Anna Perkins

Historical Practices

Overview

Before art conservation became a profession in its own right, works of art still incurred damage or aged into poor condition, and artists were often the ones tasked with their maintenance. A sculptor during the Renaissance would have been tasked, for instance, with making a new nose for a broken ancient Roman relic. Several centuries later, a museum boom in Europe prompted the hiring of artists to restore Renaissance art. Since these artists were concerned primarily with aesthetics, rather than structural repair, the science of materials, or the ethics of authorship, their restorations were focused on improving the appearance of the work and did not adhere to any set of standards. Many restorations that took place before the nineteenth century suffered from liberal overpainting with unstable and hard to remove materials, many layers of yellowed varnishes, and experimental methods of gluing, lining, and re-stretching paintings. ^{1, 2, 3, 4, 5}

At the beginning of the twentieth century, literature on the topic of art conservation started to be published. Once formal conservation schools were established and the International Institute for Conservation of Historic and Artistic Works was formed in the mid-twentieth century, conservation ethics and standards of care were communicated worldwide to conservation practitioners. The modern paradigm of art conservation became the adherence to key philosophies like minimal intervention, reversibility, and the stability of materials, akin to a doctor’s “do no harm” commitment. These principles recognize the ethical need for specific conservation expertise and caution when treating works of art, as conservators know that the artwork will continue to age and likely require, after some years, the removal of their work and the application of new conservation treatments.

Another Way of Learning

15th-19th Centuries

In the introduction to The Art of the Conservator (1992), a collection of case studies, Andrew Oddy provides a brief history of the profession of conservation. He writes, “With the establishment of both private and public collections or antiquities following the Renaissance in Europe [15th-17th cent.], the demand for ‘restoration’, rather than ‘repair’ of antiquities began to increase, and the foundations of the conservation profession began to be laid.”⁵

Since conservation was not yet a distinct profession, the restorers were “craftsmen who made similar objects themselves.”⁵ These practitioners “renovated” the artworks, according to Oddy, “because their main aim was to disguise [that] the object had ever been in need of restoration.”⁵ Likewise, conservation researcher Matthew Moss describes the continual “updating” of works of art, even if they did not particularly need repairing: “The style of painting done at a particular time might eventually go out of fashion….[A]rtists often repainted portraits to mirror changes in dress style.” During the Renaissance, restorers were often “distinguished artists,” whose efforts to cover damage “sometimes covered large areas of the original work,” but by the nineteenth century, “often very minor craftsmen carried out restoration to old master paintings and modified the appearance of the original,” according to Moss.⁴

Oddy defines “conservation” as “preserving the man-made remnants of the past” and “repair” (according to The Concise Oxford Dictionary) as “to restore to good condition, to renovate, to mend, by replacing or refixing parts or compensating loss.”⁵ Oddy points out the language difference between “repairing” a functional object with “restoring” a decorative object, that we conceive of the action of “restoring” or “conserving” as weightier and requiring more consideration than “repairing.”

The language shift from “repairing” to “restoring” coincides with the development of conservation as a profession, according to Oddy. He describes how the profession gradually became more scientific alongside technological developments. Ethics became more consistent with the creation of formal training programs and shifting societal attitudes about historical works of art. Similarly conservator Stephen Gritt writes, “What seems to characterize the writings and commentaries as the [19th] century progresses is a gradual increase in professionalism, a greater scope of thought, increasing scientific research, and, to some extent, a certain amount of codification of practice.”¹

In her article, “Retouching Paintings in Europe from the 15th through the 19th Centuries: Debates, Controversies, and Methods,” conservator Wendy Partridge conducts a brief literature review of retouching practices from the fifteenth through nineteenth centuries, highlighting examples of “contemporary” conservation practices that predate the modern era. She writes, “We often think of retouching from the past as being sloppy, heavy handed, and unsympathetic to the painting, making wholesale changes for reasons of taste and marketability. In fact, there are many examples of this type of work, but this is not the whole story.”⁶

Moss offers some examples of the unfortunate materials and heavy-handed practices of these early restorers in his book, Caring for Old Master Paintings. He notes that in the sixteenth century, caustic soda and nitric acid were used to clean grime and discolored varnish from Jan van Eyck’s Mystic Lamb, causing extensive damage to the painting.⁴ In the sixteenth and seventeenth century, black soap, urine, and abrasives like pumice were recommended for cleaning paintings.⁴

