The back wall of the church was totally covered in fresco painting until, at an undetermined point, the placement of a wooden altarpiece led to its chipping.
The fragments that resisted this intervention featured great cohesion of the plaster and optimal adherence to their support, except in a small area.
The painting, according to the technicians who performed the recovery, represent six musical angels, three on each side of the central niche, with the upper ones playing wind instruments and the two at the bottom playing the harp.
One can not tell whom the upper angels are turning their eyes to because of the destruction of the closure area. The lateral walls of the niche are covered by decorative painting of a reduced palette upon a black background, and an underlying decoration may also be perceived.
The opening of two "windows" on the lateral walls of the niche allowed achieving greater cohesion of plaster with a significant layer of colour, executed in fresco, similar to the angels. Above is a tempera painting.
In order to protect the layer of colour of weaker cohesion, dry cleaning sponges were used, with particular emphasis in the white and colour areas, to enhance the contrast with the black background. Yet, the underlying painting was wet-cleaned.
Not all gaps were filled with lime mortar and low grain sand, because traces of an earlier fresco had been discovered, in the upper right side.
This finding is consistent with the existence of an earlier back wall.
A chromatic reintegration was performed, with watercolour, of the small gaps in the colour layer of the most recent paint layer, however the underlying paint coating did not undergo such process.
The joints of the back wall received a mortar of lime and sand of medium grain size in the filling in depth, after which they were subject to levelling by applying the same mortar used on the sidewalls. Then, two whitewashes were applied to erase the traces of dark blue plastic paint, concluding with a whitewash lightly pigmented with earth.
The wet-cleansing of the back wall of the chancel was conducted before proceeding to its consolidation.
The fresco painting was executed on thin fresh plaster, and the colour palette limited to white, black, earth colours and blue background. Probably the artist did not enjoy the intensity of the blue, so he applied it a thin layer of lime water, in order to smooth it.
The lateral walls of the chancel were, at first, white whitewashed, followed by a layer of lime mortar and sand of low grain size in the joints, in order to mitigate the huge gap between the filling with cement, but without any concern for total levelling.
Then, a first whitewash of lime pigment, similar to the one used in the back wall of the niche, and a second whitewash of pigmented lime were applied only in the stones.