Nanocellulose has been recently proposed as a novel consolidant for historical papers. Its use for painting canvas consolidation, however, remains unexplored. Here, we show for the first time how different nanocelluloses, namely mechanically isolated cellulose nanofibrils (CNF), carboxymethylated cellulose nanofibrils (CCNF) and cellulose nanocrystals (CNC), act as a bio-based alternative to synthetic resins and other conventional canvas consolidants. Importantly, we demonstrate that compared to some traditional consolidants, all tested nanocelluloses provided reinforcement in the adequate elongation regime. CCNF showed the best consolidation per added weight; however, it had to be handled at very low solids content compared to other nanocelluloses, exposing canvases to larger water volumes. CNC reinforced the least per added weight but could be used in more concentrated suspensions, giving the strongest consolidation after an equivalent number of coatings. CNF performed between CNC and CCNF. All nanocelluloses showed better consolidation than lining with synthetic adhesive (Beva 371) and linen canvas in the elongation region of interest.

The aim of this study was to develop new, sustainable treatments for the consolidation and conservation of canvas of modern and contemporary art. Because of the diversity of painting types, two product groups which have polar and nonpolar character were developed. The treatment should be applicable to the back side of the canvas. The deacidification agents are sub-µm-particles of calcium carbonate or magnesium oxide which are dispersed in water or heptane. The polar components are hydroxyethyl methyl cellulose and nanocrystalline cellulose which are biopolymers derived from renewable raw materials. The nonpolar products were obtained by the silylation of the raw materials and allow the solubility in nonpolar solvents as heptane. Each product was applied to highly degraded, acidic model cotton canvas as well as canvas from real paintings. The application of these products showed a good increase of breaking force at a low increase of the mass of the canvas and also had only slight optical changes of the canvas. The deacidification of canvasses is a good preventive measure and can protect canvasses from future damage by acidity. The deacidification agents showed an increase of pH from acidic to alkaline after the treatment and a deposition of an alkaline reserve.

Recent developments in paper and canvas conservation have seen the introduction of nanocellulose (NC) as a compatible treatment for the consolidation of historical cellulosic artifacts and manuscripts. However, as part of the assessment of these new materials for canvas consolidation, the adhesion of the consolidation treatment (which takes place between the applied material and the substrate) has not yet been evaluated, and as a result, it is poorly understood by both the scientific and conservation communities. After evaluating the potential of NC treatments for the consolidation of cotton painting canvas, we investigate a route to promote the interaction between the existing canvas and the nanocellulose treatment, which is in our case made of cellulose nanofibrils (CNF). This was carried out by introducing a cationic polymer, polyamidoamine-epichlorohydrin (PAAE), as an intermediate layer between the canvas and the CNF. The morphological, chemical, and mechanical evaluation of the canvas samples at different relative humidity (RH) levels demonstrated how the adhesion of the added PAAE layer is a dominant factor in the consolidation process. Improvement in the coating of canvas single fibers by the CNF, higher adhesion energy between the canvas fibers and the CNF treatment, and finally overall stronger canvas reinforcement were observed following the introduction of PAAE. However, an increase in mechanical response to moisture sorption and desorption was also observed for the PAAE-treated canvases. Overall, this study shows the complexity of such systems and, as such, the relevance of using a multiscale approach for their assessment.

The aim of this work was to evaluate the use of novel nanocellulose-based consolidants for modern easel paintings as a possible alternative to lining and to the use of common adhesives. Two dispersions of consolidants were tested: nanofibrillated (CNF) and nanocrystalline cellulose (CNC). A model cotton canvas was used to evaluate the effect of these consolidants following treatment by the nanocellulose-based formulations. The surface appearance of the canvases was assessed before and after treatment using colorimetry and scanning electron microscopy (SEM). Additionally, the characterisation of the mechanical properties of the samples was performed using tensile testing and dynamic mechanical analysis (DMA-RH) at controlled relative humidity (RH) (3 RH cycles, 20-60-20% RH at 25 °C) before and after treatment. Finally, colour changes undergone by the samples upon accelerated ageing were measured by colorimetry. Taking into account the individual outcomes of each of these tests, it was possible to evaluate the merits and limitations of the use of nanocellulose treatments for the consolidation of modern painting canvases.