From floods all the way to professorship: Michal Ďurovič on the preservation of monuments and the Prague Astronomical Clock’s Calendar Plate

Your 2002 book entitled Restoration and Conservation of Archival Materials and Books is considered to be a key resource in the field of written heritage conservation. What major changes and advances have you observed in this field since you first published it?

It has been 23 years since my colleagues and I wrote the book, so a lot has changed, of course. I am even currently considering preparing a second, expanded revised edition. Since then, we have made a lot of progress, for example, in the conservation of photographic materials. Back in 2002, this field was only starting to be explored in the Czech Republic and Slovakia. Another example is the restoration of wax seals, a topic addressed at UCT Prague through several Master theses and even one doctoral thesis. Since 2002, we have improved in various areas and explored them more deeply. Therefore, some chapters would need to be revised or supplemented with new scholarship.

What are the main differences in restoration approaches today compared to 2002?

I will talk about conservation and restoration in the context of archival and library collections. Things are quite different, because in the 1980s and 1990s, we used to perform a relatively invasive intervention in preserving written monuments, whereas today we approach restoration by trying to minimize contact with objects as we try to stabilize their condition. I will give an example from the past. When I started in the 1980s, it was a common practice to flatten out the parchment documents which, in the past, used to be folded prior to being stored. They had to be perfectly flattened out until, in some cases, they ended up looking as stiff as boards. Today, we approach things differently. We only flatten out folds and deformations that damage a document or prevent text from being read, simply leaving the rest “as is”. It’s similar for wax seals, which are an essential component of parchment documents. Previously, if a larger part of a seal was missing, the entire so-called “seal bowl” had to be refilled and reconstructed with new wax. Today, for example, when a damaged edge of a seal needs to be repaired, we simply fix it with a wax mixture so that the damage does not spread further. We don’t make any major additions to the shape. So, first and foremost, it is about stabilizing the object while approaching it very sensitively and making as few interventions as possible. And, when possible, making interventions removable.

How would you appraise the current state of restoration education in the Czech Republic?

There has been a big leap forward since the 1990s. When I started, the only vocational school for paper restorers was the Secondary Industrial School of Graphic Arts in Prague(today’s Václav Gollár High School of Art). It is still around and has been educating excellent and very skilled restorers to this day. In 1974, Professor Zelinger started the study of restoration at UCT Prague, but at the beginning, he only taught laboratory technologists. The professional restoration program was only accredited in 2004; since then, we have been educating restorers as well as laboratory technologists at UCT Prague. There is a similar program at Masaryk University, and I must not forget, of course, the Faculty of Restoration at the University of Pardubice. There is also a number of post-secondary vocational schools where one can study the restoration of various materials. So education in this field is broadly available, perhaps too much so.

Your graduates are now working in leading cultural institutions. What do you think ideal restoration education in the 21st century should look like? How much should chemistry be emphasized versus art?

If the process of preserving and restoring a monument is to be of any use, three professions must always come together: a lab technologist/chemist representing the natural sciences, a restorer (of course), and a humanities-educated expert (a librarian, archivist, or art historian). This rule that must be reflected in the study programs, whether for monument care technologists or practicing restorers. At UCT Prague, we follow this rule and I think that our study programs show this.

So, education from these three professions must intersect so that everyone understands each other.

Exactly. They have to be able to communicate with and understand each other. So a natural scientist, a chemist, and a lab tech must be familiar with art history and have an overview of the humanities, must understand ​​what restoration is, and also know artistic craft processes. Of course, the same applies to a restorer or an art historian/archivist/librarian as well, only in the opposite direction.

Where do you think restoration/preservation is heading? Are digitization and artificial intelligence (AI) already influencing your field?

You’re speaking to someone who isn’t exactly a big fan of digitization. It’s a bit of a problem. Of course, I have nothing against digitization technologies. I just see in cultural institutions like archives and libraries that the focus is often on digitizing objects, which is absolutely fine. Information becomes more accessible to the general public and objects themselves are also protected.