Whereas many restorations in the sixteenth century were intended to update the (often religious) imagery, intentionally obscuring original paint in addition to hiding damage, “by the late Renaissance there are examples of faithful reconstructions of the original composition.”⁶ Partridge writes that historians like Alessandro Conti in Storia del Restauro (1988) have found examples of “the occasional use of reversible retouching materials in the 17th and 18th centuries, and the search for stable materials in the 18th and 19th centuries.”⁶

Interestingly, Alessandro Conti and Roger Marijnissen have found examples of individual conservators from the seventeenth through nineteenth centuries practicing more “modern” approaches to conservation.¹³ Due to the lack of formal training, most restorers during this period did not consider the permanence of their interventions, but a few did consider using reversible materials. Similarly, whereas most restorers would overlap original paint in order to more easily make the inpainting seamless, a few restorers were more discerning about paint placement. In her article “Approaches to the Reintegration of Paint Loss: Theory and Practice in the Conservation of Easel Paintings,” conservator Kim Muir summarizes:

Partridge outlines that the development of conservation as a profession and the interdisciplinary training required resulted in a knowledge base where principles like “less is more”, meaning minimal intervention and retouching, naturally arose. Partridge writes, “By the end of the 18th century, specific training and skills were suggested for inpainting, including the knowledge of old master techniques and chemistry. In the 19th century, a ‘less is more’ principle was articulated, an apparent response to a purist aesthetic that suggested leaving losses visible.”⁶

In addition to technological development, public backlash against conservation projects, even if misplaced, may also have contributed to the development of standard practices and ethics. Former director of conservation at the National Gallery of Canada Stephen Gritt describes an 18th century conservation controversy: When state-sponsored Italian restorers cleaned too aggressively for public sensibility, viewers felt that, in removing the patinaed varnish, conservators had also removed the top layer of the artist’s work, and that the discolored varnish was an inextricable part of the authentic work.¹ Gritt comments, “It was stated explicitly that patina should be preserved for sensible practical reasons to avoid changing or damaging a painting. In this, the notion formally accumulated one of its more complex connotations: that it is a marker of ‘authenticity.’”¹

This perception of the authenticity of patina was sometimes explained by claims that the artists designed this effect based on their understanding of the aging of materials. Challenging the sentiment that artists painted in anticipation of how their work would change over time, Gritt shares a passage from William Hogarth’s Analysis of Beauty (1753). Hogarth notes that all of the different pigments and materials used with their different fading or yellowing rates would confound the artist’s theoretical attempt to foresee the aging process. “Therefore how is it possible that such different materials, ever variously changing…should naturally coincide with the artist’s intention.”¹ Similarly, conservator Barbara Appelbaum asserts that “there is no evidence to date that an artist has ever made a piece brighter than desired….[P]eople…have consistently chosen the brightest colors which they could get.”¹²

Prior to the mid-nineteenth century, professional restorers, as opposed to artists who restored, predominantly existed in Europe, according to Patricia Sherwin Garland, a conservator at the Yale University Art Museum. In her article “Tradition of Retouching Practices in America,” Garland writes, “The practice of conservation in America…was intrinsically tied to Europe.”⁷

Garland outlines that, in the early nineteenth century, there were a number of American artists who attempted restorations of their own works, primarily due to pigment fading or paint film cracking.⁷ Charles Willson Peale, known for painting George Washington and founding the Philadelphia Museum (and for naming his children after famous artists),⁸ “treated [his] own pictures, often attempting to correct problems with defective materials…Peale makes mention of paints that have faded and are too cool.”⁷ Garland writes that Benjamin West similarly painted over cracks in his own paintings, retouching which “clearly go[es] over and into a pattern of wide traction crackle, indicating that concealing the disfiguring crackle was the likely motivation for the retouching.”⁷

The concept of “less is more” also coincided with the museum and archaeology boom in the nineteenth century: “Works of art were increasingly valued as historical documents.”⁶ Damage, especially due to age, imparted historicity to a work of art because of its authentic, rather than deceptively repaired, appearance. The art historian Giovanni Battista Cavalcaselle argued in 1870 that broad overpainting practices were deceptive, even if the restoration improved the appearance of the work of art: “‘It does not matter if you recognize a restoration, in fact, you should be able to recognize it, since what is necessary is respect for the original work….A lie, even a beautiful lie, must be avoided.’”.⁶

