Having used Rondinax 60 tanks on and off for 120/620 films for over 55 years without ever having a problem, I was shocked when I tried to develop a modern Rollei Infrared film a few weeks ago. As I pulled the backing roll the film came out as well instead of rolling into the light-tight chamber inside the tank! Because I had no darkroom nor changing bag with me I had to start feeding the film into the chamber with the lid off, losing a few exposures at the end of the film in the process.
I think there are two differences for this failure: firstly, the backing paper feels a little thinner than on FP4+; secondly, the film itself does not curl. I can only assume that whereas a ‘normal’ roll comes to the point at which the film bends inwards into the container, the non-curly film just carries straight on with the backing roll to the outside. The seemingly thinner paper backing roll seems cannot help.
Incidentally, but no help in the present discussion, the non-curling property makes the film very easy to scan.
I looked up the specifications of the Rollei infrared film. It is polyester with a non-curling coating, 0.1 mm thick. By contrast Ilford FP4+ and HP5+ rollfilms are acetate 0.11 mm thick, with no mention of a non-curling coating. Kodak rollfilms appear to be slightly thinner than Ilford (0.09 mm), again with an acetate base and no mention of a non-curling coating.
It would be interesting to know if other Rollei 120 films with a similar base will not separate in a Rondinax 60. It is also important that other people know if there are problems with specific 120-size films. Please comment below so we can draw up a list of those films where a changing bag is essential if a Rondinax 60 or Kent 20 is being used.
And yes, I did note the irony that the only film that has failed was made by what remains of Agfa-Gevaert for what remains of the Rollei brand. An Agfa film not suitable for an Agfa tank. I bet they did not spot that problem coming in the 1930s. A few old Agfa employees will be spinning in their graves.