Although silver mirroring is more commonly seen in nitrate sheet films, it is also found in acetate negatives like this one. The most typical presentation of mirroring is around the edges of the film, as seen here. This mirroring was likely caused by air pollutants.

This 35mm nitrate strip demonstrates iridescent mirroring caused by silver corrosion. Iridescent mirroring in the highlights of an image is typical of nitrate film.

This nitrate negative shows iridescent mirroring in the boy’s face and collar, locations where the most available metallic silver is concentrated. Oxidation with an iridescent appearance is common in nitrate films, but it is not seen in acetate films. It is often accompanied by yellow or amber discoloration, as it is here, another visual manifestation of silver oxidation. Decay of the nitrate support likely contributed to the silver corrosion that caused this mirroring.

In this acetate negative, the poor quality paper masking and adhesive on the edges of the negative has caused mirroring underneath the masking.

This roll of 35mm acetate film was stored in a poor quality cardboard enclosure, which caused silver mirroring to develop on the roll. The outer wraps of the film, stored touching the inside of the cardboard enclosure, were the most severely affected by mirroring.

This detail of the 35mm film roll shows the extent of silver mirroring from the outermost wraps of film (seen on the left) to the innermost wraps (seen on the right). The silver mirroring becomes less intense and more focused on the edges of the film as the film is unwound, demonstrating that moisture and contaminants in the cardboard enclosure caused the mirroring on the outer wraps, while the edge mirroring found on the innermost wraps was caused by moisture and air pollutants.

Reference frames of 35mm from Tinting and Toning of Eastman Positive Motion Picture Film (Eastman Kodak, 1918) demonstrate blue metallic silver mirroring likely promoted by contaminants in the acidic paper that encloses the frames.