Evaluation of chia and flax mucilages as consolidants of paint films and as hydrogels used in the cleaning of canvases reverses: first results

Abstract

In the field of conservation of cultural heritage, animal glues, synthetic resins, and some polysaccharides are used to consolidate pictorial layers. Meanwhile, in order to clean the obverse and the reverse of paintings, organic solvents and aqueous systems are sometimes employed in the form of gels. In this work, vegetable mucilages have been tested for both applications. This research has been carried out in several phases. Firstly, mucilages were extracted from flax and chia seeds. The efficacy of the obtained products was tested on two kinds of mock-ups. As consolidantes, the mucilages were applied on a board with a film of powdery tempera painting. In the case of their use as cleaning gels, two linen cloths were prepared: one with animal glue and the other with gacha, an adhesive used in the Mediterranean Basin. In the last step, the efficacy and safety of the treatments were determined through microscopic observations and FTIR-ATR measurements. Colour and gloss characterisation were also performed in the consolidated pictorial layers. According to the first results shown in this work, flax mucilage can consolidate disintegrated layers of rabbit-skin glue tempera producing minimum colour and gloss changes, whereas chia mucilage has less efficacy to consolidate the tempera. Regarding the efficacy of mucilages as hydrogels, both have shown promising results. With these first results, future work will focus on the study of the long-term behaviour of vegetable mucilages through accelerated artificial ageing and on laying the foundations for their use in other conservation treatments, such as the cleaning of pictorial layers.