As the hot and humid summer days approach, it’s important to understand the environmental factors that can directly damage the timeless, beautiful artwork, breathing life into any historic building. Murals and fine artwork enrich our built environments with beauty, culture, and history. Whether in a cathedral, a historic theatre, or a public building, these artistic expressions require special care to remain intact for future generations. One of the most invasive threats to decorative artwork, especially murals on plaster and canvas, is the presence of moisture, leading to the growth of mold and mildew.
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At John Canning & Co., we’ve seen firsthand how moisture damage can compromise both the structure and the aesthetic value of historic artwork. Fortunately, there are proactive steps that can be taken to reduce the risk and ways to preserve the artwork if it's already been damaged by mold or mildew. Below, we will explore the risks of mold and mildew, measures you can take to prevent them, and what to do if you catch mold invading your artwork or mural.
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Understand the Risks: Why Mold and Mildew Form |
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Mold and mildew are both types of fungi that thrive in damp, poorly ventilated environments, and it’s extremely important to be hyper-aware of this during the more humid days of the year. The combination of warmth and moisture in the air creates an ideal breeding ground for fungi. |
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Mildew typically grows on the surface of damp, organic materials like fabric, paper, leather, and walls and appears as a thin, powdery or fluffy growth, often white, gray, or yellow, and has a musty odor. Mold tends to be black, green, blue, or even red, and is often fuzzy or slimy in texture. Mildew is typically less invasive than mold and grows on the surface of materials, while mold penetrates deeper. Which makes mildew easier to clean as it’s mostly a surface-level issue, whereas mold can cause significant structural damage, staining, and deterioration, especially in buildings and artworks, and is significantly harder to remove. Both can appear on surfaces like walls, ceilings, and artwork when moisture is present, making it very harmful not only for causing structural damage but also posing a health risk, including respiratory issues, allergies, and irritation.
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Moisture can enter a historic building in several ways, creating conditions for these fungi to grow. Common sources include roof leaks, cracked or deteriorated masonry, and damaged gutters or downspouts that allow water to seep into walls and foundations. Poor ventilation and outdated HVAC systems can also lead to trapped humidity inside the building. Over time, these issues create a humid environment where mold and mildew can thrive, especially if not promptly addressed. Once the fungi take hold, they not only create unsightly blemishes but can also deteriorate paint layers, weaken plaster substrates, and even lead to irreversible staining.
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Mold and mildew can cause a range of paint damage to historic artwork and murals, including discoloration and staining, loss of paint adhesion, cracking, peeling, and flaking of paint layers, weakening of the canvas or paper support, and ultimately, the potential for irreversible damage and loss of the artwork. Artworks are especially vulnerable in spaces that were not originally designed with modern environmental controls, making prevention strategies all the more critical.
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Key Prevention Strategies |
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1) Control Humidity and Temperature |
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The most effective way to prevent mold is by maintaining stable environmental conditions. Ideally, relative humidity should be kept between 40-60% with a stable temperature in the range 65-70°F with minimal fluctuations, since that can be just as damaging as extreme humidity and temperature levels, so always aim for gradual changes. Depending on the artwork’s materials, condition, and history, the range can differ. It’s always best to receive an evaluation from a conservator to establish the appropriate environmental conditions for specific pieces.
A well-calibrated HVAC system is essential. In historic buildings, this often requires integrating modern systems in a way that is sympathetic to the architecture and does not disturb the original historic materials. Regular maintenance and monitoring of HVAC units are vital for keeping the environment stable year-round. |
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Good air circulation prevents the stagnant conditions that mold and mildew require to thrive. This is particularly important in buildings with heavy masonry walls, basements, or areas where air movement is naturally limited. Consider using mechanical ventilation, such as dehumidifiers or fans, in spaces prone to dampness. For structures without central air systems, portable solutions may be a short-term fix, but long-term plans should prioritize integrated solutions tailored to the building’s unique construction and materials.
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Routine inspections of roofs, ceilings, gutters, and exterior masonry are essential. Water ingress from a leaking roof or a poorly sealed window can introduce moisture into the walls and ceilings, putting nearby murals at risk. Even decorative surfaces that appear stable may be hiding moisture behind their substrate. Methods such as using non-invasive moisture meters can help detect hidden issues without damaging artwork.
