Does anyone know how long an image will stay on an exposed but undeveloped wet plate? A museum curator nearby asked me if I could develop some of their exposed but un developed collection of glass plate negatives. The images are at least fifty years old.. I suggested that they not be processed. I have processed verichrome pan film that had a thirty year span between exposure and development. I was quite surprised that the image would keep so long. Are there commercial labs that process glass plate negatives? Assuming that they were shot by the same photographer and his methods had some consistency, They could develop one, and adjust development time, then do another. I told her I would look into it. This is the best place that I know of to get that info. thanks bk