pre-wet before film developing question
Peter Groepper
and in others "pre-wet recommended". What shall I believe?
My film (4x5) is Ilford Delta 100, my developer either Perceptol or
ID-11 and my process is JOBO Multitank on a motorized roller, speedwise
similar to the JOBO processor.
I have understood, that pre-wetting lengthens the dev. time, while
rotation processing compensates for that lengthening, thus leading back
to the original dev. times. But I have no idea, what is better.
Thanks for any hints.
Peter Groepper
John Hicks
<pgro...@estec.esa.nl> wrote:
>In some brochures or leaflets I find "generally no pre-wet recommended"
>and in others "pre-wet recommended". What shall I believe?
Ilford specifically recommends against prewet, while Jobo otoh
recommends prewet. Here's my experience....
For rollfilm in a Jobo I've found that a prewet is a must; it
prevents airbells that I can't get rid of any other way no matter how
much tank-banging and inversion agitation before putting the tank on
the machine.
For sheetfilm, though, that I process in Unicolor print drums, I
don't use an prewet and have no problems with HP5+, the Deltas or APX
100.
As far as the actual process goes, a one-minute prewet will have no
significant effect on speed or contrast, while otoh a long prewet,
such as the five minutes Jobo recommends, will have a significant
effect and you'd need to adjust development accordingly.
It's not consistent; some films gain a little speed and contrast
while others lose a little.
---
John Hicks
John's Camera Shop
L. J. Powell
> In some brochures or leaflets I find "generally no pre-wet recommended"
> and in others "pre-wet recommended". What shall I believe?
>
> My film (4x5) is Ilford Delta 100, my developer either Perceptol or
> ID-11 and my process is JOBO Multitank on a motorized roller, speedwise
> similar to the JOBO processor.
>
> I have understood, that pre-wetting lengthens the dev. time, while
> rotation processing compensates for that lengthening, thus leading back
> to the original dev. times. But I have no idea, what is better.
>
> Thanks for any hints.
>
> Peter Groepper
There are no absolute answers here. I always prewet, and I am satisfied
with the results I get. Others don't prewet, and they are happy with their
results.
I use HC110, dilution B. I have done a lot of Zone System testing to
arrive at my exposure index and development time, taking into account the
prewet. I suspect that attempting to use a prewet cycle without doing
testing to understand how it affects the rest of the process could cause
unsatisfactory results.
The theory behind prewetting is that it brings the film up to the
temperature of the development solution, thereby assuring consistency in
the development process. It also is supposed to prewet the emulsion and
prevent so that the developer can start to work right away - this should
shorten the development time.
An agument against prewetting is that the emulsion becomes saturated with
water, and it therefore takes longer for the developer to penetrate in and
affect the lower layers.
--
=-=-=-=-=-=-=-=-=-=-=
Louie J. Powell, APSA
Glenville, NY USA
http://www.geocities.com/Paris/Maison/7881/
"Entia non sunt multiplicanda praeter necessitatem"
=-=-=-=-=-=-=-=-=-=-=
Phil Herring
> In some brochures or leaflets I find "generally no pre-wet recommended"
> and in others "pre-wet recommended". What shall I believe?
Try both. Use whichever gives you the results that you prefer.
> I have understood, that pre-wetting lengthens the dev. time, while
> rotation processing compensates for that lengthening, thus leading back
> to the original dev. times. But I have no idea, what is better.
A pre-wet will usually shorten development time. The theory behind
pre-wetting is that the dry film emulsion is slightly waxy, and initially
repels water; as a result, the first uptake of water into the dry emulsion
tends to be uneven and slow. This can result in some parts of the emulsion
being exposed to development for significantly longer than others,
producing uneven development. A water pre-soak fixes this by ensuring that
the whole emulsion is wetted by the developer for the same time.
Pre-wetting is mostly only required for older-style, thick-emulsion films,
or very short development times, or highly dilute developers; most modern
film/developer combinations don't need it.
John Hicks
in the emulsion surface therefore using a prewet can cause unevenness
that otherwise wouldn't occur.
In practice, I've used a prerinse with Ilford films with no bad
effects.
Bill Troop
Phil Herring wrote:
...
> A pre-wet will usually shorten development time. The theory behind
> pre-wetting is that the dry film emulsion is slightly waxy, and initially
> repels water; as a result, the first uptake of water into the dry emulsion
> tends to be uneven and slow. This can result in some parts of the emulsion
> being exposed to development for significantly longer than others,
> producing uneven development. A water pre-soak fixes this by ensuring that
> the whole emulsion is wetted by the developer for the same time.
There could be more to it than that. Years ago, prewetting was advised as a
way
to increase speed slightly. The theory was that soluble bromide in the film
(included
as an antifoggant) would be removed; hence less restraint during development.
Later, when so many accelerators were added to emulsions, most emulsion
designers felt that prewetting would cause speed loss by leaching out some of
the accelerators. I do know that Silvia Zawadzki (formulator of XTOL and
co-designer of some of the T-Max films) is adamantly opposed to pre-wetting
except where a particular film-size/developing process makes it mandatory.