On the other hand, there will always be a shortage of funding. Less and less money is leftover for restoration itself and preservation of the physical objects. I think this is not the right approach for the long term. It would be better to balance both digitization and preservation, but that is not happening yet. I am quite concerned about it for the future. Of course, it always depends on a specific institution and its management, but the trend is clear. Because I have being doing this since 1983, I see that the emphasis nowadays is placed only and exclusively on digitization. The advent of new technologies is simply starting to undermine physical restoration as such. It is a shame. Ideally, one would balance the ratio and use new technologies only when it is really suitable. For example, using 3D printing to fill in missing parts of sculptures or ceramic/glass vessels.

Your specialization includes materials such as paper, leather, and parchment. Which of these materials do you consider the most challenging to restore? Why?

I can’t say this with absolute certainty, but I think that the most demanding materials are parchments, or rather, parchment documents. Parchment is extremely sensitive to changes in relative humidity, which subsequently causes dimensional changes. If we imagine, for example, the case of medieval manuscripts, when there is some illumination or initialization on a parchment, then the dimensional changes of the substrate/parchment often cause the coloured layer of the particular illuminated part to react differently to the dimensional changes of the whole parchment, leading to cracks (so-called “crackle”) with the coloured layer or a section detaching itself from the parchment surface. To repair this, we have to restore, or rather fix, the coloured layer to the substrate. But other materials are definitely sensitive as well. Among the great challenges are, for example, materials produced by various historical photographic techniques or archival materials from recent times.

Can you share an interesting or unusual case from your work that particularly intrigued/challenged you?

There have been many challenges in the many years I have been working, but the greatest challenges resulted from the 2002 floods. It’s unforgettable.  I’m referring only to the huge amount of damaged contemporary and historical materials. I definitely consider it a great success that so much was saved. After documents were removed from the mud, rinsed with water, and initially indexed/described, they had to be frozen quickly. Then, after some time had passed, subsequently thawed, disinfected, and, many of them, restored (some objects are still being restored today). And I am talking about almost 2,000 m3 of ice cubes in which archival materials and books were “isolated”. Over four years, 2004-2008, the documents were dried, disinfected, and thus saved.

What I noticed and appreciated at the time was that the government and its respective ministries took ownership of the rescue of documents. There was enormous support and effort dedicated to resolving the situation. Promises made and at least the majority of them were kept, which pleasantly surprised me at the time.

Was it your team that saved all of this?

In 2002, I was employed at the National Archives. Together with colleagues from the National Library, we worked very intensively on the rescue of archival materials and books. In fact, we prepared a proposal for a technology to delicately thaw and dry freeze documents (vacuum freezing using lyophilization), followed by disinfection in the ethylene oxide chambers at the National Archives, and then restoration itself. It is true that we already had some experience from the Moravian floods in 1997, which we also used last year during the floods in northern Moravia.

CT Prague’s Scientific Board has already approved the proposal for your appointment as full professor. Congratulations! Your professorship is in the field of materials engineering. What specifically do you think this new title symbolizes for the field of restoration? Does it shift your work more towards research for the commercial sector, or will you remain faithful to cultural monument restoration/preservation?

Thank you for your congratulations. In any case, I remain loyal to cultural monument preservation/restoration and related materials research. This is my life. Personally, I believe that this appointment is important for our field. As I have already said, Professor Zelinger started teaching of the conservation-restoration of monuments at UCT Prague in 1974 and lab techs for monument care were educated under him (I am a graduate of his program, by the way). Since 2004, we have also had a professional restoration study program. Gradually, we built Bachelor, Master, and Doctoral programs. I see my professorship as the next phase in our long-term emancipatory efforts.

How have developments in materials engineering and materials research been incorporated into everyday restoration practice?

If you want to restore something, you need to have proven methods and stable materials at hand. That is why materials engineering and materials research play an integral role. For example, before a restorer actually uses a specific adhesive on an original object, the substance must undergo a series of studies and tests, and only then can it be said if it can (or cannot) be used in restoring an original.

