Other New Data Revealed

The contribution of the fluorescent tube is not limited to the spectacular aspect of the discoveries described above. Under this light there also appears a great quantity of information (Table 9.1), whereas with a UV lamp, photography with filters, special films and image manipulation, the data are gathered separately. These normal methods have in no way been replaced. However, the fluorescent tube enables one to make remarkable observations such as those below, with great visual comfort, in contrast to the Wood lamp which makes one's eyes tired very quickly:

• The concentration of red pigments can be evaluated as soon as the painting is lit.

• The paints and natural oxidations can easily be distinguished from each other.

• The rock support is differentiated from all the other elements stuck to its surface.

• Patinas can be seen and precisely determined.

• Surfaces of calcite can easily be localized where they were previously unknown.

• Algae and lichens are clearly delimited, while others which were unsuspected betray their presence.

• Bones and bone fragments which were unknown on the walls and floor have been revealed.

• Imperceptible fossils, enclosed in the rocky support, are indisputably located.

• Flints (identical) display their different aspects (colours, patina, breakages, etc.).

• Blows struck against the wall and surfaces that were destroyed in ancient times can be identified.

• Historical scratches can be recognized as such.

Table 9.1 Colours perceived on the walls of Gouy according to the lighting used

Wall

Without special lighting

By the light of the vegetal fluorescent tube

By black (ultraviolet) light (320 400 nm)

General colour: the white of the chalk, which is mixed with a whole range of greys, with no possibility of attribution

Dominant: purplish pink attenuated by a rapid adaptation of the eye (example: the white, although pinkish, is perceived as white)

Dominant: dark blue

Other colours: grey, light blue, purple blue, purple

PAINTING no. 1

Oxidation Patina

Calcite

Grey mixed in with all the other greys

Grey (among other greys)

Indiscernible

Red (can be seen with the naked eye), identical to painting 5

Red (can be seen with the naked eye), identical to painting 4

Grey

Indiscernible Indiscernible

Bone fragment Discernible with difficulty

Historical scratches Fossil Flint

Lichen

Discernible with difficulty Grey, white

Grey (various, up to black) Grey (among other greys)

Dark red Red

Orangey red Intense red

Intense red

Yellow Grey

Active concretion: white

Dried-up concretion:

grey

Yellow White

Grey (among other greys)

Grey (among other greys) Barely perceptible grey Intensive luminescence saturated pink red

Grey

Grey

Dark grey found on all the walls Fluorescent white (luminous)

Dark yellow Shining white

Yellow (typical) White

Grey, blue, brown, Brown, black black, yellow

Very bright light green Grey (among other greys)

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