Original Work
- Author: John Giles Eccardt (1720, Germany-1779 Chelsea, London)
- Title: Portrait of Sir Robert Walpole and Catherine Shorter
- Materials: Oil on canvas, in a carved frame in the stle of Grinling Gibbons, gilt and black.
- Mesurements: 50,8 x 101,6 cm
- Location: Since 1930, June, The Lewis Walpole Library, Yale University.
The portrait of Sir Robert and Lady Walpole before removal of frame for recording.
Recording the original painting
A team of Factum Arte’s experts carried out the digitisation of the painting at the Lewis Walpole Library in October 2015. Various complementary systems were used: the Lucida 3D Scanner for high resolution recording of the canvas’ relief, panoramic composite photography to accurately record the painting’s colour and photogrammetry to obtain 3D and colour information of the frame.
Laura O'Brien Miller, Conservator at Lewis Walpole Library, inspecting the painting.
Once the canvas was removed, the shape of the frame was recorded with photogrammetry. Photogrammetry is a technique for obtaining 3D information out of an object by taking multiple color photographs with high percentage of overlap. Once these photographs are processed, the result is a virtual 3D model.
Gabriel Scarpa from Factum Arte photographing the frame as part of the photogrammetry recording
The technique of taking multiple photographs of an object to obtain 3D information is known as photogrammetry.
For the frame's digitization, a total of 500+ photographs were taken from every angle.
The canvas’ surface was recorded with the Lucida 3D Scanner. The Lucida is a 3D laser scanner custom built by Factum Arte with financial and logistical support from the Factum Foundation. Conceived and developed by artist and engineer Manuel Franquelo, it is the result of fourteen years of research into the high-resolution recording of the surface of paintings and relief of objects. The canvas’ colour was recorded with panoramic composite photography. The Lucida scanner is specifically designed to obtain 3D information from the surface of varnished canvases.
Factum Arte's Carlos Bayod recording the canvas’ surface area with the Lucida 3D Scanner.
The Lucida scanner is specifically designed to obtain 3D information from the surface of varnished canvases.
Processing the 3D and color data
The 3D and color information that was obtained has to be processed, using various types of software, to prepare final files for the reproduction of the canvas and frame.
Screenshots of the software's user interface during 3D model processing.
Following automatic processing, every single gap in the mesh is filled using a different type of 3D modeling software, in order to create a continuous 3D model.
Different screenshots of the software's user interface whilst completing the 3D model.
Multiple photos of the frame are then stitched together through special software and its data is converted into a 3D virtual model of the frame. The goal is to obtain a continuous mesh so it can be re-materialised with prototyping techniques such as 3D printing or CNC routing.
Shaded render of the frame's 3D model after processing.
The canvas' 3D data obtained with the Lucida 3D Scanner requires a different type of processing. The result is a greyscale depth map with a resolution of 100 microns (10,000 points/cm2) which can be appreciated as a shaded render.
Render of the canvas' 3D model after processing, general view.
Render of the canvas' 3D model after processing, details.
The canvas’ colour was recorded with panoramic composite photography. This technique consists of taking hundreds of small sized photographs of the surface of the painting which can be stitched together to create one single image with very high resolution. In this case, the resulting image has a resolution of about 450 ppi at a 1:1 scale. The canvas’ colour information has to then be registered onto the relief information obtained with the Lucida 3D Scanner.
Final image of the canvas, before colour correction.
Colour layer registered onto the relief layer.
Facsimile of the frame
High resolution 3D printing
The 3D model of the frame obtained with photogrammetry was processed and prepared for its re-materialization through stereo lithography 3D printing – an additive prototyping technique especially indicated to fabricating complex forms. While other fabrication methods were considered for this project, such as multi-axis routing, it finally was decided to use the enormous potential of high resolution 3D printing.
The model of the frame was 3D printed in prototyping material.
A nylon-based plastic material was used for this project, due to the specific characteristics of density and capacity to contain surface detail. The frame was 3D printed by the Belgian company Materialise in 11 parts, which were then glued together in Factum Arte’s workshop.
Detail of the 3D printed frame.
Hand-finishing to eliminate artifacts
Once the different sections were fixed together, it was necessary to retouch by hand the occasional artifacts generated by the digital process, either at the 3D editing phase or produced in the fabrication itself. The combination of digital technologies with traditional craft skills and a deep understanding of the material’s behavior are at the core of Factum Arte’s approach to art and conservation.
