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 18th century ship wreck, and an experiment comparing residues left behind by various gels on paper.
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.
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.
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 18th century ship wreck, and an experiment comparing residues left behind by various gels on paper.
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 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.
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.
This blog post is the 2nd in a collection 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 first presentations of the first day kicked off the conference, setting the tone with intriguing philosophical, as well as practical hands-on examples of gels in conservation. The two leading conservation scientists in the field of gels, Richard Wolbers and Paolo Cremonesi, each provided an introduction to gels in conservation, what has been done historically, what is currently practiced, and thoughts for the future. Wolbers not only delivered the key note presentation, but spoke several times as collaborator for many of the talks and as a moderator. In his keynote address, Wolbers emphasized minimizing toxicity through substitution of less toxic materials and Cremonesi discussed the characteristics of agar gels and the current work being done with thermo-reversible rigid agar hydrogels.
Bottom line, it seems that the basic goal for many of the case studies that were presented is to find a way to safely use aqueous cleaning systems on water-sensitive materials without damaging the object. A tall order.
Richard Wolbers, keynote presentation, “Gels, Green Chemistry, Gurus and Guides”
Wolbers’ talk, “Gels, Green Chemistry, Gurus and Guides”, it provided an overview of gels in conservation, as well as a look towards the future, emphasized the goal of using Green chemistry, which involves less waste and is less toxic – something he has been advocating for years (here is the link to his talk: https://www.youtube.com/watch?v=RGpOYaU6owE).
Wolbers said, when confronted with a treatment problem, first determine if a gel is appropriate. Gels keep the gel and its contents in contact longer with the surface; gels make local application controllable or they can serve as a poultice. Naturally, the gel used shouldn’t impact the surface medium, and it should be non-toxic and clean the object. Wolbers listed some of the advantages of solid rigid agar gels: they dissolve in water, improve surface wettability, and have surfactant properties.
Ultimately, to do the best by our objects, we as a field need to continually look to other industries for ideas. For example, the cosmetic industry utilizes green chemistry to reduce exposure to potentially harmful solvents. We need to truly understand what we want to achieve in a particular circumstance and tailor it to our object, rather than relying on a few stock recipes and applying them to all situations. As conservators we must remain agile and stay creative. To do this we must understand the underlying principles of the materials we want to use and the objects we are treating. Conservation needs to be able to gain ideas and experience from other fields, and also be able to create and engineer our own materials to give us the type of control we need.
Paolo Cremonesi, “Thermo-reversible rigid agar hydrogels: their properties and action in cleaning”
In Cremonesi’s talk, “Thermo-reversible rigid agar hydrogels: their properties and action in cleaning”, (here is the link to Cremonesi’s talk, https://www.youtube.com/watch?time_continue=10&v=UbbxCQR4El8) he listed the advantages of agar gels: how they dissolve in water, and improve surface wettability. They have limited adhesion to the surface and, most importantly, leave behind minimal residue (as compared to gellan gum. (See M. Sullivan’s paper “Rigid polysaccharide gels for paper conservation: a residue study”). Past drawbacks of agar gels had been that they could only be applied to relatively flat surfaces. However, if the liquid gel is applied (brushed or poured on) just at the moment it starts to thicken, it can be used on a variety of surfaces, planar or not.
Thermo-reversible gels are often prepared in the microwave to prepare a homogeneous gel. When heated above 80F (Cremonesi recommended type E for its low gelling temperature) the gel is liquid and when cooled below 80F it is a solid. With increased concentration, the gel becomes stiffer which will slow the release of water from the gel. While in the liquid form it can be poured into receptacles such as a syringe body. Allowed to cool, once solid it can be kept in a “pencil” shape (this slide caused many audience members to swoon) or be cut into small plugs.
slide from Cremonesi’s presentation, grating agar plugs
At room temperature it can also be grated, with the shaving manipulated for surface cleaning. Enzymes mixed with Agar in a semi-solid state are the most effective form of the material. That said, Cremonesi said gellan gum is more appropriate for works on paper because it’s more flexible and transparent than agar.