Oddy writes that “little is known, or has been written, about the nineteenth- and early twentieth-century practitioners [of restoration] and their methods,” except for Friedrich Rathgen in Germany and a legacy of conservators at the British museum including John Doubleday.5 Partridge notes that conservation literature started to appear in the nineteenth century, along with cautions against retouching with oil paint due to its darkening over time, advice to inpaint over chalk filling materials, and experiments with mastic, tempera and watercolor as binders for inpainting.⁶ In his 1931 book Paints, Paintings and Restoration, Dr. Maximilian Toch, a chemist at a varnish manufacturer in New York and a professor of the chemistry of painting at the National Academy of Design, stated, “There is no systematic literature [other than his own] on the restoration of paintings, with the exception of a few chapters here and there.”⁹

While conservation principles were beginning to be outlined in the nineteenth century, their broad application had yet to take place. The lack of conservation standards can be demonstrated by the case of the James Jackson Jarves collection. Jarves, who later donated this collection of early Italian paintings to Yale University, commissioned many restorations while in Italy that were not well-documented. Yale conservator Mark Aronson characterizes Jarves’ 1850s interventions, “The restorations Jarves had done to his paintings while collecting in Italy are difficult to evaluate. He worked with Greek artist, dealer, and restorer Georgio Mignati, who…apparently restored some of the works…But lack of written or photographic records makes a characterization of Mignati’s practice guesswork.”¹⁰

20th Century

In the early twentieth century, Oddy describes that many works of art suffered from their storage conditions during WWI, leading to the British Museum’s creation of “a permanent scientific research laboratory for investigating the causes of decay and the methods of treating its effects.”⁵ In The Care of Pictures, conservator George Stout confirms, “Since 1948, many centers for [conservation] training have been provided.”⁵

After WWII, the IIC (International Institute for Conservation of Historic and Artistic Works), which publishes Studies in Conservation, was created, and national societies were created in many countries, such as the AIC in the US. Stout describes the IIC as “the qualified body of professional conservators.”⁵

Even after formal training programs were established, it took some years for fellow conservators to shake the “trade secret” mindset and to share knowledge and establish common practices. Oddy writes, “Even as late as the 1960s, those restorers who had trained before the Second World War often had their own secret way of doing jobs ad their own secret recipes for sticking, colouring, or patinating.”⁵

The IIC-American Group (which became the AIC) discussed the creation of a code of conservation ethics at their second ever meeting in 1961.¹¹ These conservators included Murray Pease, Sheldon Keck, and others who became known as the Murray Pease Committee. In subsequent meetings, the IIC-AG adopted and published their code of ethics in their journal, Studies in Conservation. In the preamble of the current AIC code of ethics, Elisabeth C. G. Packard writes of this original code, “The primary purpose of this document was: “to provide accepted criteria against which a specific procedure or operation can be measured when a question as to its adequacy has been raised.”¹¹ These standards of practice and ethics continued to be revised throughout the second half of the twentieth century until the 1994 edition, which is still in use today.

With the advancement of polymer technology in the twentieth century, an onslaught of new materials became available to conservators to test out. Oddy relates that instant join materials like epoxies and polyesters became popular structural repair adhesives. He also mentions that the onset of “protective coatings, corrosion inhibitors, surface active agents, complexing agents, bleaches and enzymes for stain removal, tarnish removers, and modern dyes and pigments,” along with developments in analytical instruments, have advanced the capabilities of art conservation.⁵

Beyond advancements in cleaning or inpainting techniques, examples of active conservation interventions, conservators increasingly became aware of the value of preventative conservation, a passive form of conservation, because of the environmental toll on paintings. In 1978, Garry Thomson published the seminal book on preventative conservation, The Museum Environment, which “clearly laid out the hazards to which museum collections are subject,” according to conservator Barbara Appelbaum in her own book on the topic, Guide to Environmental Protection of Collections (1991).¹²

Retouching

In “Approaches to the Reintegration of Paint Loss: Theory and Practice in the Conservation of Easel Paintings”, Kim Muir recounts the history of retouching approaches since the nineteenth century, focusing on modern approaches. She describes that because there are “inextricable links between materials and meaning in a work of art,”¹³ retouching includes a philosophical element, in addition to the scientific and artistic methodologies of conservation practices. She writes, “The literature on retouching falls at the intersection of theory and practice…Current trends in conservation research, which show greater interest in the subjective, culturally contingent factors that shape conservation theory and practice, have stressed the importance of an awareness of the historical and philosophical foundations of the profession.”¹³

