What is a protein paper base in photographic photos?

Protein photo refers to the photo printed by smearing egg white mixed photosensitizer on paper base, which is the most popular printing method after hard copy photo. Most of the photos and albums that appeared in the market before 1900 were photos of protein. Because of the low sensitivity, these photos could not be enlarged with the negative at that time and were printed directly from the negative, so the photo size was exactly the same as the original size. Protein photos are generally brown and warm colors, and the richness of image levels is much higher than that of hard copy photos. However, the stability of photos is not high, and they are easily affected by the preservation environment, and the high-profile parts are easy to change color.

Paper base: the support of photographic paper when developing photos. It is made of base paper after a certain surface treatment, and is used for coating photosensitive emulsion. In the past, barium sulfate was coated on the surface of base paper and then calendered, which was called barium base paper. At present, polyethylene film is widely used to coat titanium dioxide with a certain fineness on both sides of the base paper, which can not only partially cover some defects of the base paper, but also greatly reduce the water absorption and expansion of the image paper, especially greatly improve the quality of the color image paper. At present, plastic-coated paper base has mostly replaced barium-based paper base.