A new consolidation system for fragile ancient silk fabrics by fibroin with the support of ethylene glycol diglycidyl ether (EGDE) was developed in our group. To figure out the mechanism and the effect of EGDE in the system, aged silk fabrics treated with EGDE have been investigated in this paper. Silk fabrics were artificially aged in sodium hydroxide aqueous solution to simulate fragile ancient silk fabrics. The aged silk fabrics were treated with EGDE aqueous solution by spraying. The resultant silk fabrics were systematically investigated by tensile test, thermogravimetric analysis (TGA), thermal ageing resistance test, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), solid-state C-13 cross polarization/magic angle spinning nuclear magnet resonance (C-13 CP/MAS NMR) and amino acid analysis (AAA), etc. Results indicate that the breaking stress and strain of the treated silk fabrics increase more than four and two times, respectively. The maximum decomposition temperature of the treated silk fabrics is much higher than that of the aged silk fabrics. The treated silk fabrics exhibit a better thermal ageing resistance than the aged silk fabrics. Chemical interactions occurred between EGDE and silk fibroin molecules in silk fabrics. This work provides useful information for the protection of historic silk fabrics. (c) 2012 Elsevier Ltd. All rights reserved.