Elżbieta Jabłońska, Małgorzata Pronobis-Gajdzis & Tomasz Kozielec: The 11th-century Gniezno Codex Aureus.

From May to the end of November 2012, research and conservation were undertaken by the team of Cultural Heritage Institute, UMK in Toruń, on the 11th-century Gniezno Codex Aureus from the Archdiocese Archive in Gniezno. The codex was created by the Czech Benedictines in the second half of the 11th century. It was commissioned for the occasion of the coronation of the Bolesław II Śmiały, on the 25th December 1076. The book consists of 111 parchment leaves, richly illuminated, written with beautiful golden majuscule. It contains twenty full-page miniatures and is covered with a a gold tooled cover (which is not original, as that one was not preserved) on a very high artistic level, most likely by the 16th c. Poznan artist Erazm Kamyn. The codex is one of three still existing objects, being homogenous group characterised by the touch of probably the same scriptorium.

At the preliminary stages of assessment it was assumed that the main damages of the codex were physical-chemical changes of the materials (including parchment support), caused by the copper based pigments. It concerned all pages, and some of them were at the highest level of intensity, suffering from so-called “copper-green corrosion”.

As the object is one of the most precious Polish medieval codices, an object of extraordinary value not only for Polish but also international heritage, it was decided to do thorough research enabling the recognition of the technique as well as range and time of execution of intended historical inclusions layered on the original and last but no least the state of preservation of the codex. Yet the most important aim of the research was the examination of the chemical processes within the individual layers (gilding, paint layer, parchment support), in order to support plan of the conservation treatment methodology.

To get proper data of the identified material, an examination was undertaken using imaging remote sensing techniques as: UV reflectography, UV fluorescence, ViS, false infrared, NIR reflectography; physical-chemical research (XRF, FTIR spectroscopy, gas chromatography) and microbiological tests.

Non-invasive methods enable the documentation and interpretation of the optical effects related to the presence of various painting materials used in execution of the examined pages. With their help preliminary identification of pigments, binding media and varnishes was done as well as visualisation of the range of their presence within the paint layers. Physical-chemical research enabled identification of materials (support, gilding, pigments, and binding media).

Detailed analysis of all gathered data made it possible to establish the most likely history of the object related to the examined historical “additions” layered on the codex. Above all the state of preservation was established based on the analysis.

The research fully documented historical issues related to the time of execution of the object and with all historical layers added consciously and unconsciously, as well as the degree of degradation of the object materials, all of which is of great value, artistically, historically, scientifically, emotionally and educationally as well as for its uniqueness.

Finally there had to be undertaken an operation which would have made it possible to preserve above mentioned values and to stop the damaging processes. Conservation and restoration of this precious codex was carried out with full respect for the authenticity and integrity of the object. All interventions were made with maximum reverence to the original substance; all unnecessary operations were omitted. It was difficult and complicated to stop destructive reactions of copper pigments (green paints, gilded parts) which were damaging the degraded parchment support. The method developed gave great results. All interventions into the aesthetic side of the codex are distinguishable from the original and subordinated to it.

The crucial conservation attitude was that interference with the historical substance should be kept to a minimum and as well as the parallel treatment inhibiting destructive processes responsible for its degradation.