Study on the impregnation of Laropal A81 to consolidate the wood support in easel paintings

The following work is focused on the study of the suitability of the urea-aldehyde resin, commercially known as Laropal (R) A81, for consolidation treatments on deteriorated wood from panel paintings. The physicochemical properties of this resin, such as the low molecular weight, low viscosity in solution and, interestingly, the possibility to be dissolved in low-toxicity solvents, suggest that Laropal (R) A81 could penetrate well into the wood microstructure thus offering an alternative option to other resins which require the use of more harmful solvents. The behaviour of Laropal (R) A81 for the consolidation of deteriorated wood was compared to that of other two resins widely used as consolidants - Regalrez (R) 1126 and Paraloid (R) B72. Laropal (R) A81 was dissolved in Mostanol and in Dowanol PM, the Paraloid (R) B72 in butyl ethanoate and the Regalrez (R) in cyclohexane. ATR-FTIR was used for the assessment of resin retention and penetration depth in the wood, whereas FESEM images allowed us to evaluate the morphological changes undergone by the wood as a consequence of the application of the consolidation treatments. The changes in the gloss of the wood were also evaluated, which complemented the results obtained by the other two tests. According to the results obtained in this study, we argue that urea-aldehyde resin has good specificities (good retention and penetration depth) in order to be used as a consolidant for deteriorated wood in easel paintings.