A unique process
Lumière
Technology's
multispectral process is unique.
This camera, which derives originally from the space industry, has been designed
for high definition scanning of all kinds of old and recent paintings.
A powerful beam of white light moves around the painting while the camera
scans it in high definition, thereby taking into account the rays reflected
by each pixel, illuminated by a light with a wavelength ranging between 380
nanometers (ultraviolet) and 1,050 nanometers (near infrared).
13 takes are required: 13 photos with unequalled accuracy, each with a definition of nearly 240 million pixels, before being able to virtually recreate the most accurate image ever of the Mona Lisa with a PC.
Click
here to read details about the multispectral camera technique
Read
scientific publications
Virtual
varnish removal
After having calculated the curve of the varnish spectrum, the latter was
digitally removed from these images in order to identify the original pigments
and virtually restore the portrait without its varnish.
The
materials of this famous masterpiece have faded over time and due to the conservation
conditions. The wooden support has retracted and generated a particular type
of crack.
The features of the binder, pigments and varnish have changed due to the ageing
process or their interaction with other materials. The loss of opacity of
the lead white is an example of pigment alteration. The binder also tends
to turn yellow.
As
all the painters in those days, Leonardo used a limited range of pigments
and mastic or rosin varnish.
Based on measures of recreated and artificially-aged period varnish, a “virtual”
varnish removal process of the painting has been carried out – an essential
prerequisite for restoring the “true colors” of the Mona Lisa.
Pigment
identification
All the pigments used in the days of Leonardo da Vinci are well-known.
Several are described in his famous Notes on painting.
Although “recipes” varied from one painter to another or even
from one country to another, the pigment base – i.e. the material elements
which make it up – is nearly always the same.
All these pigments – which usually come as powder – are then mixed
together into a binder in order to be applied with a paintbrush.
Until the 15th century, binders were made with eggs. This technique was referred
to as “a tempera”.
But for the Mona Lisa, Leonardo used a new oil-based technique from Holland.
This technique revolutionized painting – it is known as oil painting.
Leonardo probably used walnut oil.
We have combined all the pigments used in the days of Leonardo da Vinci into
one
single resolution target,
and for a better understanding and analysis of the mixtures and superimposed
pigments, each pigment has been divided into 6 versions (mixing and transparency).
The spectral data of each pigment is unique and enables faultless identification.
A piece of software analyzes the virtual samples of the Mona Lisa (once the
varnish has been virtually removed), and shows the composition of each mixture
or superimposed pigment. We thus know that the sky is made of a mixture of
lapis lazuli and lead white, that the skin is made of cinnabar/vermilion (mercuric
sulfide) and lead white, and that the shades of the skin are made of thin
transparent superimposed layers of umber (glaze technique).
Each mixture of pigments made by Leonardo da Vinci has thus been clearly identified,
and to confirm these results, the latter are matched up with the analyses
carried out using other techniques (X-ray microfluorescence, etc.).
Restoring the original colors
Certain
pigments deteriorate more than others. Lead white (also known as cerussite
or lead carbonate), for instance, tends to disappear and turn gray and dark.
It is unfortunately impossible to establish a general ageing rule for mixtures,
as they imply different chemical complexes.
Based on the Mona Lisa with its virtually removed varnish, a piece of software
maps all the mixtures of pigments (see
map) and replaces
them by new mixtures of pigments, thereby observing variations in brightness.
This task is long and tedious. The cracks, reflections and restorations have
been treated separately.
An
extensive analysis of the shots has made it possible to go even further. First
of all, it has revealed the layers of paint and undercoats covering the wooden
panel - poplar – on which it was painted. We can thus make out several
restorations, in particular a 2cm wide strip made of azurite covering the
entire width at the top of the painting.
It also suggested that the Mona Lisa held a fur coat on her lap which was
different from her main piece of clothing; the pictorial material of that
fur coat appears under infrared lights, which would explain the position of
her left hand attempting to hold it, as well as the sole visible retouch,
where Leonardo corrected the position of the fingers.
Click
here to discover "Mona Lisa's secrets"
Artistic reproduction
The Mona Lisa is priceless and almost impossible to restore due to the technique used by Leonardo da Vinci. The volumes and outlines have been retouched by adding fine colored glazes which gave it such wonderful chromatic subtlety. As the varnish is now mixed with the pigments, removing the varnish from the masterpiece – an essential prerequisite for restoring it – would remove all the colored glazes along with the varnish.
Through the multispectral shots of the Mona Lisa, which are both capable of accurately reproducing the masterpiece and revealing all the details of its history, it is now possible to rediscover the painting in all its chromatic glory.
The significant amount of pixels (240 million against 20 million for state-of-the-art cameras) makes it possible to obtain high definition enlargements with optimal sharpness and totally preserved colors. With our files, duplication capacities are unlimited. Printing may be carried out onto any type of medium: paper, canvas, hard material, cotton, silk, etc. with unequalled accuracy.
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