Museum artifacts made of polyurethane ester foam are frequently affected by conservation issues mainly related to the loss of their mechanical properties. Modification of mechanical properties often leads to structure crumbling and in some cases to the loss of the entire artifact. A previous study evaluated the possibility to reinforce new flexible industrial polyurethane ester foam with aminoalkylalkoxysilane (AAAS) based treatments. In this paper AAAS are applied on artificially degraded polyurethane ester foam to investigate the possibility to reinforce already degraded objects. Two AAAS, the 3-Aminopropylmethyldiethoxysilane and the N-(2-Aminoethyl)-3-aminopropylmethyldimethoxysilane have been tested. AAAS solutions at different concentrations have been used to apply the monomers on the foam samples by immersion. Mechanical properties have been studied by Compression Force Deflection Test, which shows that after AAAS treatment the resistance of the foam to compression improves and the cell collapse is prevented. The color of the samples, before and after consolidation, has been monitored to assess the impact of the treatment on the visual aspect of the foam. AAAS distribution in the thickness of the samples has been investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Silicon Magic angle spinning nuclear magnetic resonance (29Si MAS NMR) has been used to confirm AAAS polymerization and to evaluate its average polymer chain length. 29Si MAS NMR has also been used to investigate the behavior of AAAS polymers in time by analyzing four years old reinforced samples. The results highlighted the stability of the poly-AAAS chains after four years of natural aging.