Restoration of paintings - Procedures and techniques

The restoration of paintings on canvas and wood

The restoration of the paintings constitutes the set of operations aimed at prolonging the life of the artefact and implies an intervention on the material. By extension with “restoration” we mean the result of the intervention and also the part subjected to restoration. According to the Charter of the Conservation and Restoration of Art and Culture Objects (1987), the term identifies “any intervention which, in compliance with the principles of conservation and on the basis of previous cognitive investigations of any kind, is aimed at returning, as far as possible, the legibility and, where necessary, the use of an object”.

Beyond a precise or generic formula, the term painting restoration opens up to multiple definitions, implying not only technical-scientific methodologies but critical-aesthetic parameters, for which, by way of example, the well-known definition given by Cesare Brandi applies: “Restoration constitutes the methodological moment of recognition of the work of art in its physical consistency and in the double aesthetic-historical polarity in view of its transmission to the future “.

In the restoration of paintings it is customary to refer with the following expressions – also discussed and contested in various fields – to two main phases of intervention: aesthetic restoration (intervention on the image) and conservative restoration (intervention on the structural material).

With “aesthetic restoration” we refer generically to operations not directly aimed at consolidating the material part of the work, as in conservative restoration, but aimed at restoring legibility to the work, such as the operations of cleaning and of pictorial reintegration. These actions are characterized by the need to combine technical-scientific methodologies with reflections and therefore choices depending on critical-aesthetic factors, according to a way of proceeding particularly characteristic of the Italian school of restoration.

The “conservative restoration” is instead the restoration intervention that is limited to consolidating the existing, excluding reconstruction or reintegration operations (as in the case of aesthetic restoration). In the restoration of paintings, for example, the operations identified with the expression are essentially aimed at consolidating the support, the preparation and the color, or interventions aimed at improving the mechanical characteristics of the product and at blocking, as much as possible, the chemical-physical and biological degradation processes in progress.

Cennino Cennini – Giotto’s technique

7 May 2019

The Book of Art, written towards the end of the Fourteenth Century by Cennino Cennini, still remains the primary source for the knowledge of the artistic techniques of the Fourteenth Century. The composition was outlined with willow charcoal, darkening the folds and faces, then the tablet was dusted ...

How to prepare gypsum with rabbit glue

14 April 2019

How to prepare gypsum for in-filling and for the preparation of gypsum and glue: weigh 10 grams of rabbit glue in grains or ground, and put it to soak for a few hours ...

Pouncing – Video

6 March 2019

The technique requires the sheet to be placed on the surface and then beaten with a bag containing coal dust (or a colored pigment) along the perforated outline of the drawing itself.

Giovanni Bellini – Tempera grassa and mixed media

21 February 2019

In the paintings of this period there is a use of new techniques: oil emulsified with egg (tempera grassa) and also a succession of layers in tempera and oil (mixed technique).

Giovanni Fattori – The macchiaioli technique

8 February 2019

Giovanni Fattori's technique involves a drawing executed directly on the surface of the wood without any preparation. The support is often obtained from cigar boxes ...

Fake, copy, imitation, forgery and tampering

3 February 2019

La falsificazione artistica non si identifica semplicemente con la frode commerciale, in realtà essa è, prima di tutto, un fatto culturale in quanto nasce sempre da un preciso contesto culturale

History of artistic diagnostics

14 September 2018

Si dice che il pittore bergamasco Fra’ Galgario possedendo un dipinto tizianesco avesse compiuto dei tentativi di “esami stratigrafici” giacché con “un coltellino aveva indagato la struttura degli strati pittorici”.

Preparatory drawing

20 April 2018

The preparatory drawing is carried out, by means of the contour line to which chiaroscuro can be added, using a liquid or dry medium. A scheme of materials and procedures ...

Decorative interventions – Video

11 April 2018

Paste-print reliefs, insertion of glass stones, engravings, punching, graining and other procedures used in the gilding of paintings to obtain the maximum brightness and splendor of the surface.

Graffito in gilding – Video

25 March 2018

A technique used in gilding, "graffito" allows to obtain small highlights or gilded decorations on colored backgrounds.

