The bottom layer was paper and the top layer was the emulsion or binder and on the paper with two layers it might be collodion, egg-albumen or gelatine.
英
美
- 最底层是纸,而最顶层是乳胶或黏结剂;在两夹层之间的纸必须为胶棉、蛋白或是凝胶。