The Getty Conservation Institute is currently conducting a research project that addresses one of the critical issues in conservation: the cleaning of surfaces of art objects. Cleaning the surface of an object—which ranges from dirt removal to replacing a degraded varnish—can raise a series of questions regarding aesthetics, the potential loss of historical information, and the ability to control the cleaning process adequately.
The GCI research project attempts to answer some important questions regarding the use of solvent-based gels as cleaning systems. In light of that work, Institute staff invited the heads of three Getty Museum conservation departments to sit down together to discuss some of the philosophical and technical issues related to the surface cleaning of objects in museum collections. Participating in the roundtable discussion were Brian Considine of Decorative Arts and Sculpture Conservation, Mark Leonard of Paintings Conservation, and Jerry Podany of Antiquities Conservation. Joining them in the discussion were Alberto de Tagle, chief scientist at the GCI, Narayan Khandekar, a GCI associate scientist, and Jeffrey Levin, the editor of Conservation.
Alberto de Tagle: When I first started to work on conservation-related scientific issues in the early 1980s, one of the main problems that conservators presented to me was surface cleaning. Conservators wanted to know what was really happening in the cleaning process. Since then, I've felt that this was a very important question that needed to be addressed in general terms.
At this roundtable, I'd like to talk about some of the issues of surface cleaning from the conservator's point of view. I'll start with an issue at the forefront of discussions of surface cleaning philosophies, which is that of patina—that much-prized change of the surface that comes with age. How do you define "patina," and how do you keep it when cleaning and removing the undesirable changes that occur with time?
Jerry Podany: The complexities of an archaeological artifact's surface, or its patina, have been known for some time and certainly appreciated for aesthetic beauty since antiquity. But the wealth of information contained in these alteration layers and deposits has been understood only recently, and it is more appreciated every day. Because of earlier, certainly more aggressive cleaning techniques, we've lost a great deal of that information for a lot of sculpture in collections around the world. But our field has changed considerably in the last several decades. The degree of cleaning has been reduced dramatically, and cleaning is approached with much more caution now. What survives on the surface of the object is highly valued—and that now includes the historic information offered by artificial patinas applied to ancient sculpture in the 18th and 19th centuries.
Narayan Khandekar: Jerry, the layers that you are trying to protect are not necessarily man-made or part of the creation of the object. They have accrued over a period of time.
Jerry Podany: Generally speaking, there are three categories of patina. One is an alteration layer that occurs due to accidental or natural change—during burial or weathering, for example. Another is an intentional coating, perhaps ancient or perhaps applied at a much later date as part of a restoration or later use. Finally, there are those changes or accretions that occur as indirect results of other intentional actions—rust stains from metal attachments, or obscuring stains from restoration materials that proved unstable over time. It can be quite complex and rather subjective to determine which of these categories have value, alone or in combination with others.
Narayan Khandekar: The idea of patina in the paintings field begins with the assumption that something from the underlying paint layers has penetrated into the varnish, changing the appearance of the top layer. Does that idea of patina carry across to decorative arts as well?
Brian Considine: Very definitely. The structure of the surfaces we deal with doesn't differ significantly from paintings in many cases. Whether they are oil paint layers or different types of coloring agents suspended in a binder, it's really the same type of system. But there are also some major differences. Terracotta surfaces, for example, can be very difficult to clean because of their porosity and because many have an original surface slip that is very lean in binder.
Jerry Podany: I'd like to ask Mark to comment on controversies in the cleaning of paintings. Some controversies that have erupted around sculpture ultimately have been quite healthy for our field—the recent controversy regarding the overcleaning of some of the Parthenon sculptures in the British Museum, for example, or the severe criticism of restorers and conservators by Professor Beck with respect to the justification of cleaning a number of sculptures. These criticisms from outside the field have, I think, encouraged us to look more closely at our own motivations and reasoning. Everyone—conservator, scholar, art historian, connoisseur, director, curator—is investigating more carefully why we undertake restoration and if those reasons remain valid. These controversies have had an enormous effect on sculpture conservation—and I think a positive one. What about paintings conservation?
