Wax-resin linings were invented in the first half of the nineteenth-century and used extensively used until the 1970s. In those days approaches towards conservation were very different than they are nowadays. This is due to the introduction of codes of ethics that were developed since the 1950s by various conservation organizations worldwide. One point in common to all these codes is that the techniques and materials used for treatment should have “the least adverse effect on the cultural property” and “should not impede future treatment and examination.” Wax-resin linings however significantly and irrevocably affect the original characteristics of paintings. For example, after treatment the original canvas is covered by the adhesion of a second one and the paintings’ structure is fully impregnated with wax-resin causing colour changes and increased weight. The lining process involves warmth and pressure, factors that are potentially detrimental to the texture of painted surfaces. Furthermore, the saturation of paintings with wax-resin adhesive composed of materials known to be unstable upon ageing, is suspected to trigger chemical reactivity cause, for example, solvent sensitivity and soaps formation in the paint film. This condition is particularly problematic since to date, no safe method for reversing the treatment has been devised. Present conservators are confronted with the consequences of past treatments and should address paintings considering their physical history. However, with regard to wax-resin lined paintings, there is a lack of research into the effects of the technique on the material and physical characteristics of paintings.

The research programme of the Amsterdam Wax-Resin Project investigates various topics which correspond to three main lines of research: 

• History of wax-resin lining.
  • Historical development of wax-resin lining in the Netherlands.
  • History of the dissemination of wax-resin lining beyond the Dutch borders.
  • History of the critique of wax-resin lining.
• Impact of wax-resin lining on the physical and material characteristics of paintings.
  • Conditions and extent of colour change in paintings after wax-resin lining. 
  • Localization of the wax-resin adhesive in the structure of paintings.
  • Influence of wax-resin lining on the physical and chemical aspects of paintings, in particular canvas, ground and paint film
• Consequences of wax-resin lining for conservation practice.
  • Strategies for remedial conservation including, wax-resin extraction, de-lining and re-lining of wax-resin lined paintings.
  • Strategies for restoration of wax-resin lined paintings (cleaning, reintegration and varnishing).

Ongoing research on wax-resin lining at the University of Amsterdam

Emilie Froment is paintings conservator and lecturer at the University of Amsterdam (UvA). Her interest in wax-resin linings was triggered by the conservation of seventeenth century Netherlandish paintings in the Royal Palace Amsterdam in 2006-2010. The darkness of the monumental canvas paintings in the galleries was hypothesised as being a side effect of the 1960ies wax-resin treatment. Emilie examined the question of colour change in ground layers after wax-resin impregnation though her PhD that she received in 2019. Since then, the research on the topic is ongoing as new ground reconstructions are created regularly and are subsequently subjected to wax-resin impregnation and colour measurements. Currently, Emilie is developing an open-access database that will enable the sharing with professional conservators as well as researcher and students in conservation, of research results including photos and colour measurements. As lecturer at the UvA Emilie teaches master’s students in conservation and restoration of cultural heritage on the history and impact of wax-resin lining to paintings as well as on its consequences for conservation. She regularly supervises thesis on the topic of wax-resin linings. These research are developed in collaboration with the research group Conserving Wax-Resin Lined Paintings part of the Amsterdam Wax-Resin Project. Furthermore, Emilie coordinates the masterclass The Dutch Method Unfolded, a program for professionals in conservation, that receives the support of the Getty Foundation as part of its Conserving Canvas initiative.
Articles by Emilie Froment are in the list of references.

Ongoing research on wax-resin lining in The Netherlands

Esther van Duijn is paintings conservator at the Rijksmuseum. The history of wax-resin lining has been Van Duijn’s interest ever since she wrote her art history thesis in 1996 on Nicolaas Hopman, inventor of this technique, and his son Willem Anthonie Hopman. Although the history of conservation has been a consistent thread throughout Van Duijn’s career as a paintings conservator and researcher, this special interest took flight when she got the opportunity between 2015 and 2018 to carry out a fulltime research project into the conservation history of the paintings collection of the Rijksmuseum in Amsterdam. The history of the lining technique was a significant part of this research, since between 1845 and 1980 wax-resin linings were carried out on a large scale without alternative at the Rijksmuseum. An important new find was the elaborate notebook that the American conservator Louis Pomerantz kept when he studied in the Rijksmuseum paintings conservation studio in 1950 and 1951. It contains detailed text, drawings and photographs of the ‘Dutch method’. At the Rijkmsuseum this technique can be traced back in a direct line to its inventor Nicolaas Hopman. Since 2019 Van Duijn is part of the interdisciplinary team of the Operation Night Watch as a specialist in conservation history. This iconic painting by Rembrandt has been lined with wax-resin three times: in 1851, in 1945 and in 1975.
Articles by Esther van Duijn are in the list of references.

Mireille te Marvelde is a paintings conservator at the Frans Hals Museum in Haarlem. Wax-resin lining and its effects on paintings has been a topic of herinterest since 1994. In 1995-99 she was a member of the MolArt Research Project and together with scientists she studied the application of the wax-resin lining procedure and its effects on paintings. Research of this MolArt sub-group focussed on the behaviour of the wax-resin mixture during and after application, the degree of impregnation in the paint structure, and the ageing at the molecular level. As part of this topic Mireille investigated the history of wax-resin lining with the aim to construct a context for analytical research and to eventually know more about the current condition of wax-resin lined paintings. This resulted in detailed knowledge on the invention of the lining technique in The Netherlands and its principles as well as on the dissemination of the method throughout Europe and abroad. Furthermore, the research revealed specific approaches by restorers and showed how materials and techniques varied over time. Literature and archival research gave insight into the often opposing opinions on the positive and negative side effects of the method and in the developments that led to the abolition of wax-resin lining. An inventory of paintings in Dutch collections for whichlining date and name of the restorer was established. These paintings were excellent objects for research into the ageing of wax-resin and its long-term effects on paint layers. During the conservation project of the ‘Oranjezaal’ at the Huis ten Bosch Palace in The Hague, wax-resin lined and  unlined 17th century Netherlandish paintings were investigated by the MolArt team. Results were obtained on topics like the degree of impregnation, colour change and vulnerability of paint to solvent as a result of wax-resin lining. Research on wax-resin lining is to some extent continued at the Frans Hals Museum.
Articles by Mireille te Marvelde are in the list of references.