There are many examples of why this is necessary. One is very telling. In the 1950s, a restorer used the substance beta-naphthol to disinfect parchment documents in the Archives of the Crown of Bohemia. He blindly adopted the procedure and did not test the substance and its effect on parchment at all. He set about disinfecting the documents, and managed to disinfect approximately two thousand of them before discovering that the documents had started to change colour. Since it was part of the crown jewel archives, it was an incredible mess. On the other hand, it became evident from this accident that without natural sciences and thorough materials research, it really would not be possible to care for important cultural objects.

You have patented new technologies for restoration. One of your patents is a device for drying books as well as similar paper-based materials. What makes this technology unique?

During the 2002 floods, people were looking for ways to dry ice cubes and frozen paper. It was a collaboration with the Institute of Chemical Process Fundamentals of the Czech Academy of Sciences (CAS) and it involved microwave drying. Microwave radiation can overheat or burn the centre of paper blocks during drying. The proposed technology homogenized the microwave field using special ceramic tiles, thus preventing local overheating or burning of dried paper. However, after 2004, when the drying of frozen archival materials began, this method was not used. A vacuum freezing method was chosen, one that was more sensitive to dried materials and, above all, allowed for drying a much larger quantity in one batch.

Would you like to highlight any other interesting patents or technologies you’ve developed?

Several years ago, we worked on a security research project for the Czech Ministry of the Interior called Advanced Identification Element for Recognizing Archival Documents. For this, we collaborated with the Faculty of Chemistry at the Brno University of Technology, the Institute of Chemical Processes of the CAS, the Centre for Organic Chemistry Pardubice (COC), and the Czech National Archives. The goal was to design an invisible (undetectable) method of marking archival materials that would enable them to be safely identified in the event of theft and subsequent investigation/recovery. In the past, many valuable archival objects were stolen; many of them appeared at various auctions abroad or in antiquity shops after some time. The archives had to prove that they were the rightful owners. So after several years of research, we filed a patent on how to invisibly mark documents and how to subsequently identify them using X-ray fluorescence.

In 2006, you took a part in training Iraqi restorers and were helping them with establishing a restoration centre in Baghdad. What experiences did you take away from this work and what comparisons to the Czech situation would you make?

Above all, I gained great respect for the people we trained. They were employees of the Iraq National Library and Archive in Baghdad that had been seriously damaged by war in 2003.

In 2006, we were not allowed to go to Baghdad for security reasons, so the training itself took place at Salahaddin University in Erbil. Under auspices of the Czech government, we provided the Iraqi side with a restoration lab with full equipment and all materials. Everything was transported from the Czech Republic to Erbil by truck, put into operation, and then selected employees from Baghdad were trained on the premises. Training also included a follow-up course in the restoration of paper documents and books. I say “follow-up” because these employees were first trained in Prague in 2004 and then in Florence in 2005. During the courses in Prague and Erbil, very personal and friendly ties were formed between participating parties. In Baghdad, but generally throughout Iraq, the situation was a very turbulent and our Iraqi “students” did not know anything about what was happening to their loved ones back home. It must have been very psychologically demanding and stressful for them, yet they still were determined to learn. They were hardworking, modest, inquisitive, and engaged in discussions. After the courses were over, the lab was dismantled and transported to its final destination in Baghdad, but we were no longer there.

In recent years, the restoration of the Mánes’ calendar plate, part of the Prague Astronomical Clock, has sparked much debate. How do you view this case from the perspective of a restoration expert, and where do you think the line lies between faithful restoration and creative reinterpretation? Should a restorer be more of a conservator or an artist?

