Artefacts, conservation and science

Ágnes Timár-Balázsy(†)

In his monograph, "The basic principles of museology", József Korek mentions that cult and votive objects were inventoried on Crete during the 2nd millennium B.C. and that there is written evidence that they were cleaned and, also, that considerable care was taken to ensure their preservation.[1] The beginning of conservation is probably coeval with the moment that Homo sapiens began to make artefacts that had to be repaired if they became damaged.[2] In the Middle Ages great artists such as Michelangelo often restored fragments from antiquity, although their ultimate goal was not always an authentic reconstruction, since they rather used this as a medium to express their own artistic ideas. Utilitarian objects and valuables were repaired and restored by accomplished artisans. Conservators are often still regarded as little more than people with clever hands. Professionals with a scientific training began to study the problems of cleaning coins and the cleaning and conservation of the archaeological finds from Greece and other countries in the 19th century. Pottery fragments were desalinated in huge wooden tubs in which the water was constantly changed in the conservation workshop of the Royal Academy in Berlin.[3]

There was indeed need for scientific expertise since it was believed even as late as the mid-19th century that corrosion was a bacterial infection that spread similarly to a plague, hence the words bronzpestis (bronze plague) and ónpestis (tin plague) in Hungarian. Steffensen, the curator of the National Museum in Copenhagen prescribed the following 'cure' in 1867: the infected layers should be removed by heating the metal artefact until it became red and then immersing it in dilute sulphuric acid, whereby the 'sick' parts would snap off. Fortunately, he also noted that this procedure was only successful if the artefact had a metal core.[4] By the early 20th century, however, several studies had appeared discussing the chemical and electrochemical origins of metal corrosion. Friedrich Rathgen treated metal finds in a chloride removing liquid since he believed that corrosion was caused by chlorides.[5]

It is evident from this very brief overview of the history of conservation that even though it calls for creativity and manual skills, conservation is essentially an interdisciplinary science: this profession has contributed much to historical studies while, at the same time, it draws heavily from physics, chemistry and biology, and often relies on philosophy and ethics when seeking the best procedure for the conservation of an artefact. In the following I shall quote a few case studies from these fields.

The contribution of conservation to historical studies

When conservators are expected to address various issues in archaeology or historical studies, the role of the conservator is obvious. Many examples can also be quoted of how a particular problem is resolved by certain details observed by the conservator on a certain object. There is currently a lively debate on whether metal vessels and artefacts should be restored to their 'original' form. Corfield has argued that the conservator - and the museologist - must preserve or restore the artefact to the form that offers the greatest amount of cultural and historical information.[6] When Péter Horváth, a conservator working in the Kaposvár museum began working on the greaves recovered from Lengyeltóti, he consulted with the archaeologist as how they should proceed. The originally convex greaves had been flattened at the time of the burial and folded several times along the longitudinal axis, then hammered together along the folds (Fig. 1.). [The metal greaves from Lengyeltóti]. The original condition of this metal find bears witness to how it had been deposited in the grave. In this form, however, very little could be said about the decorative motifs ornamenting them or about their manufacturing technique. Therefore both the archaeologist and the conservator agreed that the greaves should be restored to their original form. The condition of the artefact was carefully documented before it was smoothed out
(Fig. 2.) [The smoothing out of the greaves]. After they were restored to their original form based on the dimensions of analogous finds, the ornamental motifs could be excellently observed and, as it turned out, these greaves were more artfully crafted that the other intact pieces in Hungarian collections (Fig. 3.) [The greaves after restoration].[7]

At the wedding of Rudolf Hapsburg in 1881 the ladies of the Czech aristocracy presented him with a masterpiece of the goldsmith's art depicting the Týn church of Prague. This masterpiece of Historicism eventually ended up in the treasury of the Benedictine abbey in Pannonhalma. Balázs Szőke chose this piece as the subject of his diploma work. Since corrosion could be noted in its interior, he began to disassemble the piece that was made up of about seventy elements. It turned out that this masterpiece of the goldsmith's art was in fact a reliquary containing the relics of four Czech saints: St. Venceslas, St. Adalbert, St. John of Nepomuck and St. Ludmilla.[8]