Muir states, “Damage to the paint layer can result in a change or devaluation of the aesthetic, spiritual, historical or cultural meaning of the work.” Because of this “devaluation” of the work of art caused by damage, most of the history of painting restoration falls into the “complete reintegration” (or “imitative”) category, where the work of art maintains an undamaged appearance as much as possible, as opposed to “no integration” or “visible retouching” categories.¹³ “Complete reintegration” is the term for “emulating the appearance of the original painting as closely as possible”, whereas the “no reintegration” approach strips away past restorations to reveal the artist’s handiwork as much as possible and deliberately does not retouch losses, according to Muir.¹³

A notable example of the “no reintegration” trend in painting conservation was the cleaning of early Italian paintings, the aforementioned Jarves collection, at the Yale University Art Gallery in the 1960s. At curator Charles Seymour’s direction, conservators applied a “purist” approach to conservation that rejected retouching in favor of showing only original material, even if that material was very damaged.¹³ Past imitative restorations were removed, and the state of the original paint was controversially put on display, revealing the “truth” about the extent of the damage to the viewers.

Other conservators, like Helmut Ruhemann and Sheldon Keck (see “Inpainting Media” for more information) preferred to inpaint where the original paint had been lost in order to maintain the artist’s composition. Such inpainting was “imitative,” meaning it was designed to seamlessly blend in with the original paint and be undetectable to the naked eye, but these retouchings using reversible materials would be visible under UV lamps such that future conservators would be able to distinguish the retouching from the original paint.

An ideological compromise between imitative retouching and no retouching, “visible retouching,” as described by Italian conservator and art historian Cesare Brandi in the mid-twentieth century, involves retouching just enough to convey the meaning of the artwork without purporting to emulate the artist’s hand (e.g. Brandi painted in vertical lines that you can see when up close but not from a distance).¹³ This compromise allowed the effect of the painting to be maintained or restored without the “deception” of imitative restoration. Because Brandi’s Italian writings were not translated for many years, his ideas did not spread far and wide, and this method of retouching did not catch on in America.

Even still, Muir champions Cesari Brandi’s contribution to the philosophical conversation on retouching in the twentieth century. Brandi’s approach endeavored to “conceive [of] the work of art as an entity possessing both an artistic and a historical dimension,”¹³ Brandi wrote articles, gave lectures, and trained other conservators on his restoration philosophy in the 1940s-60s, pushing back against the “no integration” trend because, as per Muir, “the loss was not only a disturbing factor because it represented a gap in the image but because it could assert itself as a form within the composition.”¹³

Cleaning

Arguments about whether or not to remove patinaed surface coatings from paintings were not put to rest in the nineteenth century but continued into the twentieth century. Gritt observes a central conflict associated with the removal of patina – that we, the public, might find the work as the artist originally painted it garish without the “harmony” of the patina. He inquires, “[H]ow do we cope with the fact that the most prized residues of the best human activity may be very different from when they were made?”¹

In the twentieth century, the collective understanding of “authenticity” shifted from leaving the patina and aged qualities intact to removing the grime to better showcase the artist’s handiwork, which Gritt says led to over-aggressive cleaning projects in the mid-twentieth century. These campaigns led to the modern debate between total and partial cleaning approaches. One such controversial project, The 1947 cleaning of over seventy paintings at the National Gallery, London for “The Exhibition of Cleaned Pictures,” was so extreme that it prompted government inquiry, in which the conservator, Helmut Ruhemann, made public the documentation of his treatment to push back against the accusations that he ruined these paintings.^{14, 15} Through photographs, radiographs, laboratory notes, and other data, curator Philip Hendy and Ruhemann diffused much of the criticism levied against them that they must have stripped away original paint.^{14, 15} Stout adds, “A seasoned conservator knows that [they] cannot tell by looking at a picture whether is was in any way damaged by the treatment….Unless [they have] at [their] disposal evidence of its condition before and after treatment, [they do] not know enough to say whether or not the damage occurred at any particular time.”¹ Gritt summarizes the perceived errors of both ways of thinking: “At the heart of criticisms of the camp of total cleaning was the fear of removal of original material. At the heart of criticisms of mediating cleaning was the accusation of subjectivity and untruth.”¹

