Carolyn Horton grant – AIC Blog Archives: Conservators Converse

The London Gels in Conservation Conference: Michelle Sullivan, “Rigid polysaccharide gels for paper conservation: a residue study”

Gels in Conservation Conference, October 16-18, 2017

This blog post is part of a series of observations about the London “Gels in Conservation” conference co-hosted by the Tate and IAP (International Academic Projects, Ltd). In mid-October, over the course of three days, some 41 authors presented research, techniques and ideas on gels in conservation. The talks were excellent, and I’ve focused on four that were notable for the wide range of materials treated and challenges faced. They ranged from coating/grime removal from a giant sequoia tree cross section, to dirt and varnish removal from Delacroix wall paintings, to removal of repairs from a fragile felt hat from a 18^th century ship wreck, and an experiment comparing residues left behind by various gels on paper.

Sullivan's research questions — Sullivan’s research questions

The fourth talk I wanted to highlight is Michelle Sullivan’s “Rigid polysaccharide gels for paper conservation: a residue study” — of particular interest to me as a paper conservator. It was one of the few studies exploring quantitatively if residue is left behind by gels used in the treatment of works on paper. If so, did how does that residue impact the paper? To easily track residue on the paper samples, fluorescein dyes visible in UV light were added to the gels tested. The experiment used agarose, gellan gum and methyl cellulose gels in three different concentrations applied to three different papers for three different time periods. In addition, a few variables were added to mimic treatment, such as applying the gels through Japanese paper and clearing the gels using a damp swab. Besides surface examination, cross sections of the samples were also taken to see if the gels were penetrating the paper surface. The cross sections seemed to suggest that gellan gum was being absorbed into the paper. Sullivan found that all the gels tested left a residue, with gellan gum apparently leaving behind the most. She found that applying the gels through a Japanese paper barrier was the most effective method in minimizing residue. After oven aging for 21 days, the rag sample treated with gellan gum darkened slightly, while all the other samples did not. Sullivan proposed that the darkening might be related to the gelatin content of the rag test paper. She plans to expand her test variables and continue to build on this research. This feels like very important research and I eagerly await to results of the next phase of her work.

image of the gels & papers used in experiment — Gel residue experiment set-up.

This blog series is a result of receiving the FAIC Carolyn Horton grant to help me attend the conference. I would like to gratefully acknowledge the FAIC for helping make it possible for me to attend this important conference.

The London Gels in Conservation Conference: Jonathan Clark, “Revisiting a shipwrecked felt hat for Chatham Historic Dockyard Trust: a multidisciplinary approach”

Gels in Conservation Conference, October 16-18, 2017

2.Image of felt hat during treatment using gel and spider tissue to remove old repair. — 2. Image of felt hat during treatment using gel and spider tissue to remove old repair.

Jonathan Clark’s presentation, “Revisiting a shipwrecked felt hat for Chatham Historic Dockyard Trust: a multidisciplinary approach” featured a really cool felt hat from a 1758 shipwreck. The project resulted in an unusual opportunity for collaboration between a textile and an objects conservator–both bringing needed experience to successfully treat the hat. In the past, the object had been treated aggressively with layers of synthetic materials and heavy cardboard fills. The hat was misshapen as a result of the thick repairs, making it difficult to fully see the original object. The treatment objective was to release the fragile felt hat from its past repairs and reshape it to its intended form without harming the object. Acetone softened the thick unknown adhesive, so both acetone vapor and solvent gels were used to release and reduce the adhesive. The acetone solvent gel was applied through spider tissue, a very soft and strong paper (100% manila fibers). Once in place, the spider tissue was pre-wetted with methylated spirits, then the gel was applied via spatula, which was then covered with plastic wrap to slow evaporation. Once the old repairs were removed the hat remained misshapen, to further soften the remaining adhesive holding the felt hat out of shape, it was placed in an acetone vapor environment. The softened pliable hat was then weighted and pinned to a Fosshape form, a shrinkable polyester felt, used by textile conservators to create mounts. The end result was an object that was stable and could safely be stored showing only its original materials.

Felt hat after treatment pinned to Fosshape form.