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Once preventative measures are in place, ongoing monitoring is key. You can install humidity and temperature sensors in vulnerable areas, especially attics, basements, or behind walls with murals. Along with using data loggers, which can provide long-term insights that help building stewards identify patterns and respond to any infiltration before significant damage occurs. Historic buildings with any fine artwork or murals should have routine maintenance checks with a visual inspection of the artwork and surrounding walls. Artworks should also be continuously monitored for telltale signs of mold or mildew, such as discoloration, musty odors, or flaking paint, all of which may indicate an early mold issue.
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What to Do if Mold Appears |
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If you suspect mold or mildew on your historic mural or fine artwork, it’s crucial not to attempt cleaning it yourself, especially without a professional assessment. Some molds are at high risk of health concerns, and performing typical cleaning acts such as using vinegar, bleach, or even certain soaps can permanently alter paint pigments and cause even more damage.
Our conservators at John Canning & Co. are trained to assess, contain, and reverse damage in ways that protect both the artwork and the people interacting with it. Early intervention is essential; the longer mold is present, the more likely it is to penetrate through paint layers or weaken plaster substrates. |
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Mold and mildew may be invasive, but the fight against them is possible with experienced conservation practices, thoughtful environmental control, and a deep respect for the materials and stories these artworks embody. We’re committed to helping historic buildings safeguard their artistic and architectural heritage. Whether you’re overseeing a historic church, a capitol building, or a decorative interior, taking a proactive approach to mold prevention ensures that these spaces can continue to inspire for generations to come.
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Latest Articles & Announcements |
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| 14 Types of Ornamental Woodwork in Historic Buildings |
Ornamental woodwork in historic buildings may be otherwise understood as the appropriate architectural proportions of interior ornament carved from wood. The definition of the word “ornament” is understood to be “something that lends grace or beauty; a manner or quality that adorns”(Merriam Webster, def. 2). Therefore, the type of wood utilized and level of detail will influence the overall aesthetic and quality of an ornamental carving. In most cases, ornamental woodwork has an underlying structural function or purpose that has been subsequently adorned on the face. In this blog, we provide a few types of ornamental woodwork that, one may be able to identify in any construction from a historic home to a church.
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| How to Raise Funding for a Historic Theatre Restoration |
The League of Historic American Theatres (LHAT) conference is about to kick off and we are preparing for the largest conference in the League's history. So, we thought it would be a great time to share an article on raising funds for a historic theatre restoration. Raising funding for a historic theatre restoration requires a strong project team, a comprehensive strategy, a project budget, and a comprehensive scope. When fundraising for a theatre restoration, there are a few strategic plans to keep in mind. In this blog, we will provide a checklist to help guide the fundraising process.
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We are proud to be a part of the Salt Lake Temple project. Exceptional is not only the word we use to describe this Temple project, but it also reflects the level of our experience with this client. We are excited to continue our work at the Salt Lake Temple and observe its progress toward completion. We know the final results of the renovation will be magnificent. Take a look for yourselves in this recently released video on the project, featuring the Salt Lake Temple renovation over the past five years. The video shows the progression of the temple's renovation starting in 2019 until recently, as it enters its final stages of completion. Click here to watch the video and see a few familiar faces!
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Back in May, a division of John Canning & Co., Canning Liturgical Arts, received an Honor Award for Religious Architecture/Restoration on the design and decorative paint work at the San Joselito Adoration Chapel. “A stunning transformation, which is just beautiful. It invited you into worship—a place where spirituality happens. This is an example of how a lot can be done with a little” (Jury Comments). Coming up on July 23rd, you can meet the latest Faith & Form Award winners during the free virtual presentation from 12-2 pm EDT. Hear from winners and jurors, including remarks by President, David Riccio. AIA members earn 2 LUs. To register click the link.