Shell gold technique – Video

25 March 2018

Shell gilding or "nicchia" (niche) gilding is achieved by mixing gold dust with a binder and then spreading the mixture with a brush.

Oil gilding – Video

18 February 2018

Among the various techniques used for the gilding of a painting, the oil gilding technique involves the use of an oleo-resinous mordant to allow the adhesion of the gold leaf.

Water gilding – Video

9 February 2018

Among the techniques used for the gilding of a surface, water gilding, or bolus gilding, is the most widespread and appreciated.

Color alterations

14 January 2018

The primary function of the finishing varnish layer is to protect the paint from external agents. Contact with air and pollution can lead to ...

Priming – Video

11 January 2018

In modern and specialized literature, the term "primer" indicates the finishing layer of a preparation, characterized by limited thickness and a smooth and uniform surface, in order to facilitate the gliding of brush strokes.

The mestica – Video

17 November 2017

The "mestica" is a colored primer characterized by the use of fatty substances, clay, fixed oils or greasy paints, however quite distinct from the most ancient gypsum and glue preparation.

Gypsum and glue ground preparation – Video

17 November 2017

The operational precepts are extensively described by Cennino Cennini (The Book of Art, late Fourteenth Century) who, specifying the various fundamental phases for a preparation with gypsum and glue, handed down the customs typical of Mediterranean countries.

Tracing – Video

8 November 2017

Tracing has been one of the most popular techniques to transfer a drawing to a new support without changing its scale. Already used in the Thirteenth - Fourteenth Century workshops, the system is well attested throughout the Renaissance ...

Perspectographs – Video

7 November 2017

The tools used to verify the correct two-dimensional representation of forms in physical space used from the Fifteenth to the Eighteenth Century.

The darkroom – Video

7 November 2017

Darkroom, a more or less complex optical device that allows the painter to translate the complexity of a three-dimensional figure on a two-dimensional surface.

Squaring – Video

7 November 2017

The squaring, a system of carrying over the drawing, mostly aimed at its enlargement, based on the ratio of the squares measured on the original and those traced to scale ...

Raphael – Oil painting in Italy

11 May 2017

"It was a beautiful invention and a great commodity to the art of painting to find the color in oil", said Giorgio Vasari. Indeed the new technique ...

Vermeer – The Seventeenth Century in Holland

23 April 2017

Bright colors, prominency of light elements and transparency of shadows painted on a brilliant primer are the distinctive features of Flemish painting. During the Seventeenth Century ...

Lining

16 April 2017

The lining operation is performed when the canvas originally used as a support for a painting has lost its load-bearing power (due to the degradation of the cellulose, due to tears or large lacerations ...

Consolidation and color fixing

16 April 2017

The term consolidation refers to all those operations aimed at restoring a sufficient degree of cohesion in materials that have undergone a ...

Interventions on wood supports

16 April 2017

Interventions on the wooden support. Contrary to common beliefs, wood is a very resistant material: its degradation is not in fact due to intrinsic causes but to the environment ...

Removal of overpaint

15 April 2017

Much of the damage that can be found today on ancient paintings is due to the widespread use in the Eighteenth and Nineteenth Centuries of caustic alkalis (caustic soda, caustic potash) or other substances ...

Varnishing

15 April 2017

The application of a final varnish on the restored painting has the function of protecting the color from external agents and improving the optical characteristics of the object, giving it the necessary ...

Pictorial restoration

15 April 2017

Max Friedlànder (1867-1958) argues that the art historian - for whom the work of art is a document - can fully oppose any restoration that goes beyond conservation and removal ...

Overpainting and skinning

15 April 2017

Much of the damage that can be found on the paintings today is the result of ancient cleaning operations. Between the Sixteenth and Eighteenth Centuries no distinction was made on the type ...

Flaking and color loss

15 April 2017

The mechanical tensions that the support undergoes over time generate cracks (craquelure) that affect all the layers of the painting (preparation, paint film, varnish) and that ...

Support deformations

15 April 2017

The dimensional stability of the support is of fundamental importance for the preservation of the overlapping layers of color and ground preparation; it is linked to deformations ...

