Estratégias de reintegração cromática na pintura de Jorge Martins: no período de 1960 a 1980

The choice of materials for chromatic reintegrations in contemporary monochrome, nonvarnished, oil and acrylic paintings mark complex decision-making processes during an intervention. The particular characteristics of these paintings make them susceptible to abrasions, fingerprints and smudges. They take place mainly in the laterals due to the absence of frames, handling and transport. Being recent and non-varnished works, questions are raised related to the criteria and methodology of intervention, regarding the solubility of the pictorial layer, choice of materials, the compatibility and the color reintegration, which are hindered by optical phenomena like metamerism. This dissertation presents as a case study the technical and material analysis of five paintings by the Portuguese artist Jorge Martins, from 1960 to 1980. Nine oil and acrylic mock-ups were created, representing of the pictorial technique of Jorge Martins during this same timeline. In these models major damages such as abrasions, dirt stains and fingerprints were simulated. Subsequently, all models were submitted to technical photography, such as under visible, shallow angle, transmitted, ultraviolet and infrared light. They were also photographed and colorimetric measurements were taken using the hyperspectral imaging system (HIS) before and after an artificial aging of 500 hours according to ASTM D 4303-03, Standard Test Methods for Lightness of Colours used in Artist’s Materials. Of the nine mock-ups only six were aged, while the remaining three were used as a comparative examples and testing support for chromatic reintegration materials. During the chromatic reintegration tests, a variety of dry, aqueous and non-aqueous materials were tested on different substracts: the dry materials tested were Winsor and Newton® Watercolour Stick and Pan Pastel® Artist’ Pastels; the aqueous materials were tested with watercolours gouache paints, acrylics and methylcellulose and Tri-Funori® binders. The watercolour samples focused on the QoR® Watercolor, Mr. Graham® Artists Watercolour, Schmincke Horodam® Aquarell and Winsor & Newton® Artists’ Watercolours brands, and the gouache brands tested were Winsor & Newton® Designers Gouache and Royal Talens® and Guache Extra Fine Quality. The acrylics tested were Liquitex® Acrylic Markers Water Based, Winsor & Newton® Professional Acrylic, Lefranc & Bougeois® Acrylic FLASHE, Vallejo® Model Air Acryl Water Based and Interactive® Atelier Artists’ Acrylic. The samples prepared with methylcellulose and TriFunori® used Ferrario®, Winsor & Newton®, Sennelier® and Kremer® pigments. The non-aqueous materials focused on Kremer® color commercialization paints, urea aldehyde resin and the ethyl methacrylate and methylacrylate copolymer known as Laropal® A-81 and Paraloid® B-72 Chips; in the low molecular weight synthetic resins such as ketone MS2A® and aliphatic Regalrez® 1094: in synthetic polymers such as Paraloid® B-72 thermoplastic resin, in poly (vinyl-acetate) Gustav Berger® O.F. PVA Medium and the poly (2-ethyl-2-oxazoline) Aquazol® 200. The main pigments used in the tests performed on different substrates were Bright Red Cadmium (PR108), Cadmium Red (PR108) and Cadmium Red Deep (PR108) from Kremer® Pigment, Winsor & Newton®, Sennelier and Ferrario®. The selection of materials for the chromatic reintegration focused on the toxicity and quality of the visual properties that each one presented. The best results obtained were with Ferrario® and Winsor & Newton® pigments dispersed in Tri-Funori® aquous medium. Winsor & Newton® gouaches, the Designers Gouache, were also effective in some oil mock-ups lacunae