Mark Leonard: Everything we do in conservation is geared to be reversible, but the one thing that is irreversible is cleaning. So it is the most critical conservation activity. Anything that makes us question what we are doing and why we are doing it drives our field to have a deeper understanding of the materials that we are working with. It is a good thing, even if the process is painful and annoying.
Narayan Khandekar: I have a slightly jaundiced view of cleaning controversies as related to paintings. I think they're inevitable. They have forced conservators to look at their craft, but I'm not sure how much they've directly advanced the cleaning of paintings. I don't know if they've had any other outcome except that of prompting certain outspoken members of the viewing public—who appreciate a painting in a certain state—to say that they don't like the change.
Brian Considine: I have to disagree. I support Mark and Jerry's point of view that any controversy really causes us to question what we are doing and why we are doing it. I don't think we can ever do too much of that. In my department, for example, I sometimes play devil's advocate when we are talking about a treatment, because there is tremendous benefit in really having to articulate your reasons for decisions regarding a treatment.
Mark Leonard: I think we are getting better at dealing with controversies and with the specific issues in a more intelligent fashion. I'm thinking specifically about the collaborative restoration project we have with the Yale University Art Gallery on early Italian paintings, and the work that Narayan has done to identify some original surface coatings that have miraculously survived in a few cases. It has given us a much stronger foundation upon which to address issues of our own cleaning and polemics in the past. I hope that kind of thing will increase. We're still at the frontier of understanding the issues of original surfaces in paintings, but I think we are very far along in valuing those materials. That wasn't true 25 years ago.
Brian Considine: I have to say that one of the last bastions where we see an awful lot of damage—and it's really heartbreaking—is decorative arts in the marketplace. Furniture, in particular, is automatically stripped, and mounts are regilded. It's completely aesthetically driven; there is some kind of agreement in the marketplace about how a very fine piece of 18th-century French furniture should look, and any sacrifice is made to make the object look that way. It's common practice for marquetry to be embellished by adding detail that was not originally there; for Boulle marquetry to be re-engraved; and for painted objects to be stripped and gilded instead of painted, because they are worth more in that condition.
Jerry Podany: The desire for a perfect object—and the existence of restorers who will provide one—has caused damage to antiquities for centuries. I've seen really wonderful objects ruined for the sake of a brightly polished surface or a pristine form. But the problems aren't isolated to the fashions of the market. We have our own museum fashions affecting conservation and the objects. There are many large collections of Greek and Roman objects that have had little maintenance or treatment in many years and that are now, suddenly, getting a great deal of attention. To be on the "cutting edge of conservation, some museums are subjecting their collections to fairly severe cleaning campaigns, often removing earlier restorations with little consideration of the value of what is being removed. As a result, we're losing a lot of historically important information about the attitudes of the last 300 years and about the history of restoration.
Jeffrey Levin: Mark, would you say that the paintings market is farther along in this regard?
Mark Leonard: I think a little. Fifteen years ago, we rarely saw potential acquisitions that hadn't been cleaned, but we were quite vocal about saying that we wanted to be shown pictures that had not been touched. The Getty certainly wasn't the beacon in the field—this was true for most museums. Now I rarely see a picture that has been touched. They are usually left alone, and the same is true of pictures sold at Sotheby's and Christie's. I think that once it gets into the broader market, the more expensive the picture, the better chance it has of finding its way to a good conservator and receiving proper care. On the less expensive side, things that are kind of cranked through take on a very different look and a very different treatment in that process. There is a lot of room for improvement, but I think we have come a long way.
Alberto de Tagle: One problem is that we don't have a clear definition of cleaning.
Narayan Khandekar: In the late 1980s, Gerry Hedley defined three levels of cleaning for paintings: partial, complete, and selective. Do you think the field has moved on from that?
Mark Leonard: Yes, we have moved beyond that a bit. In this country at least, I think there is a general consensus about aesthetic considerations and degrees of cleaning, and certainly a deeper understanding about what we are cleaning away, as well as the materials that we are using to do it.
I worry, however, that the pendulum is swinging just a bit too far. The more we begin to understand the value of original surfaces, what can happen—and I've seen this in various museums—is that a kind of paralysis sets in, where you become so terrified of doing anything that you wind up doing nothing. That may be good in the short run, and generally no harm comes from doing nothing, but I hope that as a field we are beginning to find a certain balance between doing nothing and doing something.