Factum Arte's Charlie Westgarth and Javier Barreno retouching the occasional artfacts in the 3D printed frame
Detail of the 3D printed frame’s surface after retouching.
Factum Arte’s Eva Segovia and David Carrillo applying a layer of clay prior to gilding.
Gilding
Factum Arte’s Eva Segovia and David Carrillo were in charge of the gilding. A layer of clay was applied to the 3D printed frame before gilding, in order to prepare the surface to receiving the gold leaf.
The manual work on the frame, from the surface-retouching to the gilding, was carried out by expert sculptors and gilders with many years of experience, using high resolution pictures of the object as a reference to reproduce the texture, color, shin and detail of the original.
The frame coated with clay in front of a picture of the original frame.
Factum Arte's David Carrillo applying the gold leaf on the frame.
Detail of a gilded element at the lower part of the frame.
Once the gold leaf was applied to the whole surface of the frame, the next step involved the darkening of the undersides of the decoration, as a restitution of the original aspect. Gilding the frame was a complex process which took the work of two artisans and various weeks to complete.
Restituting the original aspect of the frame was a complex process involving different techniques.
Factum Arte’s Eva Segovia and David Carrillo working on the frame’s surface.
Reinforcing structure
As an additional reinforcement of the frame’s strength, a 3 mm aluminum plate was laser-cut following the frame’s profile and fixed to the back. The plate was then colored and finished imitating the back of the frame, in order to blend both materials. The aluminum reinforcement will also be useful to facilitate hanging the facsimile on the wall without the need of touching the actual frame.
The aluminum plate was laser-cut following the frame’s profile, then glued to the back.
The reinforcement plate in the process of being fixed to the frame.
Facsimile of the canvas
Routing the relief onto polyurethane resin
The process of reproducing the canvas involved different techniques than those used for the frame. The relief of the canvas was recorded with the Lucida 3D Scanner, and the color was captured with high resolution composite photography. In order to restitute both types of information onto one single support it was necessary to carry out an experimental technique that would allow obtaining a flexible skin similar to canvas that contained the surface detail recorded with the 3D scanner. The color would then be printed digitally onto that canvas, in perfect registration.
Detail of the canvas’ relief routed on a resin plate.
The first step was therefore to mill the surface of the canvas as recorded with the 3D scanner onto a high density polyurethane resin plate, a material commonly used for prototyping. The milling was carried out by Francesco Cigognetti on one of Factum Arte's three-axis CNC routing machines. The height of the relief was increased 1.5 times the original, in order to keep the character of the texture through the whole process. The next step involved taking a mould of this routed surface, that will allow to “cast” a flexible skin with the same surface details contained in the milling.
A silicon mould was taken from the routed surface.
Several tests were carried out to find the best material properties of the canvas that would be used for the facsimile; appropriate thickness and flexibility and the capacity to reproduce texture detail were only a few of the parameters that had to be taken into account for this project.
One of the several tests that were carried out in the process of finding the best material.
Molding and transferring the relief onto linen
Once the material had been found, linen, the mould was used to cast the surface detail onto a thin section of it. In order to do that, a vacuum machine was used to make sure that all details in the texture were transferred to the skin. This technique, which is the evolution of previous methods used in Factum Arte, has been developed by Adam Lowe, Sebas Beyró and Rafa Rachewsky.
Fixing the linen onto the mould with vacuum mahine to transfer the surface detail.
Removing the linen with the relief information
The surface detail of the original canvas is contained in the linen (detail)
Printing color and fixing linen on the resin plate
The color was printed onto the linen using Factum Arte’s especially designed flatbed printer. This printer, based on the adaptation of a large size plotter, allows printing successive layers in perfect registration, which allows more control over the final result.
Detail of the print lit with raking light, in order to highlight the relation between color and surface.
Once the relief and color of the canvas was sorted out, it was necessary to provide the general topography or undulations that were present in the original canvas – as recorded by the scanner. This is a very important parameter in order to make sure the result is a convincing reproduction of the painting as three-dimensional object, not as a flat representation of an image.
Facsimile of the canvas and the frame together as one object (detail).
Detail of the facsimile: color, surface and shape were unified into one single object.
Facsimile of the canvas and the frame together as one object (detail).