In my opinion, a restorer must put all of their knowledge, skill, and abilities to the benefit of the work being restored. One cannot be an artist in the sense of free creation or reinterpretation of the original. A restorer must be able of empathizing with the creator of the restored object to the fullest extent possible. One simply must suppress one’s ego. The case regarding the unsuccessful copy of Mánes’ calendar plate at the Old Town Hall has been in the news. In my opinion, the contracting authority failed to control the situation. UCT Prague is currently cooperating with the Academy of Fine Arts in Prague to make a new copy of the calendar faithful to the original. However, even this new copy does not have to be identical (in terms of materials and technology) to the original. After all, Mánes had made some mistakes on the original plate himself. He was clearly in a hurry and the substrate had not matured sufficiently, so cracks appeared on the original painting very soon after the plate was installed, back in 1866.

We are currently engaged in the selection of suitable (stable) pigments, binders, varnishes, and UV absorbers. The work is placed on the southern side of the Old Town Hall, which is very exposed to sunlight as well as weather changes. The result of our work will be the design of the entire process, from the underlying copper plate itself (it has a diameter of three meters) to its surface treatment and the selection of suitable pigments and varnishes with ultraviolet absorbers. After this, colleagues from the Academy of Fine Arts will paint a faithful copy. No experiments and improvisations will be allowed this time.

Who should decide about what form important cultural objects should take?

As in the case I already mentioned, the three stakeholder professions should come together to form an appropriate plan. Just one expert or one profession should make decisions on their own.

What are you currently working on?

We have recently gotten involved in an interesting security research project for the Ministry of the Interior, which I am really happy about. We are working on development of a new,  the state-of-the-art fireproof wrapping for so-called “archive boxes” used for long-term storage and protection of archival materials. We have managed to find a suitable flame retardant that will be applied to the surface of these archive boxes.

Of course, the retardant must be thoroughly studied and tested. Not only its effectiveness, but also its long-term effect on the physical and chemical properties of the cardboard from which the wrapping is made. We are cooperating with the Faculty of Chemistry at the Brno Technical University, the Technical Institute of Fire Protection in Prague (TUPO), and the manufacturer of the newly developed wrapping (EMBA Paseky nad Jizerou) for this task. We would like to eventually create a resultant commercial product.

Can you tell me what kind of substance we’re talking about and how it is applied?

It is essentially a layer of bentonite with a suitable binder. This layer protects the archival materials stored in the archive box with a barrier effect. The retardant is applied using a special technique that we’re currently deciding upon. So far, it looks like we are moving towards using screen printing, but there are still some problems to be figured out. In 2022, we conducted a medium-scale fire test with TUPO. It was a fairly large fire and the designed retardant was highly effective and withstood the test. It perfectly protected both the archive boxes as well as the archival materials stored in them.

If you had a dream object to restore, what would it be?

I can’t say that I have any wish to restore a particular archival object, document, manuscript. During my professional career, I have had the opportunity to be involved in the restoration of a number of truly significant Czech books and archival materials. Just to name a few, I would mention the documents of the Archives of the Crown of Bohemia, the Vyšehrad Codex, the Litoměřice Gradual of 1517, the Zbraslav Chronicle, the Gelnhausen Codex, the Broumov Land Registry, the Altman’s Panorama, and many, many others. However, what would make me immensely happy as a chemist is to solve a problem that has persisted for more than a century, which is the decay of manuscripts written with iron gall inks. Libraries and archives store a huge number of manuscripts written with these inks (they were used from ancient Rome until the mid-19th century). And these manuscripts, whether written on handmade paper or parchment, decay for two reasons. Iron gall ink is extremely acidic, so it irreversibly hydrolytically damages paper as well as the much more durable parchment substrate. Also, it contains not only ferric/ferrous ions from greenstone, but often also copper or zinc ions. These are effective catalysts for the acid hydrolysis of glycosidic or peptide bonds, but they also significantly accelerate the oxidation of these materials. We have managed to cope with acid hydrolysis, but we have not yet satisfactorily figured out how to stop, or rather slow down, the decay caused by oxidation and eliminate the catalytic effect of the aforementioned ions. If this were possible, it could save a huge number of slowly disappearing manuscripts written with this ink, in libraries and archives around the world. I have seen this problem in Iraq, Peru, in the USA, across Europe, everywhere…