Damage to canvas supports

14 April 2017

The sensitivity of the canvas fabric to variations in humidity causes loosening, traction and uneven tension. A constant control of the painting over time (and above all relative humidity) ...

Biological damage

14 April 2017

Biological damage, attacks by biotic agents, ie living organisms, which in paintings on a wooden or canvas support appear as fungi (molds), bacteria and insects.

Simone Martini – Egg Tempera

12 April 2017

The painting of the skin tones, which, according to Cennini's painting rules, is the final operation, requires a green base which, obtained with green earth and lead white ...

Caravaggio – The Seventeenth Century technique in Italy

11 April 2017

There is a close relationship between the ground preparation and the technique of applying the color. With the spread of the free canvas on the stretcher support, this relationship ...

Tiziano – Oil painting on canvas

11 April 2017

Paintings on canvas were already fairly widespread in the Fifteenth Century: while in Italy Cennino Cennini had already described the way to give an adequate preparation to the canvas with a ...

Crivelli – Mixed media

11 April 2017

The use of a mixed technique can be recognized for most of the paintings between the Fourteenth and Sixteenth Centuries: in fact, if we define the paintings whose only binder is egg yolk as "egg tempera" ...

Botticelli – The tempera grassa

10 April 2017

The transition from egg tempera to oil technique was, unlike what is usually thought, particularly slow and gradual and meant much more ...

Damage to wood supports

9 April 2017

The most serious damages found on painted wood tablets are always to be attributed to the direct or indirect action of the wooden support. The layers of preparation and color, while being strictly ...

Van Eyck – Oil painting in Flanders

29 March 2017

Flemish painting of the Fifteenth Century is characterized by a limpid and glazed material obtained by successive superimpositions of thin mixtures. The oil binder ...

Infrared color photo

26 March 2017

Infrared color photo. The color photograph will be split into three distinct images (blue, green, red) with the command "split channels". IR False Color Tutorial ...

Fakes in art

24 March 2017

The phenomenon of falsification requires reflection on the material aspect of individual works of art. Modern art history studies are developed following different methodologies, all ...

X-ray radiography

24 March 2017

/

1 Comment

The X-ray radiography allows to investigate the deeper structure of paintings on canvas and wood, a preparatory drawing executed with a lead tip ...

Transmitted light

24 March 2017

Using a beam of light that passes through a painting on canvas placed between the light source and the observer, various information can be obtained both on the preparation and on the ...

Macrophotography

24 March 2017

Macrophotography should not be considered an important investigation technique only when it is combined with other examinations: the possibility of isolating small areas of the work and ...

Infrared photography

24 March 2017

The electromagnetic radiation that the human eye perceives is included in a wavelength range between 400 and 750 nanometers approximately. Beyond these limits, radiation ...

Infrared reflectography in paintings analysis

22 March 2017

Infrared reflectography has established itself as the most effective investigation technique in revealing the presence of preparatory drawings on the ground preparation.

Raking Light

20 March 2017

The first step to be taken when examining a painting with the aim of obtaining new information and investigating its state of conservation and technique: the raking light.

Ultraviolet fluorescence

17 March 2017

By projecting a beam of UV rays on the surface of a painting we will be able to observe how some parts of it light up while others remain dark. This is due to the phenomenon of ...

Craquelure

16 March 2017

As soon as the painting is finished, regardless of the technique used, it begins to deteriorate, both due to the action of environmental agents and due to its own intrinsic instability.

Diagnostics – Introduction

16 March 2017

Knowing the tools means, above all, knowing how to evaluate the potential in relation to the purposes to be pursued, in order to correctly use the tools ...

Pictorial inpainting methods

16 March 2017

The pictorial reintegration restoration of a pictorial surface is aimed at recreating a chromatic and formal connection between ...

In-filling

15 March 2017

The stucco is a mixture consisting of a binder and a powdery or granular charge, generally gypsum and animal glue (but also slaked lime, marble dust, sand, etc.) dissolved in ...

Relining methods

15 March 2017

In the restoration of paintings, relining or lining, is the operation aimed at consolidating the canvas of a painting by applying a new canvas on it using adhesive materials.