The London Gels in Conservation Conference: Alina Moskalik-Detalle, “Conservation of murals by Eugene Delacroix at Saint Sulpice, Paris”

Gels In Conservation

2.Alina Moskalik-Detalle talking describing coating removal — 2. Alina Moskalik-Detalle talking describing coating removal

In the second of four talks, Alina Moskalik-Detalle presented “Conservation of murals by Eugene Delacroix at Saint Sulpice, Paris.” The talk was interesting for its scale and challenges. Because I’ve gone to see these murals many times over the years, the talk was also personally interesting. Each time I visited, I left somewhat disappointed by the darkened, flat, dull murals. As luck would have it, I was scheduled to travel to Paris a week after attending the gels conference. What I saw when I visited Ste. Sulpice was truly remarkable—color, depth, and drama. The cleaning had totally transformed these murals. Naturally, I couldn’t help myself, I actively looked for shiny patches—the results from this treatment were remarkable. This multi-year project involved numerous conservators including collaboration with Richard Wolbers. Some of the treatment challenges included flaking paint, complex paint layers, multiple restorations, rising damp in the walls, carbon based grime, and, if that wasn’t enough, the paint was very sensitive to organic solvents. The conservators wanted to limit penetration of their solvent gels without leaving a residue or tide line behind. They wanted good contact between the gels and the substrate, control of the action of water, and to create mixtures of solvents that would clean effectively without damaging the paint layers. After cleaning tests were performed, a treatment protocol emerged: by pre-saturation of the areas being treated with cyclomethicone followed by the application of silicone solvents gels to the mural’s surfaces, tide lines were avoided, grime could be removed, the gels could be cleared, and residue was limited. The D4 was a slow evaporator which allowed about a 30 minute working time for the application of the gel and subsequent grime removal without harming the paint layer.

during treatment, Delacroix mural detail — 3. Delacroix mural detail, during treatment

The gels were made and applied in a paste-like consistency for maximum control of where the material was placed. It clung to the vertical walls and horizontal ceiling long enough to be effective. Using D4 based emulsions to clean the mural’s paint surfaces allowed the removal of surface soil without stripping wax or oily components from the paint films themselves. Because the emulsions were surfactant free, it was easier to clear them from the treated surfaces. Analysis of samples didn’t show residue left behind on the surface, but when the conservators tried to consolidate flaking areas of paint, they had trouble with adhesion, it is unclear why. It will be interesting to see how these murals age over time and if further treatment is needed in future, how re-treatable it is.

St. Sulpice chapel after conservation treatment — 4. Author pictured in Delacroix chapel after treatment was completed.

The London Gels in Conservation Conference: Lu Allington-Jones, “Giant sequoia: an extraordinary case study involving Carbopol gel”

Gels In Conservation

Giant sequoia section displayed in the central hall of the Natural History Museum

The first session of four, “Giant sequoia: an extraordinary case study involving Carbopol gel”, was presented by Lu Allington-Jones and was intriguing for several reasons: the object was enormous–5 meters (over 16 feet) in diameter. The size alone produced significant challenges, for which solvent gel was particularly suited. The scale meant that it would be treated in situ in full view of the public, thus potentially exposing patrons to chemical fumes; it would require large amounts of materials to treat; and it was at the top of an open staircase, meaning significant height came into play, as well. The giant sequoia cross-section had been on continual display since 1894, so it was incredibly dusty, had a darkened and cracking lacquer coating, and had a very friable bark around its perimeter. A material was needed that could safely remove the failed coatings and accumulated dust without penetrating the surface, harming the friable bark, or creating an unsafe environment for the conservators and patrons during treatment. Using a solvent gel had the advantage of keeping the solvents contained, reducing solvent vapor, and could act as a poultice to reduce grime and solubilize the failed coating. In addition, because gel ensures contact with the treated surface, it means that a lower concentration of solvent could be used as compared to a free liquid solvent. The gel was made 24 hours ahead in Ziploc baggies, the time allowed the gel to reach the needed smoothness and viscosity.

Applying solvent gel from zip-lock baggie (left). Removing solvent gel after treatment (right). — Applying solvent gel from plastic baggie (left). Removing solvent gel after treatment (right).

For application, the Ziploc bags were cut open at one end, the gel squeezed out and spread to 20 mm thick (about ¾”), then covered with plastic wrap to slow evaporation, giving the conservator about an hour of working time before the gel became too sticky and unworkable. Once the gel softened the coating, it was then removed trowel-like with a piece of cardboard, repeated, then cleared with industrial methylated spirits and wipes. A significant lesson learned about the gel was once it reached 73F or more, it became runny, causing the gel to slip off the vertical surfaces being treated, which didn’t allow enough working time to reduce the surface coating adequately. Once treated, the cross section was varnished with a protective layer of Laropal A81. The cross section looked amazing in the after images. I would encourage everyone to read the article in the post prints as it describes the details of challenges, decision making, and final outcomes.