This summer, LACMA launched a YouTube video series, ART + WORK, which shows the care that museum conservators put into preserving a wide range of artworks from our permanent collection. 

In this video, former Andrew W. Mellon Fellow in Paintings Conservation Caroline Hoover uses an innovative technique to clean a 1912 painting by Ernst Ludwig Kirchner titled Still Life with Jug and African Bowl.

Below, Caroline explains more about how she came to use these nanogels for this treatment. 

Tell us about how this painting ended up in the Paintings Conservation lab.

Kirchner is a founding member of the very influential German Expressionists group “Die Brücke,” or “The Bridge” in English. It was formed in 1905 and he created this group with other important German Expressionist painters. The group worked together to make paintings composed of bold, unrealistic colors. 

Knowing some other paintings by Kirchner, you know that he's pretty  well known for these dry, matte surfaces. This painting was very glossy and it seemed a little flat, which often happens when varnishes degrade and turn yellow over time. The painting loses its depth. That’s why we decided to treat it. We also wanted to get it ready to be reinstalled  in the new modern art galleries.  

What kind of analysis of the painting did you perform in order to select a treatment?

We used multiple photographic techniques to visually examine the painting and the varnish. We also used a number of scientific analyses in order to try and find out information about the layering structure of the painting and the composition of the paint itself, as well as the varnish. 

We began by doing some preliminary tests using traditional techniques to learn more about the painting. We took a very small, microscopic sample of paint and embedded it in resin, which is called a cross section. A cross section allows us to look at the stratigraphy of the paint layers under a microscope and see the ground, the paint, and the varnish. It allowed us to see that the varnish was fairly thin and confirm that it was present. 

From the cross sections, we found out that the varnish was likely a water-based polyurethane varnish, which is quite unusual for paintings. This type of varnish is usually something that's used to coat wood. This information helped us determine a treatment plan for reducing the unique varnish. 

Tell us how you came to use the nanogels to reduce the varnish. 

After learning about the construction and the materials of the painting, we tried some traditional techniques to reduce this unusual coating. Unfortunately, we were not completely satisfied with any of these. 

Shortly thereafter, Diana Magaloni, the new Head of Conservation, invited Professor Piero Baglioni of the University of Florence to give a lecture to LACMA. Professor Baglioni is a world leader in innovative new materials and methods for conservation. He shared with us this new product, developed by his team, for conservation: the Nanorestore Gels®. They're made by the Research Center for Colloids and Nanoscience in Florence and they're made specifically to address the complex nature of modern and contemporary artworks. Modern and contemporary artworks have moved away from traditional techniques, in a lot of cases, and can feature many different types of new materials and techniques, such as in the composition of the paints used, the way the paint is applied, et cetera. It can be very different from the traditional way that paintings were made. As a conservator, you often run into challenges because of the wide variety of materials and techniques that modern and contemporary artists can use. Specifically with Kirchner, he was known to sometimes add wax to his paints in order to make them look more matte. Therefore, for this specific painting, due to its unique coating and challenges for reducing it, we thought the Nanorestore Gels® would be a good treatment option to explore and test.  

Tell us more about the Nanorestore Gels®. 

They all operate kind of like a sponge. They have a scaffold network that they're composed of and they will hold a solution in that scaffold. When you apply it to a surface, the solution that's held in that scaffold interacts with only that top layer that you're trying to address. It will de-wet the surface, which is the opposite of wetting a surface. It will allow that specific material that you're trying to remove to be selectively separated from the layers below it.

We ordered the gels from the University of Florence and once they arrive, they suggest that you take the gels out of the solution that they're shipped in and put them into deionized water, which would allow the solution the gels are shipped in  to exchange out, bringing the surrounding deionized water into the gel. The next day, we would exchange the water for new water. We do this four times and basically we are rinsing out the solution that the gels are shipped in, just to make sure that they're holding only deionized water. After the fourth day, you can put the gels into whatever cleaning solution you're using.

Please describe how you clean the painting using the gel.

When we clean, we kind of clean in these organic shapes. We don't really clean in hard-edge squares. So I wanted to mimic the traditional way of cleaning a painting with the shape of the gel that I cut. I also wanted the shapes to all fit together so I didn't miss any areas or have any boundary lines between the gels. 

What was really nice about the gels is that we didn't have to use any mechanical action on the surface of the painting. Kirchner’s paints are often underbound, so they don't have a lot of binder in them. For this reason, having mechanical action and rubbing on the surface, which would have been a traditional cleaning technique with a cotton swab, isn't so ideal for this particular painting. 

This gel, the way that it works, and the properties of it allowed me to very gently remove this varnish without having to rub the surface.

What was particularly challenging about this treatment? 

Conservation itself is not usually a one size fits all, but specifically with these gels, they are new. We're learning about them, testing and researching them, and just starting to try them out. I think there's a lot more to be learned about them. They worked out really nicely for this treatment and they will be a great additional treatment option in the conservator’s toolkit, but I think there is a lot more to be learned and a lot to explore with them for other scenarios.