The collection of the National Széchényi Library includes a leather-bound German Renaissance book from 1576 that awaits conservation in an unsuitable condition. After Éva Benedek, a student from Transylvania, had carefully unpicked the binding of this book she disinfected and cleaned the fragile pages. She restored the pages using paper pulp and then proceeded to re-bind the pages using the original technique. Following the conservation of the leather binding the contents of the book can now be studied by researchers.[9]

It is known that after the crypt in the White Church of Vác was emptied in 1994, the 18-19th century coffins and their finds were taken to the Tragor Ignác Museum. Many of these finds could be dated by the date inscribed onto the coffin, but some of the finds came from the ossuary, without any clues as to their original provenance. Following the disinfecting and cleaning of the mildewed leather fragments covered with decay and greasy stains, Márta Bendefy, the chemist-conservator of the Hungarian National Museum reconstructed a pair of gaiters from the fragments. Since she did not find any analogous finds in Hungarian collections and neither could she find any description of the use of comparable footwear in contemporary sources, she began to search for parallels in Western European works, primarily in studies discussing military costume. She found the drawing of a pair of gaiters in Diderot's Encyclopaedia, since French dragoons had worn gaiters from the 17th century and gaiters were also issued to soldiers in western European armies. In contrast, gaiters were not worn in the Hungarian army since Hungarian soldiers wore simple or lace-up high boots. It thus seemed likely that the person who had originally worn these gaiters was of foreign extract. Knowing that this find came from one of the early burials, ethnologist Emil Ráduly assembled a list of the people who had been buried in the crypt between 1730 and 1789 and who had not been laid to rest in a coffin. The Hungarians, nobles and burghers could be excluded from the list of seventeen individuals. The remaining persons included one Josephus Choronfeld who had been buried on March 5, 1740 since the parish register includes the remark that he had been a military commissioner.[10] The exemplary conservation of this find was all the more important since this is the single currently known pair of this gaiters type in Hungary.

The application of physics, chemistry and biology in the study of fabrics and manufacturing techniques

The importance of physics in the discovery and application of X-rays is well known. There are few archaeologists or conservators who have not submitted an artefact for X-ray analysis. Katalin Bruder, conservator working in the Hungarian National Museum, found that the cleaning of a Conquest period strap end with silver inlay was much easier with the aid of the X-ray photo of the find made by Gábor Hutai, also a conservator in the museum, since she was able to clean the find without damaging the ornamentation.

Márta Járó, chemist (HNM) has devoted much effort to studying the manufacturing techniques of metallic threads in historical textiles to determine their structure and material. On the basis of the statistical evaluation of the scientific investigation data she has been able to identify over forty different types of metal threads made using different techniques. The morphology of the metal threads was analysed by light microscopy and scanning electron microscopy, the identification of the materials used was carried out by energy dispersive X-ray microanalysis.

The Avar cemetery of Zamárdi yielded strap ends (Fig. 4.) [Strap ends found in the Avar cemetery of Zamárdi] on which Ilona Vámos, conservator working in Kaposvár County Museum, identified corrosion and a substance of an unusual colour under the microscope. These substances were noted in the engraved pattern decorating the strap ends. Electron probe micro-analysis, X-ray diffraction and accelerated ion ray PIXE analyses revealed the presence of high amounts of copper and tin in this substance that was either green, turquoise or black, depending on the metal composition. Gas chromatography revealed a mixture of resin and wax. It became clear that the engraved patterns were filled with substances of different colour, a decorative technique known as 'Spaniarding' (Fig. 5.) [Traces of wax in the engravings - evidences for the use of "spaniarding" technique].[11]

