I thought I had solved the problem of the film and backing paper failing to separate for certain types of film. As a reminder the film comes through the slit with the backing paper and does not enter the film chamber in the Rondinax 60.
I thought applying extra pressure from the metal spoon in the lid was the answer to this problem as it is Andrés Cuervo’s problem in which the film comes out of the slit on top of the backing paper.
When I tried a Rollei Infrared film with tighter pressure from the spoon, it loaded fine. However, I realised a week or so later that the spool of film had been stored for several years and that the film itself coiled easily whereas when I first used film from that batch the film did not curl easily. So was I testing like with like? The answer was no.
I took the Rollei infrared film and an Ilford FP4 film and placed the backing paper and the end of film that loads first into the tank into a heavy book for a few weeks in order to flatten the films. Today I wound them back onto their reels. There was still some degree of curl in both films but when I tried to load them into the tank, they both failed to load, either jamming as they hit the ridge after they should have gone into the film chamber or coming out with the backing paper. With an open tank no amount of pressure on the top of the spool made any difference.
The answer must be that this type of failure to load must be related to how long the film has been spooled and to the properties of the film base. I must have had factory fresh Rollei film that takes some time to maintain a curl when spooled for the first time. It would seem that polyester film base might be particularly prone to wanting to stay flat, for want of a better term. However, the fact that flattened acetate-backed FP4 also failed to load would suggest that there may be a problem if really fresh film of that type is used. However, acetate may be less prone to wanting to stay flat since I have never had any problem with Ilford films.
A problem with film that had been in a camera for some time or had been wound backwards in some film backs was known about by Agfa and the instructions for using the tank (see Manual download for the Rondinax 60) include warnings like this one on page 21:
Partly exposed films which are in the camera for more than two weeks lose their curling quality. To regain this quality which is necessary for threading, the film must lie rolled up tightly for at least one day. Films from cassettes [film backs] with opposite winding must be rewound before (see p. 11)
In some roll film cameras the film is wound up in the opposite direction to the original winding. If these films are to be developed in the Rondinax 60 tank they must be rewound twice and kept tightly rolled up for at least a day. Caution! The film must be rewound twice so that the end of the film showing the word “exposed” points outwards again.
These instructions would have applied to acetate film. The question is: how long does it take for polyester film to gain or curliness its curliness? If my experience with Rollei film is anything to go back, some time in excess in several weeks for new film could be the answer. For the time taken to regain its curliness when spooled after partial flattening, I shall do further tests and report them here.
Clearly though, the physical property of ‘curliness’ and the maintenance of ‘curliness’ and ‘flatness’ when flattened or when spooled, respectively, is important for trouble-free use of a Rondinax 60.