I got a new (to me) 12x20 holder for my Folmer Schwing 12x20. It is not a Folmer Schwing film holder. I shaved down the ridge on one side to test it out.

I need to isolate some other issues with the camera to fully test the light-tightness of the holder. I am curious what best practices are with testing a new-to-you film holder.

I have some 10x12 xray film. I was thinking of loading some up and just letting the holders sit out in the sun for a bit. Then developing them to look for any leaks. This film is cheap so not a big deal. just time spent.