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  #1  
Old 17th February 2017, 11:03 AM
fotofundi fotofundi is offline
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Angry Alkali Stop Bath?

Does anyone have a formula for an Alkali Stop Bath? My source of ready-made has gone and I'm running out.
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  #2  
Old 17th February 2017, 04:02 PM
Lostlabours Lostlabours is offline
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Don't use an alkali stop bath, you run an extremely high risk of Dichroic fog and staining.

Use a normal stop bath, you can use it half strength if you want. Alkali fixers are buffered to work with an acid stop bat and the makers recommend using a normal stop bath for the reasons I've given.

With films a plain water stop is fine as long as there's a couple of rinses, it''s an either stop bath or water rinse recommendation given in data sheets by Kodak and Ilford.

It's particularly critical to use a good acid stop bath with Fibre based papers as an alkaline fixer doesn't neutralise the developer and you then get the staining etc.

Ian
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Old 18th February 2017, 11:22 AM
JOReynolds JOReynolds is offline
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Default Alkaline Stop Bath

Whoever suggested this? It goes against the acknowledged purpose of a stop bath - to stop development. I had never heard of an alkaline stop bath and found the concept baffling, so I googled and APUGed it, taking in Large Format Photography and a few other sites. I could find no proponents, only detractors, describing dichroic fog, blotchiness, fixing problems, several colours of highlight stain and suspected poor image stability, especially on FB paper.
It sounds to me like preying on the ignorant.
In an APUG post started by Beanzu on Oct 20, 2015, pawloski6132 contributed '...they probably don't know what they are talking about'.
As I write I have had a wonderful idea for an online money-spinner - farm-fresh cock's eggs, free P&P.
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Old 18th February 2017, 03:14 PM
Mike O'Pray Mike O'Pray is offline
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Yes, I must admit to never having seen a scientific explanation for alkali stop bath. From what I remember Peter Hogan's only explanation was along the lines of "why subject your film to an acid fixer that delivers a "shock" to it after coming out of an alkali developer.

I may be doing him an injustice but I cannot now check his text as the Peter Hogan site seems to be fault 403 "access forbidden"

I think there is still a belief in some quarters that in paper printing an alkali fixer is beneficial. Something to do with making it easier to rid the paper of fixer in the washing cycle than is the case with acid fixer?
Again I have no idea of the scientific pros and cons

Mike
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  #5  
Old Yesterday, 06:09 PM
fotofundi fotofundi is offline
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I have used Peter Hogan's alkali stop bath for years and have NEVER had an instance of dichoric fog or any other unpleasant side effect - that's about 200 rolls of film.
Prior to discovering Peter's product I used a one-shot very dilute acid stop bath, but was never convinced it did not have an adverse effect on pyro stain. A water rinse is an alternative, but not one I favour.
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Old Yesterday, 06:58 PM
Lostlabours Lostlabours is offline
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I can assure you that acid stop bath and normal fixers have NO effect on Pyro stain that was a myth that only originated with PMK,

You'll rarely get adverse affects with films and Hogan's alkali stop bath but you'll shorten your fixers life/capacity. It based on nothing he was a total fraud. His Prescysol was Sandy King's early Pyrocat HD and he copied Sandy King's original data sheet word for word with no changes at all. When challenge he had nothing to say.

There's a lot more but he's gone thank goodness.

Ian
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  #7  
Old Yesterday, 09:43 PM
fotofundi fotofundi is offline
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I didn't do any serious testing when swapping over from the dilute acid stop bath to Peter's alkali version, but as I was already using TF-3 alkali fixer the change seemed logical and the results were very satisfactory.
I suppose I could have looked into it more thoroughly, but when contemplating changes to successful procedures, I take the line that "if it 'aint broke, don't fix (!) it", and I never found any reason to doubt the product.
My film consumption has gone down drastically over the past couple of years and it is not worth spending a lot of time on this so I shall revert to my original diluted acid stop-bath. It might be interesting to see if I can detect any difference - but probably not.
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Old Yesterday, 10:25 PM
JOReynolds JOReynolds is offline
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Long ago, before my beard went grey, I shared in a shipment of two-part developer from the US - I forget the brand. Basically, it extended the H&D toe by suffusing the gelatine in Part A, a rich solution of developing agents. The film was then immersed in Part B, an alkali, in which density continued to build where there was little exposure - the shadows.
I evaluated the technique and found that the alkaline Part B was essential to the system: is that Hogan's intention?
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Old Yesterday, 11:11 PM
Mike O'Pray Mike O'Pray is offline
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For those really interested in the efficacy or otherwise of the Alkali Stop Bath, do a search for Prescysol on FADU. There were a number of threads on this in our early days when Peter Hogan was a FADU member and occasional contributor.

If I recall correctly a few proponents of Prescysol expressed an opinion( I put it no stronger than that) about what difference to the negative they found when using an acid stop bath.

Everybody needs to draw his own conclusion but if Peter gave a scientific explanation about why the alkali stop bath was either better or necessary then it wasn't very clear to me

There will of course always be believers and non believers
in the same way that debate( "debate" being a British understatement ) always arises on whether the Ilford film washing method of 5,10 and 20 inversions and dumps is good enough to give archival washing.

You pays your money and takes your choice as I think the saying goes

Mike
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