Restoration and conservation techniques are constantly evolving: materials and methods are updated based on new technologies and discoveries. To stay informed about the latest developments, we frequently organise workshops in our restoration studio where specialists share their expertise with us. In December 2024, we were particularly honoured by the visit of Dr. Ehab Al-Emam from Sohag University in Egypt. He earned his PhD at the University of Antwerp on the application of polyvinyl alcohol-borax/agarose (PVA-B/AG) systems for cleaning artworks.¹ Dr. Al-Emam successfully used this method to find a solution for removing deteriorated consolidant and thick soot layers from porous wall paintings in the temple of Seti I in Abydos, Egypt.^{2 3} Thanks to this method, aged varnish layers have also been safely removed from a wall painting in Antwerp.⁴

During the two-day workshop, our restorers were immersed in the theory and practice of PVA-B/AG systems, which we will refer to as ‘gels’ for simplicity. The first publication on the use of polyvinyl alcohol-borax (PVA-B) gels in restoration practice dates back to 2009.⁵ The application has been further refined and developed in recent years, including the combination with agarose (AG) gel‎. Blending PVA-B with AG gels creates a hydrogel with a double network. This has the advantage of bringing together the positive properties of the two systems while decreasing the negative ones. For example, PVA-B gel has low mechanical strength, causing it to adhere (or stick) to porous materials, potentially leaving residues on the artwork when peeled off. On the other hand, AG gel is very rigid and does not adhere to porous surfaces. However, its disadvantage is that it is rigid, making it almost impossible to adapt to the relief or structure. Thus, the contact with the artwork’s surface is not homogeneous. Blending PVA-B with AG gel results in a highly suitable medium for treating artworks as the gel can be safely peeled off from the (porous) surface without leaving residues. The workshop focused primarily on the preparation of PVA-B/AG gel and its application for cleaning paintings with discoloured varnish layers. It also included information on how to optimize several parameters to obtain the best cleaning results.

One of the key properties of PVA-B/AG gel is that it can retain liquids (including the cleaning agent) and release them gradually on the paint surface. This is particularly useful when the paint or the support of the painting is very porous. By placing the gel on the surface of the painting, the solvent in the gel can soften the varnish, allowing it to be partially absorbed by the gel and then removed shortly after with a cotton swab or compress. An additional advantage of the gel is that the contact time with the solvent can be precisely timed to avoid the penetration of the solvents into the sublayers of the painting and limit the cleaning action on the interface between the gel and the treated surface. Due to the gel structure, the volatile solvent also evaporates less quickly, which is safer for the restorer as they are less exposed to solvent vapours.

Practice leads to perfection. Therefore, our restorers will continue experimenting with the use of PVA-B/AG gels in the coming months. They will not only test and adjust the recipes as needed but also apply the gels in their various restoration projects. Specifically, they will focus on choosing the proper concentrations of the gelling material, the cleaning agents that can be incorporated into the gel, and the contact time between the gel and the artwork, in order to efficiently remove the varnish layers. Exciting times are ahead in the studio!

1. E. Al-Emam, Cleaning of Wall Paintings by Polyvinyl Alcohol–Borax/Agarose (PVA–B/AG) Double Network Hydrogels: Characterization, Assessment, and Applications, doctoral dissertation, University of Antwerp, 2021.[↩]
2. E. Al‑Emam, A. Ghafour Motawea, K. Janssens & J. Caen, ‘Evaluation of Polyvinyl Alcohol–Borax/Agarose (PVA–B/AG) Blend Hydrogels for Removal of Deteriorated Consolidants from Ancient Egyptian Wall  Paintings’, Heritage Science, 7, 22 (2019): 1-18, https://doi.org/10.1186/s40494-019-0264-z.[↩]
3. Al-Emam, E., Motawea, A.G., Caen, J. et al. Soot removal from ancient Egyptian complex painted surfaces using a double network gel: empirical tests on the ceiling of the sanctuary of Osiris in the temple of Seti I—Abydos. Herit Sci 9, 1 (2021). https://doi.org/10.1186/s40494-020-00473-1.[↩]
4. Al-Emam, E.; Beltran, V.; De Meyer, S.; Nuyts, G.; Wetemans, V.; De Wael, K.; Caen, J.; Janssens, K. Removal of a Past Varnish Treatment from a 19th-Century Belgian Wall Painting by Means of a Solvent-Loaded Double Network Hydrogel. Polymers 2021, 13, 2651. https://doi.org/10.3390/polym13162651.[↩]
5. E. Carretti, S. Grassi, M. Cossalter, I. Natali et al., ‘Poly(vinyl Alcohol)−Borate Hydro/Cosolvent Gels: Viscoelastic Properties, Solubilizing Power, and Application to Art Conservation’, Langmuir, 25, 15 (2009): 8656-8662.[↩]