Cleaning

15 March 2017

By cleaning a painting we mean: - the removal of surface stains - the removal of surface dirt - the removal of overpaint - the removal of altered protective layers ...

Invasive analysis

15 March 2017

The investigation techniques applicable to works of art are divided into two classes: invasive investigations that require taking a sample and ...

Ground preparations – Introduction- Video

15 January 2017

Layer or set of the first layers of material applied to the support to obtain a suitable surface for pigments according to the painting technique adopted.

The importance of examining the pictorial material and the creative path in evaluating a work of art

The contributions that treatises offer to the study of artistic techniques must always be compared and integrated with the data obtained through a careful visual analysis aimed at evaluating the changes that the materials may have undergone over time both due to natural alterations and the action of man: many incorrect evaluations are due to a poor consideration of this aspect [1].

There are not a few historiographical theses that are based, paradoxically, on wrong restorations. This is the judgment attributed by critics and art historians to heavily repainted works that were therefore no longer able to express their original meaning [2]. As Stefano Turchetti keenly points out “the restorer must be at least a bit of an art historian, just as the art historian must be a bit of a restorer in the sense that he should at least be able to “see” a restoration, to know how to read it, in short have an eye trained to do this without of course having to act on the work. It has happened that art historians made attributions basing their theses on the restored or repainted parts of a painting. “In the past” there was a tendency to intervene on a painting to make it enjoyable “without taking into account that the painting must be respected and not transformed”. We therefore understand the importance of documentary research on past restorations as it emerged from the archives and from the reports on the restorations carried out in recent times.

The use of hot lixivia

Much of the damage that can be found on the paintings today is in fact the consequence of ancient cleaning operations. Between the Sixteenth and Eighteenth Centuries no distinction was made as to the type of dirt to be removed and each recipe could be used indifferently both on frescoes and on panel paintings.

Skinning caused by interventions with aggressive substances

Since the first written prescriptions, dating back to the Sixteenth Century [3], the use of hot lixivia was often recommended, produced from oak “hard ash” combined with quicklime [4]. Adding other substances (such as soap, eggs, salt or honey) this mixture was applied to the paintings with a sponge and removed with another sponge soaked in water as soon as the work appeared to be clean. Together with the dirt and the paint, the substances actually attacked the binder, breaking it up in depth and continuing to act for a long time even after the apparent washing. Thus the pictorial layer, devoid of the element of cohesion, pulverized and detached itself.

Soda, potash, ointments, urine and wine spirit

In addition to the use of reactive solvents (such as caustic soda and caustic potash) or other basic and acid corrosive substances, the techniques and materials adopted to obtain rapid results were extremely varied. We know of the practice of spreading hot strong carpenter’s glue on the painting, which after drying was then stripped off with all the dirt [5], or the use of “ointments” with imaginative compositions (it is not uncommon to find urine there) [6] or, again, of various abrasive substances. We also know of the practice of wetting the painted surface with wine spirit and then setting it on fire in order to soften the layers to be removed.[7]. The mechanical action of sponges and brushes rubbed on the surface during the application and removal of the various concoctions played a decisive role and, probably, caused the greatest damage [8]. The surface of the paintings that were treated in this way in ancient times has more or less deep abrasions, particularly at the crossing points of the craquelure lines, which give the whole work a pitted appearance (skinned surface) and are characterized by visible phenomena of skinning.

Lard rind or onion

Among these incorrect cleaning methods we also remember the widespread and harmful practice aimed at making the painted surfaces shiny: before important religious holidays it was, for example, customary to rub the paintings with the rind of the lard or even to clean them with onion[9] and wet them with boiled linseed oil, treatments that, while offering immediately captivating results, over time led to the formation of thick dark crusts. Furthermore, once the cleaning operations were completed, there was rarely any remorse in repaintings that would revive the colors and update the work to the taste or iconography of the moment; indeed, often the “restoration” intervention was identified with the repainting of the dirty parts [10]. The respect for the work of art felt as a historical and cultural testimony was actually still far from affirming itself: to this we can attribute, as Secco Suardo denounced in the Nineteenth Century, the endless number of paintings “barbarously not only peeled but flayed” [11], then serenely repainted [12].