Gritt notes that, in the present, “the term ‘patina’ and its traditional accompanying connotations are no longer critical within discourse about the cleaning of paintings.”1 He attributes this change both to technological advancement and to attitude shifts about whether patina, darkening with age usually as the result of a varnish or dirt, improves the appearance of paintings. He credits scientific advances that have deepened our understanding of degradation, the methodology of conservation becoming more similar across institutions, and the development of technical art history as a discipline with the decline of strong or extreme stances on maintaining patina or undertaking total cleaning.1 He notes that the overall conservation trend has been toward presenting clean paintings, and this “information- or knowledge-based aesthetic for paintings…is a relatively new feature.”¹

Gritt takes as a case study of contemporary total cleaning the restoration of a Botticelli workshop painting with a gray surface layer. The National Gallery of Canada team diagnosed that this layer was distinct and added later than the original painting, and they tested various solvents to find the appropriate blend to remove the gray layer without damaging the surface of the original painting. He describes this process to highlight that, in the absence of risk, or in the presence of confidence in the methodology, the decision to intervene with a “total cleaning” approach was unanimous for the group of restorers and curators.¹

Gritt summarizes that “as our ability to safely clean paintings increases, aesthetic mediation during cleaning appears to diminish.”¹ He qualifies this statement by adding that “aesthetic mediation is certainly one aspect of the role of the restorer. To deny this would be illogical, given that what we do in cleaning and restoring paintings changes their appearance radically.”¹ He suggests that aesthetic discussions ought to find their way into the conservation discourse, as historically the aesthetic considerations have been very subjective, but now these discussions could be framed with technical knowledge and shared understanding of the risks of cleaning.

In contrast to Gritt’s confidence in the safety of contemporary restoration practices and his assertion that the cleaning debate is no longer relevant, fellow conservator Konrad Laudenbacher raises the alarm that restoration is “more than a great physical risk for the work of art; under certain conditions it can also cause significant changes in its aesthetic appearance and perception” and cautions the community about potentially unnecessary restorations undertaken only because of planned exhibitions.¹⁶ He warns that varnish removal is the most invasive restoration procedure and that solvents may come into contact with the original paint layers. His ethical concern that interventions take place, not because the condition of the painting warrants it, but because art owners want to display these works, is a great point. His concern about the cleaning of varnish, however, is certainly overblown, since aged oil paintings are insoluble in mineral spirits and other common conservation solvents. In The Care of Pictures, Stout writes, “Dried oils do not respond to even the strongest of organic solvents.”³

To provide historical context regarding the cleaning of paintings, Laudenbacher cites Doerner’s 1921 book The Materials of an Artist and Their Use in Painting, which describes that harsh solvents and soaps were used in the early 19th century along with many trade secret cleaning concoctions. Laudenbacher writes, “Caustics, acids, soaps, solvents, and ethereal oils were used…egg yolks, bread, vegetable juices, onions, garlic, and much more…Rubbing a painting with half of a potato is often suggested.”¹⁶ These materials and abrasive application techniques often stripped the actual paint layers to the point that extensive overpainting was necessary to restore the painting to good condition.

In the late 19th century, balsam, or tree sap, resins became popular cleaning agents for works of art on the recommendation of the chemist Max von Pettenkofer, but the treatment was not a panacea and was especially damaging to oil paintings. “Copaiba balsam is a resin now known for its softening properties that remain active over a long period of time. An original paint layer treated with copaiba balsam is thus much more sensitive and subject to future damage than prior to the intervention.”¹⁶ The writer offers another cautionary tale of over-trusting current scientific capabilities that cannot always anticipate the consequences of an intervention by briefly discussing the 1947 Cleaned Pictures exhibition at the National Gallery. While the cleaning paintings were thoroughly analyzed through all available test methods, the cleaning was controversial in its extensiveness.

