The brown stain which can sometimes be observed on 8x10 film is caused by lack of neutralization of the paste in the film’s trap. In our other integral film formats (600, SX-70, Spectra, i-Type), there is a strip of woven trap material at the top of the film. This contains a sponge-like material with an acidic pH. As the alkaline paste found inside the developer pods spreads across the photo, the acid in the trap material neutralizes any excess paste that reaches the top of the frame, preventing overdevelopment of the image.
Polaroid Originals’ 8x10 integral format film does not contain any neutralizing agent in the trap end. Original Polaroid 8x10 format was a peel-apart film, so any paste that was caught in the trap area would have been peeled off with the film negative and discarded. Integral film does not have this attribute; the positive and negative sheet stay together, and the alkaline paste stays in close proximity to the negative and sheet.
Due to this structural difference, some of the alkaline paste from the trap end area will slowly migrate onto the photo area. This reaction visually manifests itself as a brown stain at the top end of the photo.
Currently we do not have a built-in solution for this problem, but we do have two recommendations that will help prevent or reduce this issue:
1. Once your image has fully developed, cut away the trap area of the frame and discard it
2. Once your image has fully developed, squeeze any excess paste out of the trap area. This is a messy and delicate task, however, and because the paste is highly alkaline, you should make sure to wear protective gloves to prevent the paste from coming into contact with your skin. If you get any paste on your skin, you should rinse the area immediately with cold running water. If irritation persists, you should seek medical advice as soon as possible.