The fragment of a statue depicting the Virgin holding the Infant came to light during the excavation of the 13th-16th century Franciscan cloister monastery in the Sándor Palace of Budapest (Fig. 6.) [Painted statue of Virgin Mary from the Buda Castle] (Fig. 7.) [Sampling spot on the statue]. Klára Török, chemist-conservator and László Kriston, physician, took small samples of the fabric and embedded them in resin and then proceeded to obtain a fine section of the fabric (Fig. 8.) [Thin section of painting layer with fluorite crystals]. They analyzed these samples not only with a microscope, but also with X-ray diffraction. They found that the pigment of the bluish-purple colour was fluorite (CaF₂) which had thus been identified for the first time on a Hungarian find since it was until then believed that this pigment only occurred on German and Austrian paintings. It now remains to be established whether this pigment had been brought to Hungary by a German or Austrian master, or whether it originates from the Velence Mts in Hungary and can thus be considered to be of local origin. These questions would not have been raised if the pigment had not been analyzed. [12]

The museologist of the Ethnographic Museum collected an unusual doll in Peru. It was agreed that this object was indeed unique. When László Torma identified the fibres - based on the microscope image - he found that the stitches depicting the eyes and the mouth were made from synthetic yarn.[13] The object was so unique that there was no other like it - the Peruvian forgers used pre-Columbian mummy shrouds for manufacturing their fakes and they misled potential buyers with this semi-authenticity (Fig. 9.) [Drawing of the Peruvian doll in the Museum of Ethnography (inv. no. 82.100.1)].[14]

A 19th century charter made of paper and parchment in the collection of the Hungarian National Archives was probably kept under humid conditions. Owing to the humidity and the enzymes of the aspergilli, the pages weakened and became brittle. The analyses carried out in the Research Institute for Plant Protection of the Hungarian Academy of Sciences revealed that a fungus of the Aspergillus species and another unicellular yeast fungus had infected the pages and that these two fungi had degraded the cellulose. After discovering the larva skins between the pages, Katalin Orosz also noted that the larvae of common museum beetles had also contributed to the damages. The biological analyses thus explained the reason for the bad condition of the charter and also contributed to determining what disinfecting procedure should be applied. Following cleaning, conservation and restoration the charter regained its original beauty.[15]

When in 1982 the workgroup studying the Hungarian coronation mantle made a scanning electron microscope photo for the examination of the fibres, the photograph revealed the presence of Aspergillus glaucus spores that would otherwise have remained undetected. After the identification of the spores it was possible to determine under what conditions the mantle should be kept to avoid the germination of these spores that would damage this important relic and to avoid chemical disinfecting.[16]

A working knowledge of biology is indispensable not only in order to recognize biological hazards and their traces. Without any botanical expertise, László Molnár, a conservator working in the Hungarian National Gallery would have been unable to identify the wood species used for the inlay of an 18th century casket in the collection of the Dobó István Museum in Eger. With the help of Károly Babos, working in the Department of Plant Taxonomy of the Eötvös Loránd University, he was able to determine from the microscopic features of the thin sectioned samples that the inlay of the fan motif was made using common birch (Betula pendula).[17]

Following any of the analyses described in the above and in knowledge of the additional information they offer, the conservator can start the treatment of the artefact. Two main types of conservation are distinguished: preventive and interventionist conservation. Preventive conservation essentially means that the object itself is not affected, and that the conservation basically ensures only a suitable environment guaranteeing the survival of the object, involving also perhaps physical support or reinforcement and a packaging preventing further damage. The temperature and humidity control equipment and the exhibition cases with a constant temperature and relative humidity level provided by silica gel of the permanent exhibitions in the Hungarian National Museum may serve as an example for other exhibitions, and the same may be said of the lighting and a number of other solutions. Márta Járó, an expert in mounting exhibitions, primarily applied physics and chemistry for determination of the appropriate parameters.[18]

The chemical process of disintegration and deterioration must also be mentioned in passing when speaking of preventive conservation and the various possibilities of this procedure. These processes are usually spontaneous and the decomposing or deteriorating substance passes from a higher to a lower energy level. This process is only triggered if there is activation energy. This activation energy is smaller in the presence of so-called catalysts. A conservator can do one of three things in order to prevent decomposition:
(a) prevention of activation energy, either in the form of light or heat, from reaching the object,
(b) removal of the catalysts from its surface: these include corroding metals, such as the copper and iron pins that are still often used to display textile and paper objects,
(c) exclusion of gases and compounds (such as oxygen, hydrogen sulphide, acidic gases, etc.) that might react with the fabric of the object and trigger decomposition or further deterioration from the direct environment of the object. This is a very expensive procedure that can be afforded in wealthy countries such as the US, where the Declaration of Independence, the Constitution of the United States and the documents of the Bill of Rights are kept in a helium atmosphere with the exclusion of oxygen. If we make use of all three options, we have indeed done everything to ensure the survival of the object.

