Mist Consolidation
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Copyright: 2021. The Objects Group Wiki pages are a publication of the Objects Specialty Group of the American Institute for Conservation of Historic and Artistic Works. The Objects Group Wiki pages are published for the members of the Objects Specialty Group. Publication does not endorse or recommend any treatments, methods, or techniques described herein.
Introduction
In the fall of 2020, following a literature review, a survey was conducted to gather information about the way conservators use ultrasonic misters for the consolidation of under-bound matte paint. Summarized below are results from the literature review and survey.
What is Mist Consolidation?
Mist consolidation, or aerosol consolidation, is a method of delivering adhesives to objects with friable, powdery surfaces. The technique has been used in conservation treatments since it was established as a method for humidifying pastel works on paper by Marilyn Weidner in the 1980’s (Ream 2019). Stefan Michalski of the Canadian Conservation Institute then developed an apparatus that allowed adhesives to be applied via mist consolidation in 1990 (Maheux, McWilliams 1995). Mist consolidation is performed using a device called a nebulizer that generates a fine mist and delivers it through a tube. Types of nebulizers include pneumatic nebulizers, which deliver compressed gas through a jet, and ultrasonic nebulizers, which generate ultrasound waves that break up water into an aerosol mist. Adhesive solutions delivered via nebulizer are formulated depending on the needs of the object. The procedure should be performed and/or supervised by a trained art conservator and appropriate health and safety measures should be observed.
Health and Safety:
- Nebulizers generate microscopic particles that can enter the lungs, so wearing appropriate personal protective equipment (PPE) is crucial while undertaking this procedure.
- Wear a properly fitted respirator.
- Ensure the workspace has proper ventilation.
- Use gloves when handling objects.
Literature Review
Research indicated that using slow evaporating solvents in adhesive solutions for mist consolidation would be preferable for these types of objects as they would result in fewer tidelines and help retain a matte appearance (Hansen, Sadoff, Lowinger 1993, 1). Low viscosity consolidants were preferred for matte porous paints to help increase penetration and retain a matte finish (Hansen, Sadoff, Lowinger 1990, 166). Finally, as reported in the survey results, multiple applications of dilute solution were found to penetrate further with more satisfactory consolidation results (Hansen, Sadoff, Lowinger 1990, 166).
Survey Methodology
An electronic survey was distributed over a span of three weeks across multiple platforms, including several AIC and ICOM-CC working groups. 22 Responses were aggregated from these networks.
The survey included questions about devices used, preferred adhesives, diluents, and concentrations of adhesive solutions. Respondents were asked for general input on their experience with mist consolidation and were given the option to provide details about up to three mist consolidation treatments.
Survey Results
General Takeaways: multiple respondents reported problems with mist consolidation including difficulty regulating the amount of consolidant released and buildup of drips and clogs resulting in inconsistent application. These problems were common regardless of the device or adhesive solution used.
Devices: Respondents reported using devices ranging from custom nebulizers to homemade versions. Responses included both pneumatic nebulizers and ultrasonic nebulizers. Below is a list of the devices that conservators reported using:
- Devilbiss Pulmo-Aide Compressor Nebulizer (paired with disposable or reusable pneumatic nebulizer)
- AGS2000 Aerosol Generator
- Commercial Disposable Pneumatic Nebulizer
- Devilbiss Ultraneb Ultrasonic Nebulizer
- Recolo 100 Aerosol Generator Ultrasonic Atomiser
- Preservation Equipment Ultrasonic Humidifier
- Engelbrecht USV-5 Ultrasonic Atomizer
- Commercial Ultrasonic humidifier
- Omron C1 Silentio Compressor Nebulizer
Adhesive Solutions: Respondents reported using a range of adhesives for consolidant solutions including polysaccharides, cellulose ethers, animal glues, and acrylic resins. The most popular choice was gelatin, followed by sturgeon glue and methylcellulose. The most popular diluent reported was water. Most respondents reported using consolidant solutions at extremely low concentrations, with the majority less than or equal to 0.5%. The following graphs provide detailed results on adhesive and diluent selections.
Tips
Many conservators provided helpful tips when prompted to give general takeaways about their mist consolidation experiences. One user wisely advised: “the perfect equipment does not exist, so be patient.”
Before Treatment
- Prepare consolidant solutions at very low concentrations (less than 1%) to facilitate smooth flow.
- Use a black ceramic tile to check the direction and power of the mist before applying to the object.
- Mist the object with ethanol (when appropriate) before applying adhesive to reduce surface tension and allow penetration of the adhesive.
