Blog: Macroemulsions for the Cleaning of Polychrome Artworks and Removal of Organic Film Formers.

Macroemulsions for the Cleaning of Polychrome Artworks and Removal of Organic Film Formers
Reflections from Paolo Cremonesi's Advanced Workshop at CCNL 
Author: Bianca Gonçalves, June 10–12, 2025

This June, I had the privilege of attending an intense and highly informative three-day advanced workshop titled “Macroemulsions for the Cleaning of Polychrome Artworks and Removal of Organic Film Formers,” led by Paolo Cremonesi and organized by Restauratoren Nederland. Focused specifically on macroemulsions, the workshop offered a unique combination of up-to-date scientific insight, hands-on experimentation, and critical reflections on conservation ethics and environmental responsibility.

A Method, Not Just a Material
One of the most valuable takeaways was Cremonesi's perspective on emulsions: for him, emulsions are not just cleaning products but a methodological approach. By combining two immiscible phases—an aqueous phase and a non-polar solvent phase (eg, hydrocarbons or siloxanes)—macroemulsions allow us to utilize both extremes of polarity simultaneously, making them particularly effective in removing complex, aged, or mixed-media residues.

This is especially relevant in the cleaning of polychrome surfaces, where sensitivity to either water or solvent alone often limits treatment options. Emulsions offer the ability to deliver active agents more safely and effectively—even on surfaces sensitive to one of the phases—thanks to the emulsion's stabilizing structure.

Day 1: Understanding Macroemulsions
We started with a clear theoretical foundation: what macroemulsions are, how they differ from microemulsions, and why Cremonesi now considers microemulsions unstable and unnecessary in our practice. For him, microemulsions are officially out of the toolbox.

Cremonesi emphasized the importance of pH as the most critical parameter in solution formulation. While conductivity matters less, it can still influence performance. We discussed how most surface coatings on paintings are acidic or neutral—so if a surface tests alkaline, it might signal the presence of something unusual, like casein. As Cremonesi put it: “ Testing is a way of talking to the surface. ”

That first day we prepared buffer solutions, tested pH levels on mock-ups and paintings, frames, and objects, and got to know our testing surfaces. We worked in small groups, each preparing and sharing various solutions. This encouraged sharing of experiments and conversations, making the experience dynamic and collaborative.

Day 2: Emulsifying in Practice
The second day shifted into hands-on emulsification after a morning filled with theory. We prepared the based Pemulen, Xanthan and Carbopol gels, as well as a range of water-in-oil and oil-in-water emulsions, then tested them on our mock paintings.

It became clear how mechanical action is key—emulsions need physical interaction with the surface to be effective in picking up grime, varnish, or film-forming materials. Cremonesi provided mock-ups containing casein, allowing us to understand how pH-sensitive materials respond to emulsions and how crucial the formulation is to achieving desired results. We also started playing with a Green Solvent DBE, it was a new agent for many of us and had quite interesting results.

Day 3: Gels and Advanced Applications
Our final day explored various gel systems: agar, carbopol, pemulen, xanthan, and notably, silicone gels. We experimented with charging rigid agar gels with solvents, which showed promising results, particularly in frame cleaning applications.

Cremonesi shared an important (and somewhat bittersweet) insight: this may be the last time he teaches silicone-based emulsions, due to increasing EU restrictions around their toxicity. This is especially unfortunate for cleaning acrylics and in the case of the creation of double emulsions.

We also discussed specialized applications such as oxalate-related film removal and the concept of affinity emulsions. These advanced scenarios highlighted the potential (and complexity) of custom emulsion strategies.

Environmental and Regulatory Updates: What's Changing?
Personally one of the standout features of this workshop was Cremonesi’s candid and up-to-date insights on environmental safety and regulation, which will certainly impact conservation practice in the near future:

• Chelators are becoming restricted due to their environmental impact. Future availability may be limited.
• Borax is expected to be banned in the EU.
• Toluene, Xylenes, Shellsol A, CD5, and KSG-350z are all under threat of EU bans due to toxicity.
• Using the SH&E Criteria helps assess solvent safety, but in conservation, health and safety often take priority over environmental concerns due to our minimal use. For example, DMSO, though flagged environmentally, is safe in the studio and can reduce the need for larger quantities of a gentler solvent.
• DBE (DiBasic Esters) is a good substitute for benzyl alcohol. But again, always test!
• Cremonesi strongly advocates for rinsing solutions, even stating: “If you can't rinse, you shouldn't clean.” 
  He provided a volatile-solute recipe we can apply even in complex cleaning situations.
• There was also a strong call to stop using Tween 20, due to reports of pulmonary sensitization and other health effects.

Final Thoughts
This was a condensed three-day version of a workshop originally designed for four. The pace was demanding, and a working knowledge of chemistry—and some hands-on experience with cleaning—was essential to keep up. It was clearly geared toward advanced practitioners, offering not just skills but a mindset shift toward more precise, thoughtful, and sustainable cleaning practices.

Cremonesi, as always, blended rigor with humor, throwing in his signature “saucy jokes” while still delivering cutting-edge insights. The atmosphere was both serious and supportive, and the vegetarian lunches (with dietary accommodations) were excellent. We even had a few sunny moments in the beautiful patio at the CCNL.

This workshop didn't just update my techniques—it reshaped the way I think about emulsions, regulations, and the future of conservation science. I left with a stronger toolkit, a deeper understanding of cleaning dynamics, and plenty of inspiration for future research.

A special thank you to Willianne van de Sar for all the organization!