Brian Considine: I'd like to follow up on Mark's comment about the pendulum swinging. At the risk of sounding like the enfant terrible, I think there is a lot of talk about removing an original surface. If you take furniture as a case in point, sometimes there are very good reasons to remove an original finish. These are resin coatings that have a certain life span, and if a table has been subjected to light for 200 years and the finish is completely crazed and degraded, it is no longer serving its purpose. You can argue that the finish is actually obscuring the aesthetic message rather than being part of it.
Jeffrey Levin: So when you remove that surface, you are improving access to information about the object or to part of its history?
Brian Considine: Yes.
Jeffrey Levin: That's a choice you make.
Brian Considine: I'm not saying I would always make it, but it is something to consider.
Alberto de Tagle: Brian, I think you are saying that it depends on the kind of object, the type of collection, and the message you are seeking. Would the approach be the same for an archaeological object from antiquity?
Jerry Podany: It's different for ancient works. Anything that remains as part of the original surface is valued as irreplaceable. The problem is identifying what may be evidence of an ancient decorative or use-related coating or surface. The effort to do that and the results have significant implications in our cleaning decisions.
Brian Considine: The point is also that here at the Getty, we are in an incredibly privileged situation. The majority of people working on furniture have no access to a microscope.
Jerry Podany: I think you're getting to a very important complexity that we should recognize when we talk about what is and is not cleaned away. For example, let's consider ancient bronzes—and only Roman bronzes. Depending on whether that bronze is in an archaeological museum, an anthropological museum, a study collection, or a fine arts museum, it may well look entirely different because the cleaning approach taken was a direct result of the philosophy and assumptions of that particular type of institution. If you then compare a Roman bronze and a Chinese bronze in the same institution, the two objects are often treated completely differently. Somehow it's okay to remove what is still termed the "vile patina on a Roman bronze, reducing the surface to a smooth and shiny facade that is completely foreign to the corrosion and centuries it has experienced. But that type of treatment is rarely carried out on Asian bronzes, because of some romantic idea associated with the exotic and the assumed philosophical appreciation of natural processes. While there may be some truth in this, it is mostly a contradiction and an ill-founded practice. While I agree with Mark and Brian that it varies object by object, I also think we have yet to identify these contradictions within types of collections and institutions that directly affect the object.
Brian Considine: Consider how you treat terracotta in the Antiquities Department and how we treat terracottas. It's totally different.
Jerry Podany: Yes, you're right. But in this case there is a great difference in what we can assume about the original appearance of the object. We have so little direct information about antiquities, whereas the closer one gets in time and culture to an object, the more readily one understands its original intent and form.
Brian Considine: I guess I'm referring to the difference in the aesthetic standards for restoration and those for archaeological treatments. We would not repair a loss in a terracotta vase with a plain fill that was very noticeable.
Mark Leonard: I'd like to return to the issue of "patina," which is a word I don't use in paintings conservation, and one that paintings conservators as a whole seldom use. There's an important distinction. I do talk about the original skin of the picture but patina implies something more complex, and I think it is more suited to three-dimensional works of art.
As a paintings conservator, I don't think I could return an old picture to what the artist's original intent was. The materials themselves have changed so dramatically over time, and I can never turn the clock back to make it look the way it did when it left the artist's studio. All I can do is work with the changed materials, make some sense of them, and let them speak in some meaningful way. And when I find a painting that we think still has its original "skin" or surface coating, I work within the parameters of that existing surface—but I accept the vast changes that have taken place underneath that skin. The pigments have faded in some areas, but not in others. Some areas have become transparent and dull. Other areas have retained their original intensity. That complete shift in balance is what I'm playing with in the cleaning process.
Jeffrey Levin: One of the general impressions I'm getting is that as conservation has matured, and as it attracts more public attention, in an ironic way there appears to be at least the beginning of a shift toward less treatment. Conservation seems to have become as much an intellectual and philosophical activity—in terms of evaluating what you're not going to do, as opposed to what you may do. Is that correct?
