If you put an exposed film in a Hasselbad and wind it on to the end, this is what happens.
What actually happens is that the film is jammed inside your Hasselblad and there’s no obvious way to retrieve it.
120 or roll film has a paper backing which is kept in place by a strip of tape at the leading edge of the film. When the film is loaded and wound on, the tape helps the film feed onto the take up spool and all is well. However, there’s no tape needed to keep the end of the film in place. But try to load an exposed film into a Hasselblad and within seconds you hit trouble. Without the tape, the film has no chance of feeding smoothly onto the take up spool. Instead it bunches up in the magazine. In this case, though it was hard to wind on (and yes I should have noticed but I was in a hurry!) it did seem to wind and take photos. But when the film got to the end it was impossible to unload.
The only solution to this I could find was the Hasselblad ‘jiggle’ as described in the manual as the correct action to take if the roll holder doesn’t click into place in the film magazine. Only this time it’s a reversing manoeuvre, and some considerable jiggling may be required. Though I’d advise taking it slowly and carefully.
There’s really no point in trying to take the magazine apart – I tried unscrewing various parts to no avail, but in the end the careful jiggling did the trick and after few hours of panic the roll holder came out.
Though the cost of a new back, or the repair charges were on my mind, what worried me most was how I was going to admit that I had made such a beginners’ mistake. I expressly forbade my friend from phoning his professional photographer and Hasselblad owner friend for advice for that reason.
Clearly, the best solution is prevention and it’s a mistake I will never make again.