Scientific Investigation of the Paintings from the Agarbiciu (Cluj County) Wooden Church

The investigation of the painting materials (pigments, binders and varnish) of Agarbiciu wooden church painted walls was done by employing both nondestructive (XRF and reflection FTIR spectroscopy for pigments) and destructive methods (FTIR spectroscopy and GC-MS spectrometry for pigments and binders). The digital restoration of the interior of the wooden church was done using the physical-chemical composition of the painting layer, a metadata set that describes the timeline, detailed photographic documentation and the 3D scanned interior of the church.


Introduction
The Agarbiciu village wooden church ( Figure 1 The shingle covered roof is guarded by a bell tower which rises high above the narthex and its crest is flanked by four small turrets. The painting was made by Dimitrie Ispas from Gilau village in two stages: the altar and the nave in 1801 and the narthex and southern facade in 1818. This arises from the two inscriptions above the vestibule separating the nave and narthex. In the first inscription you can find the year of painting, the names of the painter, archpriest, priest (bishop name missing) and the ruling emperor name accompanied with various felicitations and whishing and the fact that the expenses were covered by the villagers ( Figure 2).
In the second inscription, you can find the year of the painting, the names of the painter, archbishop, archpriest, priest, curators, the name of the ruling  Physical-chemical investigations [7]- [13] of the materials used by Dumitru Ispas to paint this church were made to support conservation and restoration activities.

Nondestructive Analyses
Nondestructive analyses were performed using portable devices by approaching them to the paintings (

Destructive Analyses
The samples for destructive analyses were collected from areas where the painting layer was exfoliated in order to not damage the painting. LGC Standards GmbH, Wesel, Germany) and mixed in an ultrasonic bath two stage of 10 min each maintained at 40˚C. The sample was centrifuged 5 minutes at 3000 rot/min and then 2 µ of supernatant was injected. In this condition the fatty acids were derivatized to ethyl ester fatty acids.

Destructive FTIR Spectroscopy
The investigations were performed for each colour from the following paintings.                Table 1.

Destructive Analyses
The quantitative determination of monocarboxylic fatty acids allows us to distinguish between different triglycerides sources (drying oil or egg) on the basis of characteristic parameters [15]. The ability to recognize original materials is due to the use of molecular markers that remain stable under aging.
The unsaturated fatty acids were excluded from classification rules based on previous works [15] that found the ratios of these compounds are dependent on drying and aging conditions. We used the C16:0/C18:0 ratios to discriminate between binders. This parameter is fairly constant for each binder and independent of both the aging treatment and the pigment. This ratio (P/S) can be used to identify each type of drying oil and is not affected by the aging process [14] [15] [16].
From Table 1, it results in that the ratio P/S is 1.02 for Sample 1 and 1.06 for Sample 2. According to the P/S value, it was suggested that linseed oil was used as Figure 19. FTIR absorption spectra of red painting material.   The compounds detection from the "Agarbiciu green and binder" sample,

Digital Conservation
The digital preservation of the interior of the wooden church will be done using a metadata set that describes the timeline, the physic-chemical composition of the painting layer, detailed photographic documentation and the 3D scanned interior of the church.
Following the physicochemical analyzes described in the previous chapter, the pigments used for the church interior painting can be obtained in the laboratory ( Figure 22) digitized and preserved digitally.

C. Măruțoiu et al.
The pigments can be used in the process of digital repainting to eliminate the effect of time and other factors that degraded the painting layer ( Figure 23).
The documentation of the current preservation status of the painting layer has been made digitally using detailed photography within the visible spectrum, IR and UV (Figure 24).
The photographic documentation was done using professional equipment (Canon 5DSLR, 50 Mpx), the light was measured and recorded every 10 minutes using a spectrometer (Sekonic C7000) (Figure 25), the acquired data will be archived together with the pictures in RAW file format.       The interior has been 3D scanned using the Z + F Imager 5010× terrestrial scanner, the model obtained has a resolution of 1 mm, the texture has also been acquired and mapped to the 3D scanned model (Figure 29).
At the following link, all in-situ investigations for the Agârbiciu Wood church can be observed at the following link (https://youtu.be/RDzLErFioX0).
Using multiple digitization techniques, the most important elements of the Agarbiciu wood church was acquired and preserved digitally. The availability of these data to the general public is problematic for now because of the large file size, which will be solved by using cloud solutions and improved bandwidth internet connections. At the following address: (https://recap360.autodesk.com/project/49d75f68e850401c91c965e942de3ea6) a possible distribution of 3D scenes can be viewed. The digitization and digital preservation of the wooden churches is particularly important given that their current deteriorating status and the fact that in most cases these belong to small communities without sufficient financial resources to restore and preserve them.

Disclosure
Măruțoiu Constantin and Bratu Ioan are co-first authors.