Mark Leonard: It is certainly true in the general sense. But there is still a lot to be done. I hope we are far more thoughtful about why we're doing what we're doing—and slower in actually doing it. It's not unusual for us to have a new acquisition sit in the studio for two to three months before we do anything, just because it takes that much time to get to know the object.
Jeffrey Levin: Is it correct to say that 25 years ago some of the questions you are raising now would not even have been raised?
Jerry Podany: Some of the questions were raised 25 years ago, but they just hadn't filtered their way throughout the field. Change in conservation takes a long time. Whether that change is for the better or worse, it's good to move slowly. We are much more deliberate today in what we do. We spend a lot more time in introspection, because of past lessons and because our responsibilities are broader than they used to be. The more we find out about the potential impact of what we are doing, the more responsibility it carries with it. It doesn't mean that we freeze in our tracks. It just slows us down, and we act more responsibly.
So in some ways you're right. But to interpret that as meaning that our whole job is philosophical—no, as Mark said, there's plenty to do. The implications of the ethical and philosophical issues that have been brought to bear on what we do are that now nothing is done as a matter of course anymore. Now we look more carefully at each individual case.
Jeffrey Levin: And the other thing is that in some sense it may take longer to do less.
Brian Considine: Absolutely. I also feel that one of the most exciting aspects of conservation now is trying to contribute to the history of art through technical studies of the objects, the materials, and the manufacturing processes, the processes of alteration, and the accumulation of subsequent surface coatings or grime.
Jeffrey Levin: How new is this concept of conserving the surface because it provides information?
Jerry Podany: I think it differs from field to field. You can find very early examples. The first reference to the beauty of white marble is in the medieval period. By the 18th century, they were stripping everything in sight to reveal that beauty at the expense of seeing evidence for polychromy. But even then there were those who warned about the loss. It's an ongoing debate. The scale keeps tipping. Right now, conservators are tipping toward caution and toward avoiding mistakes.
Mark Leonard: One thing that comes up over and over again in cleaning controversies is scientific objectivity. I think a lot of conservation in the past was done in the name of scientific objectivity, when in fact, what we were really doing was absolving ourselves of any responsibility. I think, as a field, we understand that now—perhaps more so than 30 years ago.
Brian Considine: I think there used to be this concept that you could do something to a work of art and avoid a personal aesthetic judgment. I strongly believe that is not possible. Even the decision to do something is based on aesthetics in many cases. Even the lightest cleaning, dusting, or vacuuming involves an aesthetic intervention.
Mark Leonard: Anything you do that changes the look of the work of art changes the meaning. That can be from the simplest intervention, as Brian described, to a more radical policy.
Brian Considine: It's a personal aesthetic judgment that you're making. It can't be impersonalized.
Alberto de Tagle: Can we talk about the process by which decisions are made as to what should or should not be cleaned? Are there differences in each of your departments in how those determinations are made?
Brian Considine: I would start off by saying that there are at least two reasons to clean something. Certainly the most pressing one would be if there was the conviction that a coating was actually detrimental to the object. That obviously would carry some urgency. The other reason is the more obvious one—for an aesthetic change. In that case, we would discuss with the curator the fact that an object's current appearance was a very inaccurate representation of the artist's intent—that the viewer was being distracted by the dirt or that it was really falsifying the aesthetic message of the object. That's more of an optional intervention. In those cases, the conservators take the lead by researching the material aspects of the object, learning as much about the artist's work from the curator, and gathering information about comparable materials. We would also possibly research comparable treatments, either within the department or further afield. We would work with a conservation scientist to analyze cross sections or carry out different material analyses of the layers in question, and investigate to see if there is a cleaning system that would enable us to achieve our aesthetic goals. It's really a three-cornered collaboration that involves a lot of exchange of opinions and information.
Jerry Podany: In the antiquities field, the amount of information that we now know has been or is still lost through inappropriate cleaning—ranging from traces of pigment and decorative coatings all the way to whatever remnant of binder might still be there—is very sobering to the field. Conservators of artifacts and ethnographic material are intensely aware of the kind of damage and loss that can occur. At the Getty Museum several decades ago, curators held enormous sway over what was cleaned and how extensively it was cleaned. The conservator has always made the decision if whatever was being removed was dangerous to the object, as Brian mentioned. But if it wasn't a direct threat, then it was almost always an aesthetic decision made by the curator. That has changed significantly.
