Brittle paper was deacidified and then subjected to accelerated aging. The deterioration of this paper was followed by measuring folding endurance with a modified M.I.T. Folding Endurance Tester which measures folding endurance at the standard fold angle of 135° and at smaller fold angles, 90° and 45°. Results show that the deacidification teatment was benefical, having slowed down the degradation process. The smaller fold angle was useful in following the degradation or the very brittle paper.