When WW2 era 120 medium formal film gets too hot in the sun, can it melt, or become soft and sticky, and clump together? It might seem like an odd question, but there is some background to it. My granddad on my father's side got drafted into the Wehrmacht, and took a camera with him when he served on the western front in France. When he came back, there were no photos. The reason that was always passed along in my family was that he left his backpack with all the film in the sun, the film clumped together, and he had to toss out the entire mess. Of course as a kid I believed this, but now I am a chemist with some experience in polymer chemistry, and I know that some polymers can do that, but most won't. It's also awfully convenient for all the pictures from a war to disappear, that the photographer would rather not want to have been in. As a side, note, my granddad later became a prisoner of war in Russia. At that stage he had left his camera at home, which is why I now have it. When he came home, people in the village did not recognize him, and the doctor gave him weeks to live. Thanks to the tender loving care of my grandma, he pulled through, and happily lived well into his 80s. My grandparents lived in the same house with us. I knew my granddad well, and we had a very good relationship. In all my life, I never heard him say one bad word about the Russians. He nearly starved to death, but so did the Russians after the war, and my granddad said they shared whatever little they had with the prisoners. Whenever questions came up about what the Germans had done, my granddad ended the discussion with one short sentence: "Germans are bad!" But be that all as it may, at this stage I am really only interested in the material properties of vintage film. Will it melt in the sun or not? Does anybody have experience with this, and does my granddad's story check out?