We now realize how valuable some of these deposits can be. Even if we're trying to target grime that has very little, if any, value, the action of cleaning may result in the loss of evidence that is there from antiquity or from some other cultural or historical context. For example, now there is always a very long waiting period before we begin to clean. The object may go on exhibition for a long time before we undertake cleaning. It gives us time to consider the action and the potential results. I would say that over the last 20 years, a great number of the objects that were targeted for cleaning didn't get cleaned because, over time, discussions brought to light the fact that there was no benefit in cleaning them, that removing the encrustation or some disfiguring dirt would not really benefit the object.
Then we have those cases where cleaning is simply not possible technically, at least at this moment. We have a number of objects that we know have brilliant painted designs underneath the encrustation, but the pigment is more tenaciously attached to the encrustation than to the terracotta, and so they're left alone for now. Your question is a good one, and I think our field is changing dramatically.
Brian Considine: Part of the reason that it has changed here is because of our administrative setup, where we have equal access to the director. In many museums, the conservators report directly to the curators, so they can have difficulty in not following the curator's instructions. In some European countries, the situation is more difficult because much of the conservation of museum objects is done by freelance conservators who, in an ethical disagreement, possibly face alienating themselves from future work at that institution.
Mark Leonard: I think it's a little different in paintings conservation. Let me backtrack a bit to answer your question as to how we go about deciding on whether to clean a painting. At the Getty, we do operate in an ideal world with regard to our relationship to the administration and to the curatorial departments, and in our influence over the care and appearance of the collection. In all respects, I use as my underlying philosophy, "let the work of art be your guide." So the painting is, in fact, the source for determining what needs to be done to it. That works very well when you have a knowledgeable group of conservators, curators, and conservation scientists who can all talk to one another in a common language and with a common purpose.
I think the field has matured to the point where conservators really do play as vital a role as curators in the life of the museum, and we can play an increasingly public role by being involved in exhibitions and by helping the public understand what materials these objects are made from and what has happened to them.
Alberto de Tagle: In the last 10 years, we've seen significant changes in the technical aspects of surface cleaning. Besides lasers, one of the most controversial cleaning techniques has been the gel systems—often referred to as the Wolbers methods. Can you talk about how these methods have contributed to surface cleaning approaches?
Mark Leonard: I'll start with what was a kind of epiphany for me, which is a slide that Richard Wolbers showed during his first lecture as a Getty Museum Guest Conservator in 1986. It was a cross section of a layer of shellac from a piece of furniture that had been French-polished. The shellac had been applied with repeated rubbing as part of the manual application. The cross section showed that the natural oil in the wood had been drawn up into the French polish layer.
In that single shot, Richard captured what many paintings conservators had been talking about for many years—the idea that the intimacy of the bond between the varnish coating and the oil paint underneath is much more complex than we have been able to quantify. Richard took some very important steps toward quantifying the intimacy of those bonds and was able to begin thinking about putting solvents into gel form to specifically target the kinds of surface coatings that he was able to identify.
Jeffrey Levin: Mark, that epiphany—that recognition of the complex relationship of layers of material—is it something that is now generally shared in the field?
Mark Leonard: I think it's increasingly understood. I wouldn't say that it's shared as much as it should be. There's an intuition on the part of many conservators that cleaning is not simply a matter of removing a surface coating from a substrate. It would be very simple to think of removing a varnish from a painting as an on-or-off proposition. But in fact, the relationship between the varnish and the paint goes across infinite shades of gray. You never reach a point where the varnish is all off and only the paint film remains. The bond that you're dealing with is so intimate—as was demonstrated by the slide of that French-polished cross section. The area where the oil extruded into the varnish and the varnish penetrated into the wood is this very gray region that I don't think we completely understand. Richard Wolbers provided a more scientific foundation for that intuitive concept that has been refined with the work that the Getty research team and others elsewhere are doing. But we have a long way to go.