Abstract. One hypothesis to explain the aesthetics of paintings is that it depends on the extent to which they mimic natural image statistics. In fact, paintings and natural scenes share several statistical image regularities but the colors of paintings seem generally more biased towards red than natural scenes. Is the particular option for colors in each painting, even if less naturalistic, critical for perceived beauty? Here we show that it is. In the experiments, 50 naïve observers, unfamiliar with the 10 paintings tested, could rotate the color gamut of the paintings and select the one producing the best subjective impression. The distributions of angles obtained are described by normal distributions with maxima deviating, on average, only 7 degrees from the original gamut orientation and full width at half maximum just above the threshold to perceive a chromatic change in the paintings. Crucially, for data pooled across observers and abstract paintings the maximum of the distribution was at zero degrees, i.e., the same as the original. This demonstrates that artists know what chromatic compositions match viewers' preferences and that the option for less naturalistic colors does not constraint the aesthetic value of paintings.3

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The ability to digitally remove the varnish layer during the pre-conservation diagnostic of a painting, without any chemical or physical intervention, could be an advantage because it enables the prediction of the outcome of the cleaning procedure of the protective layer and contributes to the treatment proposal. Two paintings from Adriano de Sousa Lopes were investigated by hyperspectral imaging in the visible range, before and after the varnish layer removal. The spectral reflectance was estimated in each case and its comparison used to assess the effect of the varnish layer removal. The simulated paintings with the old varnish layer were compared with those restored, with no varnish, by comparing the chromaticity coordinates and other chromatic descriptors. It was found that considering the effect of the varnish layer of each painting individually produces lower errors than considering the average of the varnish layer across paintings. It was also found that simulating the varnish layer removal without knowing the varnish transmittance produces limited results and that the errors are smaller if the chromatic content is assessed without considering lightness.

Laura Mora, Paolo Mora e Paul Philippot escreveram, por ocasião da primeira edição de Conservation des peintures murales, em 1975, que o tratteggio nunca tinha sido publicado em nenhuma revista técnica e que, apesar de ser praticado desde 1945, consideravam que ainda não tinha sido devidamente entendido, motivo pelo qual tentavam-no descrever detalhadamente. No inicio da segunda década do século XXI, várias são as situações, no caso concreto da reintegração cromática, em que persistem problemas de terminologia e alguma confusão acerca das técnicas de reintegração aplicadas em pintura, quer no discurso escrito, quer no discurso oral. Por esse motivo, o principal objectivo deste artigo é esclarecer a origem e os procedimentos originais de execução de algumas técnicas de reintegração cromática, as que normalmente se usam em pintura de cavalete em Portugal, tentando recorrer às fontes originais e a estudos específicos sobre o tema, bem como anotar particularidades na evolução das mesmas. O segundo propósito deste texto é facultar esta informação em língua portuguesa, algo inexistente até agora. Com base na interpretação das fontes bibliográficas concluiu-se que a mesma técnica pode ser praticada de modo diferente consoante a nacionalidade do conservador-restaurador, contribuindo para a evolução das técnicas existentes e para o aparecimento de outras.

This paper describes the application of 3D digital technology to support the rebuild of lost decorative elements of an historical frame. The frame belongs to an 18th century painting depicting the portrait of D. José, Prince of Brazil, displayed at the National Palace of Queluz, Portugal. The application of digital technologies has been planned from the very beginning in order to avoid the traditional use of silicone in the reproduction of missing elements. The photogrammetric 3D acquisition, a non-contact methodology, has been used to reduce the manipulation and hence prevent further degradation of the artistic object. Following the 3D modelling operation, new decorative elements were made using an additive printing technology. In the final phase of the work, the post-printing treatment was carried out, in which aqueous products were used. 3D modelling, in addition to facilitate the restoration treatment of the historic frame, can also be useful in the creation of a digital collection of decorative frame elements, i.e. a virtual database.