Jobo Expert Drums and film washing

[percepts]

I am curious about something and have a two part question.

The first part is:

do some films have dyes on the reverse side of the film or are they always on the emulsion side?

The second part is only applicable if there are dyes on the reverse side of the film:

How do Jobo expert drums manage to wash out the dyes on the reverse side of the film when the film is inserted in the tube so that the reverse side of the film is against the side of the tube? Or have I misunderstood about the way expert drums are loaded and work?

 

[jstraw]

Answer to the first, yes...most, if not all. When I presoak my FP4+ and dump the water, all that purply-green stuff is the anti-halation dye that's come off...not that it ever all comes of in my presoak.

 

[percepts]

well thats what I thought, especially HP5.

As I told you in another thread, developing sheet film back to back stops washing out of those dyes.

So in a Jobo expert drum, is the back of film sheets right up against the wall of the tube or are they just flexed across the width of the tube so that both sides of the film are open to being covered in chemicals?

 

[Neal]

Dear Percepts,

1) I may be wrong but I am under the impression that the anti-halation layer is between the emulsion and the backing.

2) Something else I might be wrong about but I thought I'd read that the cylinders in the expert drums are not true cylinders. That they are slightly larger in diamter in the middle than at the ends.

Neal Wydra

 

[jstraw]

Ok, we need PE or someone that really knows the straight dope to talk about anti-halation dyes.

 

[jp80874]

From Ilford's PDF on FP5+, "HP5 Plus sheet film is coated on 0.180mm/7-mil
polyester base with an anti-halation backing which clears during development."

The holes in my 3010 (4x5) and 3005 (8x10) drums are visually out of round to let the chemicals flow behind. Larger sizes have ribs to keep the film away from the wall. For 7x17 I do two sheets in combined tanks or tank and extension, 2830 and 2560. Larger than this, a 3063 paper drum for up to a 20x24 sheet, the ribs make marks if film is used. Jobo Ann Arbor made an insert of mesh that solved this problem. That was lost in the change over. Many of us would like to find one of those. In my case it would allow developing three sheets of 7x17 at once instead of two.

Hope that helps.

John Powers

 

[percepts]

no we don't. I just sacrificed a sheet of hp5 which confirms what I thought was the case. HP5 has dyes on the non emulsion side of the film. Whether they are anti-halation or something else is not really relevant in the context of this thread.

So now I need to know how it is that expert drums are able to wash those dyes out when the film is against the tube wall.

Neal says the tubes are an irregular shape which kind of suggests that chemicals can get behind the film.

Anyone with more info on this and how it really works in the expert drum system.

 

[percepts]

thanks John,

our posts crossed in the ether.

So my concerns were not founded. Good news.

 

[Jim Noel]

Since the tubes in the Expert drums are not cylinders, but barrel shapes, the liquids are able to get behind the films and remove the anti-halation layers very effectively. If there is a problem with them remaining, try adding about 1 TBS of sodium sulfite to the pre-wash and it should take care of the situation. The small amount of sulfite remaining after dumping the pre-wash has never caused me aproblem since it is only a preservative.