The conservation of glass is still a limited profession, with trainees coming from various disciplines into specializing with glass. Most Europeans train in a conservation program focusing on ceramics and glass, while the United States conservation programs do not have a specialization in glass, but a more general area, such as ‘objects’. Internships or traineeships provide students with an in depth study of materials and techniques that are available for glass conservation. Some of the newest advances in glass conservation have been introduced since 1993, and include the use of Paraloid B-72 as an adhesive, particularly for ancient glass collections, because it is more stable and more reversible than the traditional use of epoxy.
Loss compensation for missing areas in a broken glass continues to be one of the most challenging areas of expertise. Research into alternative materials to the standard polyester resins and epoxy resins has provided opportunities for simpler and less invasive restorations (that are also more stable). The dissemination of these new methods, materials and techniques is critical to the international glass conservation community, and conferences such as GLASSAC are essential to the spread and understanding of this knowledge.
Stained glass conservation remains a separate field. This is a result of the need for a conservator to be an artisan with significant experience in glass making, tooling, and mechanical (joinery), i.e. working with lead caming and solders. Communication continues to grow with the different fields through conferences, training courses, lectures and cross-over internships.

(by courtesy of) Stephen Koob

Glass Conservation Presentations

Stephen Koob
The Corning Museum of Glass

Conservation of glass at the CMoG: Training and future developments
The Corning Museum of Glass has become the center for training in the conservation of glass objects. For almost 20 years the museum has accepted student interns, trainees, and conservational professionals from all over the world for training. Training is offered in both theory and practice, and includes work with a variety of glass objects, from ancient to modern. Hands-on experience is given in cleaning, use of adhesives, filling losses, and preparation for exhibition.

Hanna Pohle
Conservator for glass and mosaics at workshop Gustav van Treeck, Munich

Maintenance and safeguarding of stained glass windows
Maintenance programs provide an insight into the condition of stained glass windows conserved in projects since the beginning of the widespread installation of protective glazing. In this paper two examples from the last years’ workshop practice – the stained glass windows of St. Martha, Nuremberg and St. Jakob, Straubing, both in southern Germany – are presented. The examinations reveal the performance of conservation materials and the functional capability of the protective glazing from the early 1980’s as well as around 2006. The impact of the former conservation measures to the present condition of the historic glass panels is discussed.

Teresa Palomar
Research Unit VICARTE- Glass and Ceramic for the Arts and Department of Conservation and Restoration, Campus de Caparica (FCT-UNL) 2829-516 Caparica, Portugal

Thermographic analysis of glasses, enamels and grisailles from stained glass windows
Infrared thermography is a non-destructive and contactless technique which has been applied in conservation science principally on historical buildings and structures, however the studies on glassy materials are scarce. In this study, the thermographic assessment of glasses, enamels and grisailles from stained glass windows has been carried out.

Edyta Bernady
Jan Matejko Academy of Fine Arts in Kraków, Faculty of Conservation and Restoration of Works of Art

Final results of analysis of a 15th c. stained-glass panel "The Throne of Grace" from the Dominican Monastery in Kraków, Poland
The conservation of the stained-glass panel depicting “The Throne of Grace” allowed a deep study of an exceptional example of Polish medieval stained-glass art. The goal was an analysis of the composition of glass, vitreous paints and corrosion crust, as well as the morphology of deteriorated layers of glass and paint layers. Instrumental techniques such as MA-XRF, SEM imaging, SEM-EDS and XRPD were applied. MA-XRF allowed a non-invasive preliminary analysis of glass and paint. The received data, collectively with SEM-EDS analysis of glass cross-sections, provided information on the technology and condition of the panel. The study was complemented with XRPD technique, which allowed the identification of the weathering products. Final conclusions contributed to a better understanding of the technology and the deterioration processes affecting the panel, thereby led to the compilation of a treatment proposal.

Loryelle Sessegolo
LISA UMR 7583 CNRS / UPEC / UPD, 61 avenue du Général de Gaulle 94010 Créteil, France

Surface roughness impact on medieval stained glass alteration
The aim of this study is to evaluate the influence of the initial roughness of a glass on its alteration and to determine the evolution of the roughness over time. For this purpose, alteration experiments of two glass samples, one polished and the other one highly rough, were carried out. The results show that the initial glass roughness has a strong impact on the alteration. If the glass has an initial smooth surface, the alteration layer will be constituted by different sublayers which will tend to scale as the alteration progresses. If the initial glass surface is very rough, the alteration will begin by digging the asperities and then homogenize, which decreases the roughness.

