which has to some degree gone brown through oxidation, and the pigments. Therefore, as a first step I base all colors (even black and white) on a mixture of red and green, covering or transparent according to the layer being inpainted. Then I add whichever pigments seem to match those of the painter's, again transparent or covering as required.

Here is a list of color matching tricks which I have found frequently useful: For a deep inky black

Ivory Black with a little Prussian Blue.

Skin tones

Medium tones

Light Red, (or Cadmium Red or Burnt Sienna) Viridian, Naples Yellow and Titanium White.

Shadows

Add Ultramarine to medium tone.

Skies

Viridian (not blue), Burnt Sienna and Titanium White.

White garments, (shirts, ruffs, etc.)

Titanium White, Viridian, Burnt Sienna, and often some Ivory Black.

Very dark hot glaze

Bone Black and Alizarin Orange

Fiery red glazes on early Italian and Northern painting

Alizarin crimson, Alizarin Orange and Bone Black.

Hot glazes, substitute for Alizarin Orange

Indian Yellow and Burnt Sienna.

Brilliant, light colors

First underpaint in pure White, then glaze with transparent color.


10 INPAINTING A DAMAGE IN AN OIL PAINTING

First establish the structure of the layers by visual inspection of the paint edges, the worn areas where the layers may show through, and the edges of damage.

After lining and placing any fabric inlays, fill with an appropriate putty and press in matching canvas grain. Then apply the ground color in a covering medium and covering pigments. Next apply the underpaint and possible undermodelling in a transparent medium and more transparent pigments, so that all layers will contribute to the final effect, as shown in Plate 3.

For very small losses, I may leave out the ground color and apply the underpaint and design colors only.


11 INPAINTING A DAMAGE IN AN EARLY TEMPERA PAINTING

Again the structure is first established. Then the panel is repaired, and the damage filled with gesso, which must be filed flat with cuttlefish bone and burnished with an agate.

All inpainting is done in egg tempera. First the drawing which must match the original in color and character. If there is any gilding necessary, the red bolus is now applied and burnished, then the gold leaf is applied and burnished and stamped.

The underpaint is applied in a flat wash, terre verte under the skin tones, and often a light yellow under the garments. Skies are rarely underpainted because the painter relies on the brilliant white of the gesso for luminosity.

The undermodelling is then applied in single fine open strokes, allowing some of the green underpaint to show through to provide the cool transitions. (As tempera is a very covering medium, the turbid medium effect cannot operate to make cool transitions).

Finally the colors are glazed on, as shown on Plate 4.


12 TYPES OF DAMAGE IN AN OIL PAINTING

Oil paint is subject to many kinds of damage which need to be inpainted. The following is a list of those found frequently with suggestions on how to deal with them, as shown on Plate 5.

Wear and apparent wear:

This is due to the original paint having been abraded or become more translucent with time.

In canvas paintings wear results in innumerable dots of underpaint or even ground color showing wherever a thread of canvas over-lies another. I know of no other way to deal with this except to inpaint each dot individually, usually in a translucent medium for a reasonably luminous final effect.

Wear in panels usually reveals dark short streaks of woodgrain, especially in thinly painted areas such as the skies of Netherlandish 17th century landscapes. It is difficult to paint out the streaks without making the sky look heavy. The most successful method I know of is to use a very light first layer which is then glazed down to the sky color.


12.1 Cracking

This is due to shrinkage of the paint layer. The wide, bitumen type may have to be treated like a damage. If necessary, the underpaint may have to be inpainted in a covering medium, and the crack in the design layer in Paraloid B72.

Fine cracking should be accepted as part of the nature of the painting. If it is too obtrusive it can be made less disturbing by tactfully interrupting the worst cracks with a few fine short lines of inpaint. Similarly some intersections of two or more cracks can be just touched with inpaint, on the theory that the pattern of cracks is densest there.


12.2 Missing Glazes

If glazes are missing they are likely to have been very thin and can be replaced with transparent pigments in a transparent medium.


12.3 Missing Highlights

Missing highlights can be scumbled in using the most viscous, driest possible Paraloid B-7 rubbed on with the heel of the paint brush. An area of stained original paint can be treate in the same way without making it look overpainted.


12.4 Alien Color

Patches of alien color, such as traces of old overpaint which cannot be removed safely, o fly-specks, or small stains, should be given a covering coat of underpaint, and then glazed with the design layer color in a transparent medium, as shown on Plate 6.


13 HOW INPAINTING AFFECTS QUALITY

The following is an attempt to put into words how Helmut Ruhemann achieved the subtlety which made him a master of inpainting, and which he tried to communicate to his pupils. He taught that not only must the restorer have much knowledge of the methods and devices used by the painter to achieve his effects, but that the restorer must during the whole of the inpainting process be intently conscious of the painter's artistic intention, and alert to his sensitivity, in order not to lower the quality of the painting.

To be capable of that, it is necessary to do a good deal of research on every painting, and to look at as many other paintings by the same painter and of the same school as possible or at least at reproductions. It is therefore highly desirable to have access to a photographic library, or failing that, the restorer can build up such a library by indexing periodicals and books in his or her possession.

All inpainting is a process of selection, and one never can or should repair every minutest damage. It follows that the restorer has to choose which losses have to be most conscientiously dealt with to bring back the orderliness and quality of the painting.

The following are some examples of painters' devices which are found frequently in the works of the old masters. They are based on a sensitive observation of nature, and the restorer must keep them in mind while inpainting in order to convey the painter's intention which is lost because of damage or wear or unsuitable old overpaint.