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We had a wonderful time at this year’s Folklife Festival held by the Smithsonian. It was held on the National Mall in Washington, D.C. from July 2-7th. The theme was “Youth and the Future of Culture,” which explores the different ways that young people influence and engage with culture, and how they create, innovate, and sustain cultural practices and traditions. The festival promotes traditional building trades and celebrates cultural traditions from around the world through music, art, food, and storytelling, highlighting the importance of traditional skills in today's world. Three generations of Canning talent were featured through participating in Shop Talks and doing demonstrations to provide a glimpse of our decorative painting skills. One of which was demonstrating some of our woodgraining techniques. Check out clips from our time at the festival on our social media, which are linked at the bottom of the page. Thank you to everyone who stopped by our booth!
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Last month, Canning received the Traditional Building's Craftsmanship 2025 Palladio Award for the First Church of Christ Interior Finishes project. The annual Palladio Awards honor outstanding achievement in traditional design and recognize both individual designers and design teams whose work enhances the beauty and humane qualities of the built environment. Click here to read the project award write-up in Traditional Building's Magazine.
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Don’t miss out on this year’s PastForward conference by the National Trust for Historic Preservation, held in Milwaukee, WI. You can also participate by joining their livestream. The conference is from September 16-18 and will be discussing and raising awareness to strategize and advocate for policies and funding that ensure preservation continues to serve the public. You will discover new ideas for engaging audiences, gain insights on how to respond strategically to challenges, learn powerful ways to raise awareness, and understand ways to preserve a complete history of America through its places. If you’re a craftsperson, artisan, preservationist, or want to be involved in preserving America’s history, this is a great opportunity. To learn more about the conference, click here.
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Looking for something to do during your summer break? Check out the Institute of Classical Architecture & Art New England’s upcoming event on Saturday, July 26th, where you can learn about the history of the Rough Point Estate in Newport, RI, and sketch its architecture and landscape. Participants will follow in the great tradition of architects and artists by learning to draw in situ. The program focuses on the enduring vitality and continuity of the classical tradition through the means of observational and analytical drawing. The course is from 9:30 am until 4 pm EDT and will begin with a brief introduction to the history of the site, and will talk about various drawing techniques for drawing in situ. Guidance from instructor, David Pearson, whose former work as Senior Designer at Fairfax and Sammons focused on the urban form, will be provided as well. Don’t miss out on the chance to view, learn about, and sketch Newport’s beautiful architecture this summer. If you’re interested in attending, click the link.
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Interested in Seeing More of Our Work? Follow Us on TikTok!
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Watch our skilled preservation experts perform a portion of the mural cleaning process. This is a delicate process that involves prior research of the painting and its materials, as well as careful preparation and execution to ensure the artwork is not damaged during the process. |
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We understand the importance of sharing our expertise and knowledge in our field. Besides the monthly newsletter and blogs we post, we also develop and share downloadable resources to help guide you in your conservation, preservation, and restoration projects. Check out the Resources page and see if any of the resources can help answer some of your questions and provide a better understanding of some of the intricacies in the preservation field.
Check out our Featured Downloadable Resource below. |
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One of the most crucial parts of historic preservation is the restoration of painted surfaces. If you're looking to hire a paint restoration contractor, it is imperative to know what to expect from the process. Our guide to Hiring a Paint Restoration Contractor shows you how to know what to look for in a contractor, what to expect from the contractor, and gain an understanding of the process of historic paint restoration.
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The Association for Preservation Technology (APT) is the premier cross-disciplinary organization dedicated to promoting the best technology for conserving historic structure and their settings.
Annual Conference November 11-15, 2025
Providence, RI |
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As a national nonprofit preservation organization, the National Trust for Historic Preservation works to save America's historic places and is a great resource for anyone looking to learn more or get involved. Annual Conference September 16-18, 2025 Milwaukee, WI |
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The League of Historic American Theatres (LHAT) is a non-profit organization with the main purpose of sustaining historic theatres across North America for the benefit of their communities and future generations.
Annual Conference July 20-23, 2025
Pittsburgh, PA |
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The American Institute for Conservation and the Foundation for Advancement in Conservation work together to promote the preservation and protection of cultural heritage. Partner with us to further that mission.
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JOIN THE CONVERSATION #PerfectingPreservation #jcanningcrew |
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