- For homemade devices, nozzles can be fashioned out of plastic pipettes and SugruTM[1] moldable glue for precise application.
During Treatment
Preventing Drips
- Empty the tube regularly and blot the tip of the hose with a paper towel or cotton pad during use to avoid the formation of droplets.
- Tape blotter to the end of the hose.
- Work with the object surface in a vertical orientation and keep the tube as straight as possible.
- Keep the device on a lower surface than the object being treated.
Working Methods
- Work under magnification to help control the location and amount of consolidant applied.
- Keep the nebulizer mist moving across the surface at all times.
- Apply multiple layers of adhesive solution at a low concentration, allowing drying time between applications. This approach is generally more successful than single high-concentration applications.
- Ensure the receptacle for consolidant is secured so it won’t spill or tip over while working.
- Keep the tip of the nozzle as close as possible to the object to avoid evaporation of the mist during travel.
Equipment Management
- Tape over any leaks where mist is escaping.
- Maintain proper level of water and consolidant in reservoir during use.
- Turn the device off and on if it stops generating mist.
After Treatment
- Avoid placing the object under weights after treatment; pressure is not necessary to achieve a bond.
- Dry the nebulizer membranes after use to prevent mineral buildup.
- Wash tubing carefully immediately after use with appropriate solvent (warm water, ethanol, etc.). Air dry thoroughly before storing. Mold can grow on the equipment, especially in the tubing, if it is not thoroughly washed and dried.
Further Research
- References that outline particle sizes and other product specifications for nebulizers.
- Identifying a device that can generate a consistent flow of mist without the formation of drips or clogs.
- Solutions for mist consolidating large-scale objects.
Bibliography
Geiger, Thomas and Françoise Michel. 2005. “Studies on the Polysaccharide JunFunori Used to Consolidate Matt Paint.” Studies in Conservation 50 (2005) pp 1-12.
Hansen, Eric F., Eileen T. Sadoff and Rosa Lowinger. 1993. “Consolidation of Porous Paint in a Vapor-Saturated Atmosphere: A Technique for Minimizing Changes in the Appearance of Powdering, Matte Paint. Journal of the American Institute for Conservation, Vol. 32, No. 1(Spring 1993), pp. 1-14. http://www.jstor.org/stable/3179647.
Hansen, Eric F., Eileen T. Sadoff and Rosa Lowinger. 1990. “A Review of Problems Encountered in the Consolidation of Paint on Ethnographic Wood Objects and Potential Remedies.” ICOM Committee for Conservation, 1990, Vol. 1, Working Group 3: Ethnographic Materials. pp. 163-168
Maheux, Anne F., Wanda McWilliams. 1995. ‘The Use of the Ultrasonic Mister for the Consolidation of Flaking Gouache Painting on Paper. The Book and Paper Group Annual 14 (1995). Accessed online 20 April 2022 at https://cool.culturalheritage.org/coolaic/sg/bpg/annual/v14/bp14-03.html.
Ream, Julie. 2019. “Mist Consolidation Workshop.” Presentation at Winterthur/University of Delaware Program in Art Conservation, Winterthur, DE, October 18, 2019.
Turner, Nancy. 2008. “The AGS2000 Aerosol Generator: Creating A Mist Consolidant for Non-Contact Media Consolidation.” WAAC Newsletter vol. 30, no.3, September 2008. https://cool.culturalheritage.org/waac/wn/wn30/wn30-3/wn30-307.pdf
Welsh, Elizabeth C. 1980. “A Consolidation Treatment for Powdery Matte Paint.” In Preprints of Papers Presented at the 8''' Annual Meeting, San Francisco, Ca., May 22-5, 141-148. Washington D.C; AlC (American Institute for Conservation of Historic and Artistic Works), 1980.
Other Resources
Dignard, Carole, and Stefan Michalski. 1997. “Ultrasonic Misting. Part 1, Experiments on Appearance Change and Improvement in Bonding.” Journal of the American Institute for Conservation vol.36, no. 2, pp. 109-126. Accessed online 20 April 2022 at https://cool.culturalheritage.org/jaic/articles/jaic36-02-002_indx.html
Pataki Hundt, Andrea, and Eva Hummert. 2016. “Colour Stability of Natural Adhesives - Light Ageing of Adhesive Films and Colour Changes of Pigment Layers after Aerosol Application.” Restaurator: International Journal for the Preservation of Library and Archival Material vol. 37 iss. 2. Accessed online 20 April 2022 at https://www.degruyter.com/document/doi/10.1515/res-2015-0020/html?lang=en.
[1] “moldable glue” adhesive repair putty. Available from craft suppliers.
