Fig. 2From: Study on microbubble of cellulose acetate microfilm of the Republic of China (AD 1912–1949) collected in the Second Historical Archives of ChinaOptical and SEM microscopy of microbubble disease of cellulose acetate microfilm: a Round ball-like shapes are more regular bubbles viewed with an optical microscope using transmitted light; b Irregular bubble shape viewed with an optical microscope using transmitted light; c SEM images of the microfilm without microbubbles; d SEM images of the microfilm with microbubblesBack to article page