Session 7 - Greener Treatments and Materials

This second part of the Session theme “Greener Treatments and Materials”, had a diverse range of materials that were examined from finding alternative adhesives for stone conservation to stabilization of archaeological iron and study on protective coatings for silver followed by Outdoor Painted Sculpture conservation. Such a gamut of materials could only promise much discussion and interesting findings!

Bettina Ebert started her talk like a narrative; an unfolding story about how she and her conservation team at Stavanger Cathedral, Norway, were restoring the medieval building, and they discovered a strange adhesive mixture that had been used for historic repair. She went on to explain how they figured out the composition of this undocumented wood tar that had been traditionally used for repairs and was holding up even centuries later. She touched upon the broader concept of using traditional techniques for sustainable restoration solutions and how such intangible skills can inform current conservation practices. A happy ending to a truly immersive presentation.

Patrycja Petrasz elaborated her study on “Green Alternatives for Archaeological Iron Stabilization”, starting with the most exciting breakthroughs in archaeological conservation. We know how conserving unstable, chloride-contaminated archaeological iron artifacts are a major challenge due to the destructive nature of traditional methods, however the Horizon Europe GoGreen project explores an exciting and sustainable solution. Patrycja explained how her team’s research uses microorganisms for iron stabilization. While microbes such as halogenophilic fungi absorb chloride ions, iron-reducing bacteria can transform unstable corrosion products into stable compounds like magnetite.

It was fascinating when the speaker introduced Meyerozyma – a fungi that not only stabilizes corrosion but also changes the surface colour of iron from orange to black—showing visual proof of transformation. Imagine seeing an ancient iron artifact go from a brittle, rusted orange to a stable, deep black, thanks to fungi! This bio-based approach is not just sustainable and less toxic, it’s also a truly fascinating blend of nature and technology helping us preserve history.

Still on the archaeological methods conservation topic, Stephanie Guidera presented her team’s “Study of Protective Coatings for Archaeological Silver”. In the present, a complex alloy composition further complicates the challenge of the typical persistent nature of corrosion in silver objects. This study by the National Museum of the American Indian (NMAI), tested modern and commonly-used protective coatings on Chimú culture silver objects.

Their testing approach was quite intriguing as instead of directly testing on the archaeological silver, they replicated it using historical techniques, to obtain authentic surface textures and composition, to apply the testing treatments. It proved to be a safe choice as the results were less than ideal – while coated artifacts appeared protected, the coatings sometimes led to corrosion in hard-to-reach areas or removed trace amounts of original silver during reapplication.

Interestingly, uncoated silver (though slightly tarnished) held up better under corrosive conditions. This discovery supports the shift towards passive methods like humidity control and corrosion-inhibiting storage materials, offering a safer, more sustainable approach to silver preservation. Overall, the study challenges traditional reliance on coatings and opens new discussions about the best practices for safeguarding archaeological silver.

The last presentation was by Ellen Moody, during which she stressed the need for training conservators, as this will go a long way in the preservation efforts. The question posed by Ellen was: how do we manage the troubling environmental issues (climate change factors)?
It is along this background that Ellen saw the need for capacity building programmes for conservators in a sustainable manner to have solutions to treating outdoor painted sculptures. She further asserted that it is paramount to have conservators trained in the preservation of sculptures in more sustainable ways for posterity, otherwise, we may end up losing our heritage as most, if not all, the sculptures represent the cultural identity of a people.

The proper and wise handling of the sculptures calls for concerted efforts, thus warranting the provision of skills for conservators to effectively and efficiently preserve the sculptures. Furthermore, the acquisition of requisite knowledge is a worthwhile venture for conservators to be trained on how to treat outdoor sculptures to ensure the longevity of both the form and colours of the sculptures. 

Q&As

Stavroula Golfomitsou (session chair) started the Q & A session with the online audience asking specific questions about efficacy of the treatments and adaptation to other materials. Several of the questions were targeted towards this end and whether collaborations could be established with other research groups. Perhaps we should create a library of tested material that could be accessed, even remotely, by conservators. 

As an online DEV, Sara noticed that a great deal of the online audience was taking time during their work hours to view and participate, revealing how important this session was to them. Indeed it was a very talkative chat with lots of positive comments as soon as a speaker finished their presentation, and many good questions, with none left unanswered. 

The online audience was particularly fond of the idea of sharing “mock ups / experimental pieces” as proposed during the Q&As. 

BLOG AUTHORS AND BYLINES: 

Sara is an MA student in Conservation and Restoration of Cultural Heritage, at Universidade Católica Portuguesa, Porto (Portugal)

Brinda Gaitonde Nayak is a conservation architect who works on World Heritage Sites in India.

Ebrima Jammeh is a Destination Manager, UNESCO World Heritage Sites Manager, Cultural Officer