One thing I’ve found with using gels (in my case gellan gum) is the formation of tide lines, which made me assume we were doing something wrong. According to both Wolbers and Cremonesi, I was missing a step. They talked about the importance of pre-wetting the surface to be treated with a non-polar solvent (they specifically mentioned D5, aka decamethylcyclopentasiloxane aka cyclomethicone). At first this might seem counter-intuitive: how does water work if there’s non-polar solvent in the way? Actually it’s about displacement – oil floats on water – so the water in the gel displaces the non-polar solvent to get to the surface. The non-polar solvent prevents tidelines principally by blocking capillarity. Now it’s all starting to make sense. The same principle was used by Burgio, Rivers et al (2008, Studies in Conservation) when consolidating matte paint. On this basis, any non-polar solvent (first spot tested) should work to prevent tidelines. D5 has the advantage of being a ‘green’ solvent, comes without the H&S hazards associated with hydrocarbon non-polar solvents, and is exceptionally non-polar.
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.
A couple of months have passed since I attended the London three-day conference “Gels in Conservation” co-hosted by the Tate and IAP (International Academic Projects, Ltd), better known as James (Jim) Black. You will know him from Archetype Publications; he’s the one who always remembers you.
Gels conference audience
The conference was the brainchild of Jim Black and Richard Wolbers, hatched over drinks and Indian food a few years back. They posed the idea, “wouldn’t it be great if we got all the people together working in gels? Scientists, conservators, students, etc., and shared what we know, or were working on in gels?” Apparently they were right, they weren’t they only ones who thought it was a great idea. More than 550 attendees from 39 countries attended the three-day conference. For me, and judging from fellow attendee’s responses, I can tell you it sure felt like a roaring success.
It was one of the most thoughtfully arranged symposiums I’ve ever attended. I suspect Jim Black may well be a genius and I hope other program organizers take note. There were three sessions each day, and each session started off with two or three talks about 25 or 30 minutes in length followed by several 10-minute talks. It kept things fresh and helped avoid listening fatigue. For the most part the 10-minute talks were just as informative as the longer format. At the end of each session the presenters had a panel Q&A with the audience. This gave people a chance to clarify and presenters an opportunity to add detail.
The conference was filmed/recorded, so take heart even if you didn’t get one of the sought-after tickets: you can still virtually attend, albeit slightly after the fact. Having the publication at the conference was brilliant. I can’t emphasize enough how excellent the publication is. It includes the papers from the presentations and the posters with great images. It was very helpful to listen to a talk then be able to refer to the paper immediately. Over the course of three days, some 41 authors presented research, techniques and ideas. Each day the talks were grouped together loosely by theme such as polysaccharide gel systems, which included agars, gellan gum and methyl cellulose, often compared or alone, sometimes with additives like enzymes or chelators. Day two, polysaccharide and polyacrylic gel systems, which included solvent gels, such as pemulen, and the new wave of solvents, silicone solvents. And finally, day three was entitled Novel and Multi gel treatment. Many speakers talked about trying to utilize less toxic materials as an alternative to “traditional” organic and aromatic solvents, moving toward greener alternatives. Authors shared their successes and failures, both being very informative. Many attendees, me included remarked that they really enjoyed the multi-discipline approach, learning what textile conservators and easel painting conservators are doing with the same sort of materials. It was very inspiring and informative.
The overall tone of the conference was one of hopeful optimism and desire for more research and development. Richard Wolbers spoke several times, first as the key note speaker and later as collaborator for many of the authors. He emphasized the need for conservators to look to other industries for potential products, greener or less toxic than what we use now, and to know the materials well enough to tailor them to our own specific needs for each specific treatment challenge. I came away inspired and intrigued. I have written companion blogs to this one and they will be posted in rapid succession. I hope I can convey some of what I learned and inspire you to obtain the publication and start reading. I will end with my favorite slide of the conference.
Your Plan vs. Reality.
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.