Tampering

In addition to the concealment of the wear caused by persistent cleaning, we can distinguish other causes that may have led to a repainting.

Often there was a need to intervene on a natural aging phenomenon or on an accidental alteration judged unsightly (such as tears, lacerations, cracks, etc.).

Complete modification of the composition

In other cases, partial or total modification of the composition was used for aesthetic, historical, political, religious or commercial purposes, with the aim of meeting the client’s taste changes or market needs.

In this way, works largely tampered with have come to our days which, rather than documenting the figurative culture of the century in which they were made, testify to the taste with which the ancient work was reinterpreted in the particular period in which they were ‘restored’.

Repainting and glazing

The ability to recognize non-original parts is generally referred to more or less vast gaps and extensive repainting but in modern restoration (only apparently less invasive) the attention must be shifted to cases in which light, reversible and apparently harmless glazes are applied which can equally distort the expression of a face or the chromatic transition between two backgrounds.

This type of retouching is the most subtle since it is often indistinguishable to the naked eye and to normal photographic reliefs.

Dismemberments, downsizing, transport

In addition to these alterations to the original appearance of the pictorial surface, other types of tampering carried out in the past must also be taken into consideration that may have led to a misleading reading of the work: dismemberment of polyptychs with replacement of frames, reduction of the size of the work (most of the time to adapt them to new environments or to obtain uniformity of measurements in a collection), replacement of the support (numerous paintings on wood were, in the past, “transported” to canvas), alterations of the original color by applying paints of yellow-brown hue on the pictorial surface.

Masters of art and science

As for the natural alterations not due to human intervention, i.e. the transformations that the materials of the work undergo with the passage of time, we must keep in mind that the degree of alterability of a painting is often correlated to the degree of knowledge that the painter had of artistic techniques.

It is therefore meant that ancient art is based, taking up the words of Matteini and Moles, “on a complex of technological acquisitions whose relevance, today, we are hardly led to recognize. The great masters of pictorial art, in the Middle Ages and in the Renaissance, were largely also masters of science according to the meaning – commensurate with the knowledge of the time – that is attributed to this word today. Therefore, not only geniuses like Leonardo, the master of masters, systematically applied it in the art of painting, but also the majority of the great painters who today are recognized as leaders of a movement hardly neglected to rigorously implement the acquisitions then known to create a product not only valid under the aspect of expression but also technologically built in order to successfully overcome the degradation of time” [13].

The primary function of the finishing paint layer, to give an example of the above, is to protect the paint from external agents but also to modify the optical characteristics of the painted surface, influencing its final appearance. Any alteration of the paint layer will therefore reflect both on the aesthetics and on the state of conservation of the work and therefore also on the possibility of an incorrect interpretative judgment.

Ageing of the varnish

With the aging of the material there is a loss of flexibility and transparency: the paint film becomes dark, hard and brittle and, consequently, unable to resist the penetration of particles and external agents.

Alteration of the protective varnish

The colors, in general, lose depth and contrast and the painting appears of a yellowish-brown hue. The tiny cracks in the paint film, the gradual yellowing and the loss of transparency are due to both oxidative and photochemical processes but also to mechanical stress.

A less serious alteration that does not involve, as in the previous case, the need for partial removal and replacement of the paint is the so-called bloom effect, which can often be simply treated by smoothing the surface with a chamois hide. The term, from English, defines the whitening effect that can develop, in conditions of relatively high humidity, on a painted surface. The phenomenon initially takes the appearance of a bluish halo due to the dispersion of the light beam on the tiny drops of water trapped in the layer by condensation. Among the paints, those based on mastic resin easily give rise to the bloom phenomena, while there is a lower predisposition with the use of dammar .

The death of colors

As for the premature ageing of the painted surface, this can be caused by the choice of an unstable binder. In this regard, the passage in which De Mayerne describes the loss of color caused by the excessive darkening of the binder oil, which generates the formation of a brownish plasticized patina, [14] and therefore the consequent alteration of the original color: “the death of the colors occurs when the oil floating on the surface dries up and forms a skin that blackens in contact with the air” [15].