13.1 Landscapes

To give a feeling of depth, the painting tends to have a dark foreground, a colorful middle ground, and a light cool distance. If there are losses interrupting this structure, as for example, some in a distant plane but near the outline of an object in a near plane, they must be most meticulously inpainted. Dark dots in a passage of sky near the outline of a tree rooted in the fore or middleground will prevent the tree from looking near and the sky from looking far away, and thus ruin the impression of distance so important in a landscape.

Skies are thinly painted for luminosity, and in horizontal brushstrokes for distance. Losses in skies are most disturbing because they interfere with the feeling of distance.

Skies shade from darker on top to lighter towards the horizon, and the horizon is the lightest part of the painting, unless obscured by clouds.

Clouds are 3-dimensional forms, bright towards the source of light, shadowed on the other side.

Distant objects are hazier than near ones.


13.2 Seascapes

Seascapes are mainly structured like landscapes: dark foreground, colorful middleground, cool light distance.

Near objects have sharp reflections in the water, distant reflections are more hazy. In still water, reflections exactly follow the shape of the object.

Missing rigging of ships in the foreground make them look hazy and therefore distant, and must be replaced.


13.3 The Human Figure

Painters of quality observe a rhythm of contrasting warm and cool tones in skin tones. Shadows and middle tones are warm, transitions and highlights are cool.

There is a light reflection under the chin and often along the edge of the shadowed cheek.

When painting the hair, a simple form with light and shade takes precedence over accidental single strands.

All outlines are a little hazy, especially the pupils and irises of the eyes, to avoid a staring look.


13.4 Still-Lifes

All losses in the background must be meticulously inpainted, to allow the background to recede and the objects to come forward.

Hard, inanimate objects are given sharper outline and sharper highlights than living things. Cloth is always a little fuzzy, to avoid having it look metallic.

As a general rule, there can be no highlight without an equivalent shadow.


14 VARNISHING

Varnishes must protect the paint surface, must not darken, must be long-lasting and must be visually satisfactory.

I use MS2A throughout, or a Ketone Resin N if MS2A is not available, applied as a first coat by brush to give a saturating and protective coat. Further layers are sprayed, and a final wax polish is applied with a pad made of cotton velvet to protect the varnish against humidity and friction.

During the inpainting process, it is advisable to work on a fairly saturated varnish layer which brings out the original colors and thus facilitates matching.

Before he applies the final varnish, the restorer has to decide what visual effect he considers desirable for that particular painting. As a general rule a satiny sheen is to be aimed at, but dark paintings are flattered by a somewhat shinier varnish than light ones, and highly textured surfaces must be kept a little more mat to avoid sparkly reflections.

The degree of shininess of the varnish applied with a spray gun is a function of the following variables, and changing any one of them will change the appearance of the varnish surface: Viscosity of varnish

thicker = more mat.

Temperature of varnish

colder = thicker = more mat

Spray gun nozzle opening

smaller opening = smaller varnish droplets = more mat

Distance of nozzle from painting

greater distance = drier varnish droplets = more mat.


15 CONCLUSION

Perhaps one may sum up Helmut Ruhemann's feeling about his work as follows:

‘The restorer is a servant of the painter. He must strive to acquire technical skill and the ability to use the best methods available, in order to be able to make the painting again express the vision of the painter.’

This can never be done with total success. However, his methods as they are described here, and have been developed since, always had this aim in mind, and he achieved a degree of perfection which must fill one with admiration.


16 DESCRIPTION OF PHOTOGRAPHS

35mm slides are available from the Office of the Editor, 219 McDowell Hall, University of Delaware, Newark, DE 19711. A check for $9.00 should be made out to American Institute for Conservation.


16.1 PLATE 1.

A reconstruction carried out in monochrome undermodelling.


16.2 PLATE 2.

The Turbid Medium Effect.

  1. Dark Ground
  2. Light Ground
  3. Layer of Turbid Medium (as for instance oil paint).

The same layer of turbid medium appears cool grey in color on the dark ground, warm pink in color on the light ground.


16.3 PLATE 3.

The Structure of an Oil Painting, and the Repair of a Damage.

  1. Canvas
  2. Oil Ground and Drawing
  3. Underpaint
  4. Design Layer

  1. Fabric Inlay
  2. Filling
  3. Ground Color and Drawing
  4. Underpaint
  5. Design Layer


16.4 PLATE 4.

The Structure of an Early Italian Tempera Painting, and the Repair of a Damage.

  1. Panel
  2. Gesso Ground
  3. Bolus under Gilding
  4. Underpaint
  5. Monochrome Undermodelling
  6. Color Glazes

  1. Panel
  2. Gesso Filling
  3. Drawing and Bolus
  4. Underpaint
  5. Monochrome Undermodelling


16.5 PLATE 5.

Damage to the Design Layer of an Oil Painting

  1. Total LossDesign layer lost, underpaint damaged.Underpaint repaired in pva (AYAC) or MS2A.Design layer inpainted in Paraloid B72.
  2. WearWear in panels, showing dark streaks of wood grain, and streaks painted out.Wear in canvas painting, showing dots of underpaint, and dots painted out.
  3. CrackingFine cracking, and cracks interrupted where too obtrusive and at some intersections.Wide cracking treated like damage; underpaint repaired, and cracks inpainted in Paraloid B72.
  4. Glazes MissingGlazes totally worn away, revealing undermodelling.Glazes replaced in Paraloid B72.
  5. Highlights MissingHighlights totally worn away.Highlights scumbled on in very dry Paraloid B72.
  6. Patches of Alien ColorPatches of old overpaint, stains or fly specks.Patches inpainted with underpaint color in MS2A or pva (AYAC).Design layer glazed on in Paraloid B72.



REFERENCES

Conservator and Restorer of Paintings, The White Cottage, Brookshill Drive, Harrow Weald, Middlesex HA3 6SB, England.

Section Index

Copyright 1977 American Institute for Conservation of Historic and Artistic Works