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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 ref lectance 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. Resumo A capacidade de remover digitalmente a camada de verniz na fase de diagnóstico de uma pintura, sem qualquer intervenção química ou física, poderá ser uma vantagem, pois permite prever o resultado do procedimento de limpeza da camada de proteção e auxiliar a proposta de tratamento. Duas pinturas de Adriano de Sousa Lopes foram investigadas por imagiografia hiperespectral na zona da luz visível, antes e após a remoção da camada de verniz. A ref lectância espectral foi estimada em cada caso e sua comparação utilizada para avaliar o efeito da remoção da camada de verniz. As pinturas simuladas com a camada de verniz envelhecida foram comparadas com a intervencionada, sem verniz, comparando as coordenadas cromáticas e outros descritores cromáticos. Verificou-se que considerando o efeito da camada de verniz de cada pintura individualmente obtêm-se erros mais baixos do que considerando a média da camada de verniz das duas pinturas. Verificou-se também que simular a remoção da camada de verniz sem saber a transmitância do verniz original produz resultados limitados e que os erros são menores se o conteúdo cromático for obtido sem considerar a luminosidade.

Chromatic changes in paintings of Adriano de Sousa Lopes after the removal of aged varnish