Anti halation dye - where does it go?

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rme615f - 07 Mar 2006 14:02 GMT

I use barry Thorntons 2 bath developer, more for convenience than any
other reason. I normally don't pre wash, but out of curiosity did, last
time I developed a film. Man, the dye came out like squid ink!

Normally, without a pre wash, the first bath comes out a bit pink, but
runs clean after a few fillings of the tank (inversion washing), but
nothing like the blue inky stuff that came out after the pre wash.
Where does it all go when you don't pre wash?!

TIA

Stu

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UC - 07 Mar 2006 14:10 GMT

THINK!

> I use barry Thorntons 2 bath developer, more for convenience than any
> other reason. I normally don't pre wash, but out of curiosity did, last
[quoted text clipped - 8 lines]
>
> Stu

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Nicholas O. Lindan - 07 Mar 2006 15:20 GMT

> Where does [all the film dye go] it all go when you don't pre wash?!

The chemicals in the developer change it from colored to clear, as
indicator stop bath changes yellow to purple. I find the Agfa dye
turns blue again if used developer gets on paper towels. It doesn't
seem to be a pH thing, adding acetic acid to the used developer produced
no color change back to blue.

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Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
Fstop timer - http://www.nolindan.com/da/fstop/index.htm

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dan.c.quinn@att.net - 07 Mar 2006 23:16 GMT

> > Where does ... it all go when you don't pre wash?!
>
> It doesn't seem to be a pH thing, ...

Quite likely it is a redox reaction. The developing agents
and sulfite in developers are reducing agents. The paper
towel likely has nothing to do with the blue. Rather it
is exposure to the oxygen in the air.
Sulfite alone may clear the blue. To a small sample add
a few grains and see what happens. Also test a sample with
a little unused developer. Dan

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David Nebenzahl - 08 Mar 2006 01:00 GMT

dan.c.quinn@att.net spake thus:

>>> Where does ... it all go when you don't pre wash?!
>>
[quoted text clipped - 3 lines]
> a few grains and see what happens. Also test a sample with
> a little unused developer.

Sulfite *does* clear it. I know because I dump my prewash (dark blue)
into a jar, then later dump my hypo-clearing agent (sodium sulfite) into
the same jar, which instantly clears the color. It's actually quite
dramatic.

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Do we call the country Italia? Is its capital Roma?
Were previous Olympics held in Moskva, Muenchen or Athine?
Do we call it the "Shroud of Torino"?

No!

So learn to speak English already and call it Turin.

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rme615f - 09 Mar 2006 18:04 GMT

> > Where does [all the film dye go] it all go when you don't pre wash?!
>
[quoted text clipped - 9 lines]
> To reply, remove spaces: n o lindan at ix . netcom . com
> Fstop timer - http://www.nolindan.com/da/fstop/index.htm

Thanks for the explanation. I'm glad UC wasn't the only reply!

Stu

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Nicholas O. Lindan - 10 Mar 2006 14:41 GMT

dan.c.qu...@att.net wrote:

> Quite likely it is a redox reaction. ... The paper
> towel likely has nothing to do with the blue. Rather it
> is exposure to the oxygen in the air.

Ah ha! I was wondering what could be in paper towels to cause
such a reaction ...

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Richard Knoppow - 11 Mar 2006 02:53 GMT

> dan.c.qu...@att.net wrote:
>
[quoted text clipped - 5 lines]
> cause
> such a reaction ...

Regeneration of the anti-halation dye is one of the
symptoms of "vinegar syndrome", the symptoms of the
decomposition of acetate film base. I am not sure what is
exuded by the decomposing base but it re-colors the dye,
which remains in the anti-curl coating in its colorless
state after processing.
It may be oxygen but I suspect there may be something
else in the towels which promotes the reaction. After all,
the film backing is exposed to the air all the time.

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---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com

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Nicholas O. Lindan - 11 Mar 2006 12:42 GMT

> It may be oxygen [that causes developer-dissolved anti-
> halation dye to colorize] but I suspect there may be something
> else in the towels which promotes the reaction. After all,
> the film backing is exposed to the air all the time.

Sulfite clears the color - which points to redox. Rodinal comes
out dark purple from the dye, contains no sulfite but
is a strong reducing agent - which points away from simple
redox.

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Richard Knoppow - 11 Mar 2006 13:41 GMT

>> It may be oxygen [that causes developer-dissolved
>> anti-
[quoted text clipped - 9 lines]
> is a strong reducing agent - which points away from simple
> redox.

Contrary to popular belief Rodinal does contain sulfite,
check the ingredients on the bottle or in the MSDS.
I think the color of Rodinal after processing is not from
the anti-halation dye. The dye is decolorized by sulfite in
either developer or fixer.

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---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com

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dan.c.quinn@att.net - 12 Mar 2006 00:39 GMT

> Sulfite clears the color - which points to redox. Rodinal comes
> out dark purple from the dye, contains no sulfite but is a strong
> reducing agent - which points away from simple redox.
>
> Nicholas O. Lindan, Cleveland, Ohio

Two variables may be in play; ph and redox potentials. As we
all know ph plays a part in silver reduction. In a nut shell, reducing
agent redox potentials are such as to reduce silver halides in an
alkalin solution.
To investigate further I'd first make a distilled water extraction
of the antihalation material and go from there.
The matter may be more complex. The color-no-color
phenomenon may occure at more than two points with shifts in
the ph-redox mix. I've seen enough from the posts so far to feel
sure that some redox type reactions do take place. So, just what
is that is-blue-on-pre-wash substance Mr. Knoppow? Dan

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