Laudenbacher notes that the impetus for restoration is often an upcoming exhibition, rather than degradation, leading works of art, especially the most famous ones, to undergo restorations that may shorten the lifespan of the painting, as immediate damage may not be apparent, but interventions can have long-term consequences.¹⁶ He acknowledges that aesthetic trends in conservation exist and that the conservators, whilst doing their utmost to be unbiased, cannot escape the influence of their time and place. Laudenbacher explains that “these fashions still exist because conservators do not always recognize that they subconsciously apply contemporary taste to everything, including works of art, and that they are always dependent on current technical and intellectual resources and possibilities.”¹⁶

Re-Varnishing

After cleaning and/or retouching, a painting usually is re-varnished to protect the underlying paint from the elements. Only in the second half of the twentieth century have synthetic varnishes become available to conservators. Oddy, a British conservator, observes that synthetic resins such as adhesives and picture varnishes revolutionized conservation materials, as they were durable and did not discolor over time. He notes, though, that they are not perfectly ideal materials, in that there is always some drawback like irreversibility or interaction with the substrate. “[N]obody has yet produced the perfect adhesive which is colourless and easily reversible, does not react chemically with any object, does not discolour, become brittle or insoluble or lose its adhesive power on ageing.”⁵

Such a statement requires the qualification, though, that many synthetic binders when used in conjunction with hindered amine light stabilizers (HALS) and UV absorbers like benzotriazoles (UVAs) will not discolor, become brittle, or become insoluble for at least a hundred years in gallery conditions. Golden’s MSA varnish, as I well know, has gone through both exterior and accelerate aging testing and confirmed a lack of yellowing, cracking, and insolubility after such intense exposure. It is certainly true that many synthetic resins are not suitable for conservation, but there indeed are some robust materials, such as Aquazol, Paraloid B-72 and Regalrez 1094, among others, that conservators have thoroughly tested over forty or more years. While conservators boast broad understanding of materials, it is important to recognize that they are neither polymer scientists nor paint formulators, and their assertions about whether or not materials of certain criteria exist may become outdated quickly, as industrial coatings materials are continually innovated.

Oddy praises the first synthetic adhesive, cellulose nitrate, for mostly fitting the conservator’s bill, but he notes that it is controversial and has fallen out of common use.⁵ This inexpensive polymer was popular in the 1930s through 1950s, primarily as the material for photographic film, but was also used in coatings, such as clear varnishes for conservation.¹² Appelbaum describes cellulose nitrate as “a major headache,” since it discolors, develops surface defects, and ultimately deteriorates into a powder, releasing flammable and explosive gas.¹² Flammability is evidently not a desirable quality in a material that comes into contact with valuable works of art.

Like Oddy, Laudenbacher is skeptical of the claims of synthetic binders. Laudenbacher cites two studies (Koller and Baumer, 2001, and Nicolaus 1998) to disparage the general sense that synthetic varnishes are generally non-yellowing and removable. While there is some validity to this claim as explained above, Laudenbaucher misrepresents the quality of modern materials in that he ignores how truly awful many historical materials, such as damar varnish, which is still used by some traditionalist, and primarily European, conservators to this day, have proven to be. Damar, a natural resin soluble in turpentine, which is more harmful to human health than typical mineral spirits, is still used despite its known browning, embrittlement, and insolubility after only a few years.

On the contrary, Stout praises the inception of PVAc and acrylic binders in art conservation practices (see “Inpainting Media” for more information). He asserts, “On all the evidence available, those [synthetic binders] now known have a better chance of survival than the natural resins. They have no color, they get less brittle, and case of damage they can be somewhat more readily removed from the surface of the paint.”³

Laudenbacher cautions, “One should be careful not to rely entirely on science, which can convince us with unjustified certainty that currently available restoration materials and techniques are always much better than earlier methods.”¹⁶ While Laudenbaucher makes good point that conservators should not assume they know all there is to know about treating paintings, it is dishonest to suggest the inferiority of new materials, that there has not been overall progress.

We should indeed assume the future will reveal the drawbacks of current treatment standards, but the level of distrust that Laundenbacher conveys is fearmongering. While it is true that we are still waiting to see the long-term results of modern conservation treatments, this intense skepticism of science does not weigh the heavy drawbacks of traditional methods with known adverse effects against the much more minimal drawbacks of materials synthesized and designed for resolubility and longevity. His caution is admirable, however, as it makes clear that minimal interference with the artwork is “plan A.” He highlights the importance of condition reports that include historical details of the artist’s use of materials and past restoration work. He gives the sound advice, “[T]he goal should still be to proceed on a historical basis and from technical as well as aesthetic viewpoints. The motto should be ‘first observe, then act.’”¹⁶

References

Why Conserve? Condition Reports