Cleaning is one of the most delicate procedures of interventionist conservation. Cleaning is an irreversible process and it is therefore absolutely necessary to record and document everything that might be important for later studies. Parallel to the advances made in chemistry, a wide variety of cleaning procedures involving chemicals have become extensively used by conservators. The cleaning of bronze and iron artefacts in chelate solutions is a fairly common practice.[19] However, cleaning involving the use of chemical solutions calls for very careful monitoring of the process since although the conservator only strives to remove the corrosion product, there is a danger that the original metal or metal inlay might also be damaged. Many metal conservators prefer mechanical cleaning under the microscope since this ensures that he can terminate the process exactly when necessary. Cleaning with a laser beam, a procedure that is now frequently employed, has many advantages, although its application still raises many problems.

In the past ten years it has become clear that a good glass adhesive only becomes invisible in the restored glass object if its refractive index and refractional properties are identical with that of the glass object. Since, however, the refractive index largely depends on the glass object's manufacturing technique and the nature/extent of the damage, it is often difficult to find an adhesive with a suitable refractive index. The differences are visible on two Roman glasses restored under the direction of Péter Földessy and Judit Lőrinczy: one was restored quite a few years ago and the refractive index of the adhesive differs strongly from that of the glass object, while on the other, a glass object assembled from its tiny fragments, the adhesive is hardly visible.

Every archaeologist has seen how wooden finds shrink and crack if they have not been impregnated before drying. The aim of impregnation is to replace the water that fills the cell walls, the capillaries and the pores, with a substance that preserves the original form of the wooden object after drying. In the case of the Vasa, the Swedish ship, spraying with polyethylene glycol (PEG) dissolved in warm water was used in the 70-ies that filled the capillaries similarly to a plastic based wax.[20] The candle-like wax was removed from the surface with warm air. The later disadvantage of this impregnation procedure, used extensively also in Hungary, was that although the smaller PEG molecules penetrated the fabric quite deeply, they did not consolidate it well enough, while the larger PEG molecules only penetrated to a certain depth and it often happened that they formed a solid layer, while the interior of the wooden object remained without consolidation. This caused tension leading to further cracks. András Morgós, chemist-conservator (HNM), prefers impregnation with saccharides, mannitol, sorbitol or lactitol since these substances penetrate deeply owing to their smaller molecular size, they offer suitable solidity, they are fairly cheap and they do not pose a health danger.[21]

Turning now to the dangers of cleaning textiles, I shall first address the dangers of whitening. Many museologists and conservators still believe that the finds - and this is primarily true of ethnographic finds - must be presented to the public in its original pristine condition. This is true to a certain extent since a greyish tablecloth (which was originally snow-white) would be rather strange in the interior of a house in an open-air museum. At the same time, both museologists and conservators must be aware of the pitfalls of this procedure since the chemical bleachers are unable to differentiate between the substances causing discoloration and the intact fibres. While the coloured compounds are oxidized colourless, mechanical damage is caused to the fibres, in other words, the textile is weakened. The question of whether a pall from a crypt should be whitened is not only a chemical, but also an ethical question: the process of ageing undergone by a piece of textile deposited in a crypt is also part of the fabric's history.

One last example of cleaning textiles again illustrates the need for employing the results of chemical and fabric analyses: at the beginning of her career Erzsébet Vágó, a conservator working in the Museum of Military History, was asked to clean the silver braids of a military uniform that had originally belonged to a member of Maria Theresa's Hungarian Noble Bodyguard. She used a slightly alkaline solution that had been used for cleaning silver. The silver braids became clean, but the red colour of the uniform turned bluish owing to the alkaline solution. Fortunately the results of the pigment analyses were known by then: the scarlet red dye of the garment was identified as a dye gained from the cochineal insect that is extremely sensitive to an acidic/alkaline change and gives an entirely different colour in an acidic than in an alkaline environment. Although the conservator was able to restore the original colour with acidic treatment, she was unable to reverse the damage caused to the woollen fabric using the alkaline treatment.[22]