F.C.Trevor Gale
I have observed on many colour films that the anti-halation layer comes
off nicely when one pre-washes for 1 minute at the same temperature as
the developer process (e.g. C-41, 1 minute prewash at 38degs C). I find
that it certainly avoids the otherwise extra pollution of the developer:
therefore I now pre-wash *all* colour developing that I do.
On the other hand, with black-and-white films where I use a one-shot
developer most of the time, I clearly don't worry about pollution of the
developer. I find that for most mono developing, a pre-wash doesn't
really give me an advantage. Caveat: this works provided that reasonably
normal or longer developing times are used. If you use a concentrated
developer for any reason and end up with very short dev times, then
perhaps a pre-wash does aid the smooth take-up of the developer into the
emulsion.
The prewash from Kodak colour films pours out of the tank quite a dark
green!
Regards, Trevor Gale.
Clyde Davidson
recommend prewetting any Ilford film except when using Jobo. Then you
should do the full 5 minute prewet that will completely wash away the
wetting agent.
Clyde
xxxx
I know that bye pre-washing for a time (1 min) will decrease contrast in
B&W film and provide a more even developing. The reason is that the
developer will affect the bright areas (dark area of the negative)
quicker then the dark areas (clearer areas).
randy zack
I have follwed this suggestin wit no problems. Randy
John Hicks
>In article <3679D0...@xs4all.nl>, tg...@xs4all.nl says...
>
>I know that bye pre-washing for a time (1 min) will decrease contrast in
>B&W film and provide a more even developing.
Phil Davis published a test a while back in which he found that some
films gain a little speed and contrast, some lose speed and contrast
and some were unaffected. The longer the prerinse the greater the
Keith McCarron
in grain size through silver migration. Some manufacturers do not recommend
pre-wetting film because of this possibility.
xxxx wrote in message ...
>In article <3679D0...@xs4all.nl>, tg...@xs4all.nl says...
>
>> > > A pre-wet will usually shorten development time. The theory behind
>> > > pre-wetting is that the dry film emulsion is slightly waxy, and
initially
>> > > repels water; as a result, the first uptake of water into the dry
emulsion
>> > > tends to be uneven and slow. This can result in some parts of the
emulsion
>> > > being exposed to development for significantly longer than others,
>> > > producing uneven development. A water pre-soak fixes this by ensuring
that
>> > > the whole emulsion is wetted by the developer for the same time.
etc, etc.
bubba
something about prewetting paper. I drum process my color paper and
initially I would automatically prewet the paper before introducing the
developer. There was nothing very scientific about it - I used tap water in
generous amounts to make sure the emulsion was wet. My theory was that I was
using a very minimal amount of developer in the drum for economic reasons,
and I wanted to be sure I didn't leave any under developed areas on the
print due to the surface tension of the liquid developer on the dry paper.
One day I accidentally forgot the prewet step and I noticed that I got back
a noticeably smaller amount of used developer than the fresh developer I put
in. It dawned on me that the emulsion was absorbing some developer and
holding it like a sponge. I was never able to notice that with my prewet
technique because I didn't bother to measure the water going in or coming
out.
My conclusion now is to follow the manufacturer's instructions. If no prewet
is recommended, I don't prewet on the theory that their formulations are
geared to their instructions. If they are counting on the emulsion absorbing
a certain amount of developer rather than plain water it must be that they
require a certain concentration of developer in the emulsion to work
properly. Introducing water instead of developer would serve to dilute the
chemistry inside the emulsion where it counts most.
Since then, I've stopped prewetting my paper and instead I use a tiny bit
larger amount of developer in the drum than the bare minimum the
manufacturer suggests. This may cost me a few cents more per print, but I've
noticed deeper, more vibrant colors since I stopped prewetting.
Tom
F.C.Trevor Gale wrote in message <3679D0...@xs4all.nl>...
>Bill Troop wrote:
>>
>> Phil Herring wrote:
>> ...
>>
>> > A pre-wet will usually shorten development time. The theory behind
>> > pre-wetting is that the dry film emulsion is slightly waxy, and
initially
>> > repels water; as a result, the first uptake of water into the dry
emulsion
>> > tends to be uneven and slow. This can result in some parts of the
emulsion
>> > being exposed to development for significantly longer than others,
>> > producing uneven development. A water pre-soak fixes this by ensuring
that
>> > the whole emulsion is wetted by the developer for the same time.
>>
Mel1wood1
In article <75tlki$a8r$1...@lore.eur.sprynet.com>, "bubba" <tomc...@sprynet.com>
writes:
>Since then, I've stopped prewetting my paper and instead I use a tiny bit
>larger amount of developer in the drum than the bare minimum the
>manufacturer suggests. This may cost me a few cents more per print, but I've
>noticed deeper, more vibrant colors since I stopped prewetting.
>
I thought that prewetting color paper was in fact to bring the drum and paper
up to temperature... which in effect will give you the correct time for
development.
mel
bubba
critical than with paper. 1/4 degree F accuracy is specified in some
situations. There again, I would follow the manufacturer's instructions. If
prewetting is part of the official procedure - do it! If not, I don't.
Tom
Mel1wood1 wrote in message <19981226092002...@ngol05.aol.com>...