Last year I was brought in to help restore a set of sandstone carvings on a heritage-listed building in inner Melbourne. The original carved elements, ornate capitals and decorative panels dating from the 1880s, had weathered badly. Large sections of detail were gone, dissolved by a century of acid rain and pollution.

Twenty years ago, restoring these pieces would have meant a skilled carver studying old photographs, making educated guesses about lost detail, and carving replacements freehand. The results depended entirely on the individual carver’s ability to interpret flat images into three-dimensional form. Good carvers produced good results, but there was always an element of interpretation.

This project was different. We started with a 3D scan.

How the Technology Works

Structured light scanners and photogrammetry rigs capture the three-dimensional geometry of a stone surface with extraordinary precision. The scanner projects a pattern of light onto the stone and cameras record how that pattern deforms across the surface. Software stitches these captures together into a detailed 3D model, accurate to fractions of a millimetre.

For heritage work, this means you can capture every remaining detail of a weathered carving before touching it. The digital model becomes a permanent record of the stone’s condition at a specific moment in time. That alone is valuable. But the real power comes from what you can do with the model afterwards.

From Scan to Restoration

With a detailed 3D model on screen, you can digitally reconstruct missing sections. If a decorative panel has surviving elements on one side but not the other, and the design was originally symmetrical, you can mirror the surviving geometry to fill in the gaps. If similar carvings exist on other buildings from the same period and architect, those can be scanned and used as references.

The reconstructed digital model then guides the physical carving. Some workshops use CNC milling machines to rough out replacement blocks from the digital file, with hand finishing by a trained carver. Others use the model purely as a visual reference, projecting it onto screens in the workshop while carving traditionally. Both approaches have merit.

For the Melbourne project, we used the scans to produce detailed technical drawings and 3D-printed reference models at half scale. The carvers worked from these references alongside the original stones, achieving a level of accuracy that would have been extremely difficult from photographs alone.

Applications Beyond Restoration

Heritage restoration was the obvious early use case, but 3D scanning is finding applications across the stone carving field.

Documentation and insurance. A full 3D scan of a finished sculpture provides a complete record for insurance purposes and for posterity. If a work is damaged or destroyed, the scan preserves every detail of the original.

Scaling and reproduction. A small maquette can be scanned and scaled up digitally, then used to guide carving at monumental scale. This is not new in principle. Sculptors have used pointing machines to scale up maquettes for centuries. But digital scaling is faster, more accurate, and preserves surface detail that mechanical pointing cannot capture.

Collaboration. A 3D model can be shared instantly with collaborators, clients, or engineers anywhere in the world. When I am working with an AI consultancy or an engineering firm on the structural aspects of a large installation, being able to share accurate 3D geometry rather than flat drawings makes the conversation immensely more productive.

Geological analysis. Scanning quarry faces and raw blocks can reveal bedding planes, fossil inclusions, and structural weaknesses before cutting begins. This reduces waste and helps carvers plan their approach to a block with more information than a visual inspection alone provides.

The Equipment

Professional structured light scanners suitable for stone scanning range from around five thousand dollars for handheld units to well over fifty thousand for high-precision stationary systems. For most sculptors, photogrammetry using a good DSLR camera and processing software like Meshroom or Agisoft Metashape is a more accessible entry point. The results are less precise than dedicated scanners but adequate for many applications.

What Scanning Cannot Do

It is worth being honest about the limitations. A 3D scan captures geometry, not material character. It tells you nothing about the stone’s hardness, its internal structure, how it will respond to the chisel, or how it will weather over the next century. These are things that only experience with the material can teach.

There is also a risk of false precision. A scan can give you a model accurate to 0.1 millimetres, but if the original carving was done with a point chisel and a sense of rhythm, reproducing it to that level of accuracy misses the point entirely. The best restoration carvers understand that the goal is not mechanical reproduction but sympathetic interpretation, capturing the spirit and technique of the original work.

The Future

The cost of scanning equipment continues to fall. Within a few years, I expect that 3D scanning will be a standard part of any stone conservation project, and increasingly common in sculptors’ studios.

For those of us who work with stone, these tools do not replace skill. They augment it. A 3D scan in the hands of a carver who understands stone is powerful. The same scan in the hands of someone who cannot read the material is just data. The craft remains the foundation.