How do I know if it was old chemicals that did not produce images on the film strip or something else?

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My chemicals are about four years old and maybe used about six times. They have been stored inside my home, 75° F, and in a cabinet. Chemicals are in glass beer growlers with tight lids. This is the first time I developed and have no images. I am thinking it’s that my chemicals are now expired but I am unsure if this is what it looks like if they are bad. Or it’s a result of something else. Are are No images, no sign of any frames. And yes, the film seems to be thinner than normal. Can someone tell me if this is the result of bad chems? They also haven’t been used in a year

What is DX film encoding?

What is “DX encoding” of roll film, such as 135 format film used in 35mm cameras? How does it work? When was it introduced? Is there anything else I need to know about using DX encoded film in a camera that can read the encoding? How about in a camera that can not read the encoding? For that matter, how can I tell if my film camera can read DX encoded film?

Will the quality of Kodachrome 40 Super 8 film developed in 1980 be affected by age?

I have a Kodachrome 40 Super 8 film cassette, which was exposed, developed and viewed using a projector in 1980. I have not tried to view/project the film recently. However, the film in the cassette now looks completely grey, with no sign of any developed images. Is this type of cine film affected by aging after it has been developed?