Rania Kordali
Laboratory of Archaeometry, Department of History, Archaeology and Cultural Resources Management, University of the Peloponnese, 24133, Kalamata, Greece

Corrosion patterns of a historical glass collection from Greece
The corrosion mechanisms of ancient glasses are a complex process (Zacharias & Palamara, 2016). The objects which have been exposed to the burial environments, usually lack coherency and transparency. The examination of excavated corroded glasses, often concludes to alkalis loss and the formation of different corrosion patterns on the surface. In this study a collection of soda lime silica glasses is examined, aiming to the characterization and classification of their corrosion patterns. The under study samples originated from the mainland Greece, Thebes.
In the present study a combination of analytical techniques, mainly non-destructive, namely LED optical microscopy (LED-OM), Scanning Electron Microscopy coupled with an Energy Dispersive Spectrometer (SEM-EDS), and Rutherford Backscattering Spectroscopy (RBS), were used to completely fingerprint the corrosion mechanisms. The analytical data provided useful information about their preservation state and the observed corrosion patterns.

Glass Conservation Posters

Fanny Alloteau
Chimie ParisTech, PSL Research University, CNRS, Institut de Recherche de Chimie Paris (IRCP), F-75005 Paris, France

Research of a chemical treatment based on zinc salts for ancient glass objects sensible to atmospheric degradation in museums
Zinc salts are known to have a positive effect on silicate glass surfaces against atmospheric alteration but the scientific bases are lacking to explain this effect. In this study we evaluate the potentiality of a treatment based on zinc salts to protect ancient glass objects from atmospheric degradation. In the meantime the mechanisms of the atmospheric alteration and the origin of the protection are investigated. To this purpose, glass replicas are aged in climatic chamber and altered layers are characterized with complementary tools (mainly SEM-EDX, Raman, NMR, SIMS). A positive effect of Zn(II) to reduce the replica glass hydrated thickness is confirmed and hypothesis are drawn to explain the results.

Caitlyn Phipps
School of the Built Environment, Heriot-Watt University, Edinburgh UK

Protecting historic window glass in Scotland. A look at the planning application approval rates over a 10 year period.
Conservation of built heritage in Scotland began around 1945 with many buildings being listed by the 1970s. Listed buildings and conservation areas in Scotland highlight national, regional and local importance, with the entirety of the building(s) being protected for future generations to enjoy. This research aims to help to highlight the need for protecting historic windows, one of the most vulnerable materials in buildings, and a material which is often overlooked as something that adds character or value to the building.

Amanda Pinto
Departamento de Conservação e Restauro, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus Caparica, 2829-516, Caparica, Portugal

19th century stained-glass windows of two mausoleums from Belém do Pará, Brazil: a characterization study
The mausoleums of Assis Chermont and Britto Pontes families, located in the city of Belém do Pará, northern Brazil, have spectacular stained glass windows produced in the late 19 th century, which were commissioned from France and Portugal, respectively. These panels have been exposed to tropical weather for more than a century without any preventive measure and the scientific investigation towards this valuable legacy is indispensable. Thus, the main objective of this work is to determine the chemical characteristics of 11 samples of 4 stained-glass windows from the mausoleums previously described and to identify the microorganisms existing on the biofilm which is deposited only on the surface of colourless glasses.

Manfred Torge
Bundesanstalt für Materialforschung und –prüfung, Berlin

Organic surface coatings on Mediaeval stained glass and microbiological investigation
Mediaeval stained glass has been treated with Polymethylmetacrylate coatings by Kwiatkowski 1 in Poland during the 1950s. Such treated panels were found in the Johannes Church of Torun (without protective glazing), in the Cathedral of Wloclawek (behind a protective glazing), and on glass kept in exhibition cases in the museum of Torun. Surface coatings have been detected and analyzed on the samples of Wloclawek and on samples of the museum of Torun, more than 60 years after the treatment occurred. No coatings have been found on samples in the Johannes Church, because of the direct weathering impact on the windows without a protective glazing during these years. In the SEM analysis of the coated samples evidence of microbiological growth have been found. The question to investigate was: Are organic surface coatings a source for enhanced microbiological activity?