As Alessandro Conti has acutely pointed out in many of his pages [16] he natural aging of a well-packaged oil instead generates a warm yellow or brown tonal unit which, by lowering the light colors and lightening the dark backgrounds, can soften the original chromatic crudeness of a work.

“Over time, the color timbre and the overall effect of a painting is bound to change” [17] and a testimony that does not allow doubts on the actual trust that the artists placed in time is provided by André Felibien des Avaux:

“I will tell you that it is for the same reason of this great union of the coloring that the excellent oil paintings, and executed a long time ago, present themselves with more strength and beauty because all the colors with which they were painted have had more ease to unite, merge, mix with each other as the most watery and humid was present in the oil dried” [18].

The presence of a uniform layer of paint in good condition slows down the degradation processes to which the pigments present in the paint layer are normally subjected to. Each individual pigment particle is then wrapped in the binder, whose nature and state of conservation will also participate in slowing down the action of light, air and pollutants. These, in conjunction with humidity, tend to change the properties and composition of each individual pigment. Color alterations are in fact caused by chemical or photochemical phenomena. Some pigments, especially those that contain organic substances such as garanza lake or Indian yellow, are unstable under light; under the effect of violet and ultraviolet rays they therefore tend to turn pale. Other pigments of inorganic origin, such as verdigris, on the other hand, tend to become dark.

Contact with air and pollution can lead to other types of pigment alteration. We can, for example, mention the blackening of lead white or minium which, when combined with oxygen, are subject to oxidation reactions. The phenomenon is especially noticeable on wall paintings, where the protection of the binder is lacking and where humidity enhances the action of pollutants since, in addition to bringing them into solution, it acts as a means through which they come into contact with the work.

A final cause of the chromatic alteration of the pigments is linked to the chemical reaction (especially oxidation) triggered by other materials to which they have been associated (another pigment, the binder, the filler present in the preparation, a product added in the restoration, etc.). Natural ultramarine blue, for example, tends to turn gray in contact with lead white.

Some pigments, then, are attacked by the lime and therefore cannot be used in the fresco technique. Others, on the other hand, change rapidly in oil techniques: smalt blue, for example, was carefully avoided in oil paint because it decomposes releasing soluble cobalt which causes intense oxidation of the oils.

Finally, there is a last case of chromatic alteration to which many oil paintings are subjected which, if not correctly interpreted, can lead to stylistic evaluation errors and is given by the use of primers and colored preparations.

From the second half of the Sixteenth Century, the preparation on which the color was applied began to be mixed with earths and other opaque pigments. While preventing the maximum luminosity obtainable through the transparency effects of the colors on the white background, these preparations offered considerable advantages and, first of all, provided a medium tone as a base that allowed the artist to work simultaneously in both light and dark tones: immediately, with a few brushstrokes, the image was rendered in three dimensions with particularly marked chiaroscuro effects, conforming to the taste of the time.

However, it was necessary to paint with full-body strokes of color also to avoid the inconvenience of the progressive disappearance of the mid-tones because of the transparent background color due to the inevitable increase in transparency over time of the layers of oil paint.

The accentuated chiaroscuro effects that many works today show is therefore not due to the artist’s will but to the gradual disappearance of the half tones that the underlying dark preparation has “eaten”.

Manfredi Faldi, La documentazione materiale come supporto e verifica dell’analisi storico-stilistica nelle opere pittoriche, Florence 2003

[1]Cfr. M. Matteini, A. Moles, Il Laboratorio scientifico nella ricerca e nella prassi operativa del restauro dei dipinti, in Problemi di restauro. Riflessioni e ricerche, Firenze, EDIFIR 1992, p. 213

[2]Cfr. Veronica Briganti (a cura di), Intervista a S. Turchetti, BTA – Bollettino telematico dell’Arte, n. 9, 14 novembre 1994

