The Use of Drone Technology for Thermal, RGB and Multi-Spectral Imaging in Stained Glass Restoration, Inspection & Cultural Heritage Documentation
Prepared by: Jerald H. Smith Technology Surveys & Inspections LLC
I am going to talk about two things that might not seem like obvious partners: stained glass restoration and drone technology. One is a craft that has been practiced for over a thousand years. The other is barely two decades old as a commercial technology.
But when you put them together — specifically in the context of documenting and assessing the scope of restoration projects — the result is a genuinely compelling market opportunity that is changing how artisans, architects, and building committees approach the preservation of some of our most treasured cultural heritage.
This presentation summarizes the findings of our market analysis report, and I want to leave you with a clear picture of where this market is, where it is going, and — most importantly — what it means for the professionals reading this paper.
Let me start with the problem, because it is one that everyone in the restoration industry knows intimately.
Stained glass windows in historic churches are typically located high above the floor — often 30, 40, or even 60 feet up in the nave, the clerestory, or the transept. Before any restoration work can begin, a conservator needs to get close enough to assess the condition of the glass: to see where the lead has failed, where the glass has cracked, where moisture has infiltrated, and where the structural support bars have corroded.
Traditionally, that means scaffolding, and scaffolding is expensive. For a typical large Gothic Revival church, erecting and dismantling a full scaffold system just for the assessment phase can cost anywhere from $25,000 to $80,000 dollars. This does not include the costs of the conservator onsite labor, transportation, lodging or insurance. It takes three to six weeks to set up. It disrupts services. It covers only a fraction of the building at a time, and it puts workers at significant risk of falls and major insurance exposure.
I am an experienced FAA Part 107 certified drone pilot and certified thermal imaging analyst serving conservators, architects and restoration consultants. I specialize in advanced data acquisition services for the documentation and assessment of stained-glass windows and their supporting structures.
Using cutting-edge drone sensor technology, I deliver high-resolution RGB imagery, thermal analysis, and multispectral data to provide a comprehensive view of existing conditions. This approach enables restoration professionals to make informed decisions, streamline project planning, and accurately define project scope based on reliable, non-invasive inspection data.
Historic stained-glass windows are among the most valuable and visually significant architectural artifacts found in churches, cathedrals, museums, government buildings, and historic residences throughout the world. Many of these works of art are centuries old and have been subjected to environmental exposure, pollution, moisture intrusion, ultraviolet radiation, structural movement, previous restoration efforts, and natural aging processes. Preserving these cultural treasures requires detailed documentation and accurate assessment of their condition before any restoration work begins. In recent years, multi-spectral imaging (MSI) has emerged as one of the most effective non-destructive technologies available to conservators for inspecting, documenting, and restoring stained glass.
Multi spectral imaging is a technique that captures images at multiple wavelengths across the electromagnetic spectrum, extending beyond the range visible to the human eye. While traditional photography records only red, green, and blue (RGB) wavelengths, multi spectral imaging records information in ultraviolet (UV), visible, near-infrared (NIR), and sometimes short-wave infrared (SWIR) regions. Each wavelength interacts differently with glass, pigments, metallic oxides, corrosion products, and restoration materials. By analyzing these responses, conservators can gain valuable insight into the composition, condition, and history of stained-glass panels without physically touching the artwork.
One of the most important applications of multi-spectral imaging is the identification and mapping of pigments and painted details. Historic stained glass frequently contains silver stains, iron oxide paints, copper-based pigments, enamel coatings, and other decorative materials. Over time, these materials may fade, deteriorate, or become obscured by dirt and weathering. Different pigments exhibit unique spectral signatures that can be detected through multi-spectral analysis. Conservators can use this information to distinguish original artwork from later additions, identify areas of pigment loss, and document the distribution of various colorants throughout a window. This capability is particularly valuable when planning restoration treatments or reproducing damaged sections.
Multi-spectral imaging also plays a critical role in detecting previous repairs and restoration efforts. Many stained-glass windows have undergone multiple repair campaigns over decades or centuries. Replacement glass, modern paints, epoxy adhesives, sealants, and protective coatings often differ significantly from original materials. Although these repairs may be difficult to identify under normal lighting conditions, they frequently become visible when viewed under ultraviolet or infrared wavelengths. By revealing these hidden interventions, MSI helps conservators understand the restoration history of a window and make informed decisions about future treatments.