Finally I would like to discuss philosophy and ethics that, incidentally, precedes any conservation work. While twenty years ago the main goal of conservation was the restoration of the object's 'originality', a number of ethical codes and guidelines had been laid down by the 1980s and 1990s that meant greater restrictions. Conservators now have to document the present condition of the object and they also have to take greater care in decision-making. They have to consider principles according to which museologists attach much greater importance to the 'impurities' on the object, to the information that can be drawn from traces of use and wear. In other words, the main goal now is the preservation of the object's 'integrity', the preservation of traces of wear and of possible deformations owing to its use, the ultimate objective being the presentation of all aspects of the object in question. This often includes the preservation of earlier reparations: let us imagine, for example, if someone wanted to remove the soldering on the Hungarian crown which had made it suitable for the very last coronation, even though this soldering is very sloppy to say the least and can hardly be called restoration in any sense of the word. Still, it has become part of the crown's history.

In 1982, when the Hungarian Coronation Insignia Committee commissioned a group of conservators to examine the Hungarian Coronation Mantle, to determine its condition and to suggest a conservation procedure, the principle of 'minimal intervention' that is the norm today had not even been heard of. When the workgroup, headed by Katalin Nagy, chief conservator of the Museum of Applied Arts reviewed the condition of the mantle, they found the following:

(1) The mantle embroidered onto Byzantine silk in the 11th century had originally been a bell shaped chasuble from which a strip had been removed at its base and its centre when it had been transformed in the 13th century.

(2) By the early 17th century the Byzantine silk had deteriorated to such an extent that the slightly deformed mantle was sewn onto an Italian pattern-weave silk (lampasette) with rather coarse stitches.

(3) In 1848 the mantle was reinforced with another lining of claret coloured silk taffeta. This was sewn onto the preceding two layers with rather coarse stitches, too. Only the third lining, added before the coronation of Francis Joseph in 1867 had not been sewn onto the previous two, but merely fastened at the edges.

An internationally acclaimed professional conservator suggested that the different layers should be cleaned and conserved separately and then sewn together again, a procedure that was generally accepted at the time. The conservator responsible for the work, however, examined the following questions:

(1) The original bell shaped chasuble could hardly be reproduced and thus only the 13th century modified form can be regarded as the 'original'.

(2) When the damaged Byzantine silk was applied onto the Italian lampasette, this deformed condition was essentially conserved. This remained unchanged with the following, second lining. If these layers were to be separated, they would undergo a change in size and it would be practically impossible to re-assemble the mantle in its present form. These changes in size would be increased following a wet cleaning procedure.

(3) Even if only a single layer were removed and the first two were kept together, the removal of the sewing thread would entail a serious loss of material and the damaged Byzantine silk would deteriorate further.

It was finally decided that the mantle should not be disassembled and that the stitches holding the three layers together should be regarded as historical stitches even if aesthetically they leave a lot to be desired: in other words, the mantle should be preserved in its 'historical reality'. After a thorough examination it became clear that there were no stains or impurities on the mantle that would cause further deterioration and the fungus spores would not germinate under suitable temperature and humidity conditions. The Coronation Insignia Committee was presented with a conservation plan that essentially suggested that the mantle did not need restoration: only a very careful low-suction "dusting" was necessary and the deposition of the piece in a suitable showcase. This suggestion was a very revolutionary one in the early 1980s, bearing witness to a philosophical, ethical and moral attitude, with the conservator acting in the best interest of the object and its contribution to historical studies.

It is my hope that the above case studies have offered a fairly rounded picture of the contribution of restoration and conservation to the historical disciplines and of how the new advances in ion chemistry, physics and biology are applied in this profession, as well as of the philosophical and ethical dilemmas that must be faced. Conservation is an interdisciplinary activity that also calls for a sense of aesthetic beauty, creativity and a working knowledge of certain handicrafts.

I would like to thank my colleagues mentioned here who kindly allowed me to quote their works and offered many helpful comments while I was preparing this paper.