[3]Si veda il Manoscritto Palatino 1001 della Biblioteca Nazionale di Firenze descritto in I Codici Palatini della Biblioteca Nazionale Centrale di Firenze, Roma, 1890-1940, II, pp. 476-7: “A far nette le figure in muro e in tavola che pareranno nuove. Recipe ceneri di rovere et tanta calcina et messedate ogni cosa insieme, poi fattene lissia caldata, poi pigliate del miel, sapon negro, et rosso di ovo, tanto di uno come dell’altro et fatte che ogni cosa sia insieme incorporata poi con questa lissia distemperata et con questa fregate ch’è cosa provata”. Questo ricettario si trova parzialmente riprodotto nello studio di A. Conti, Storia del restauro e della conservazione delle opere d’arte, Milano, Electa 1973, pp. 92-94

[4]Si veda Max Doerner, The Materials of the Artists and their uses in painting, New York, Harcourt, Brace and Company, 1949, p. 401, dove si parla anche dei bagni di olio di lino bollito e degli olii grassi della cucina che venivano usati per fare aderire i colori che erano stati indeboliti dall’uso della lisciva.

[5]A. Conti, cit., 1973, p.103

[6]Cfr. T. T. De Mayerne (1646), a cura di S. Rinaldi, cit., 1995, p. 163 e 250 (corrispondenti al f.56v e 145v del Ms. Sloane 2052).

[7]Cfr. quanto riportato da G. Secco Suardo ma si cita, qui e altrove, dalla ristampa anastatica Hoepli, Milano 1979, pp. 369-70: “il celebre prof. Giuseppe Guizzardi bolognese (…) poneva il suo quadro orizzontale, e con della creta vi formava tutt’attorno una specie di argine alto un dito, e costrutto in modo che non potesse scolarne un liquido. Vi versava allora dell’ottimo alcool, poi vi dava fuoco: e con un panno bagnato disteso fra le mani stava osservando l’effetto di quella fiamma: e quando, a suo avviso, era giunto il momento opportuno d’un subito vi stendeva sopra quel panno spegnendo immediatamente il fuoco.”

[8]Si confronti in particolare quanto descritto da Ulisse Forni, cit., 1866, p.127 e S. Suardo, 1866, ed. cons. Hoepli 1979, pp.364-5

[9]Si veda a proposito G. Secco Suardo,1866, ed. cons. 1979, p. 323

[10]Cfr. A. Conti, cit., 1973, p. 36

[11]G. Secco Suardo, cit., 1866, ed. cons. 1979, p. 42

[12]Si veda anche l’intervento di Silvia Bordini, Vernici e restauri nel Settecento: la Lettera sopra l’uso della vernice sulle pitture di Filippo Hackert, in “Problemi del restauro in Italia”, Atti del Convegno Nazionale, Roma, 1986, pp. 163-274.

[13]Cfr. M. Matteini, A. Moles, Tecniche della pittura antica: le preparazioni del supporto, in “Kermes”, II, n; 4, Firenze, Nardini 1989, p. 49

[14]Cfr. P. Carofano, Sulle ricette di pittura del trattato di Theodor Turquet De Mayerne, in “La Diana”, anno I, 1995, p. 164-5

[15]T. T. De Mayerne (1646), a cura di S. Rinaldi, cit., 1995, c.9v.

[16]Sul restauro, a cura di A. Conti, Torino, Einaudi 1988, si veda anche, dello stesso autore, Manuale di restauro, a cura di Maria Romiti Conti, Torino, Einaudi 1996

[17]C. Giannini, R. Roani, cit., 2000, p. 191 dove si legge anche che “l’espressione ‘tempo pittore’ è nata all’epoca del collezionismo barocco e non coincide con il gusto per la patina ma ne rappresenta un aspetto”.

[18]A. Felibien Des Avaux, Entretiens sur les vies et les ouvrages des plus excellens Peintres, anciens et modernes, vol. II, Paris, 1688, p. 240.

ORIENTATIVE BIBLIOGRAPHY

The sources and reference texts to the discussed topics.

The restoration of paintings on canvas and wood

The importance of examining the pictorial material and the creative path in evaluating a work of art

The use of hot lixivia

Soda, potash, ointments, urine and wine spirit

Lard rind or onion

Tampering

Repainting and glazing

Dismemberments, downsizing, transport

Masters of art and science

Ageing of the varnish

The death of colors

ORIENTATIVE BIBLIOGRAPHY

Recent articles

Recent video