Another significant benefit of multi-spectral imaging is its ability to reveal hidden or faded details. Near-infrared imaging can penetrate certain paint layers and surface deposits that obscure underlying features. Artist signatures, workshop marks, inscriptions, decorative patterns, and painted details that are nearly invisible in visible light may become readily apparent under infrared illumination. This capability allows conservators to recover important historical information without invasive cleaning or sampling procedures.
The technology is also highly effective for assessing glass deterioration and corrosion. Historic stained glass is susceptible to various forms of chemical weathering, including pitting, leaching, surface deposits, and crizzling. Crizzling is a common form of glass degradation characterized by networks of fine surface cracks resulting from chemical instability within the glass composition. These defects may begin long before they are visible to the naked eye. Multi-spectral imaging can identify subtle changes in surface reflectance that indicate the onset of deterioration, allowing conservators to intervene before significant damage occurs. By creating detailed condition maps, restoration teams can prioritize treatment areas and monitor changes over time.
Thermal imaging identifies moisture intrusion. This is another major concern in stained-glass preservation. Water can enter through deteriorated lead cames, failed sealants, damaged frames, or building envelope defects. Once moisture becomes trapped within or behind stained-glass panels, it can accelerate corrosion, biological growth, and structural deterioration. Infrared imaging techniques can help identify moisture accumulation and trace water pathways through glazing systems. These findings enable restoration specialists to address underlying building issues rather than simply treating visible symptoms.
Ultraviolet fluorescence imaging is often incorporated into multi-spectral inspection programs. When exposed to ultraviolet light, many materials emit visible fluorescence that can reveal otherwise hidden features. Biological growth, restoration adhesives, varnishes, coatings, and previous repair materials frequently exhibit distinct fluorescent responses. UV imaging allows conservators to map these materials quickly and accurately while documenting their location for future reference.
Modern conservation projects increasingly combine multi-spectral imaging with three-dimensional documentation technologies (digital twins). High-resolution digital photography, laser scanning, and photogrammetry can be integrated with spectral data to create comprehensive digital twins of stained-glass windows. These digital models preserve not only the geometry of the artwork but also its material characteristics and condition at a specific point in time. Such documentation provides an invaluable archival record and establishes a baseline for future inspections. Conservators can compare datasets collected years apart to identify progressive deterioration, evaluate restoration effectiveness, and support long-term preservation planning.
The benefits of multi-spectral imaging extend beyond individual panels to entire building facades. Large cathedrals and historic churches often contain stained-glass installations located high above ground level, making direct inspection difficult and costly. Advances in imaging platforms using drone-based sensing and photography, are expanding opportunities for remote condition assessment. High-resolution imaging combined with multi-spectral analysis can reduce the need for extensive scaffolding during preliminary evaluations while still providing detailed information about the condition of the glass and supporting structures.
A typical multi-spectral stained-glass documentation workflow begins with high-resolution visible-light photography to establish a baseline record. Multi-spectral images are then captured to identify coatings, biological growth, and restoration materials. Near-infrared imaging follows, revealing hidden details, under-drawings, and deterioration patterns. Additional spectral bands may be collected depending on project requirements. The resulting datasets are processed, aligned, and analyzed using specialized software to generate condition maps and restoration recommendations. Finally, all imagery and analytical results are archived as part of the project’s permanent conservation record.
As conservation professionals seek increasingly precise and non-invasive methods for preserving cultural heritage, thermal and multi-spectral imaging continues to gain importance within the field of stained-glass restoration. The technology provides unparalleled insight into material composition, hidden features, deterioration mechanisms, moisture intrusion, and prior restoration work. By enabling conservators to make informed decisions based on objective scientific data, thermal and multi-spectral imaging improves restoration accuracy, reduces risk to fragile artifacts, and enhances long-term preservation outcomes. As imaging systems become more accessible and analytical tools continue to evolve, thermal and multi-spectral imaging is expected to become a standard component of stained-glass inspection, documentation, and restoration projects worldwide.