[pure-silver] Re: Pre-soaking film
- From: Snoopy <snoopy@xxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Fri, 30 Apr 2010 11:30:40 +0200
Dear Richard and John etc.
thats what the guys at Ilford told us.
Richard: I did not speak for Kodak, sorry, this was Ilford at the time
(1981 i.e. nearly 30 years ago, gosh, I _am_ getting on a bit :-)) and
later (late Nineties) I heard the same from the film folks at AGFA...and
recently (2009) from another member of the AGFA Photo Club.
Also: I meant b/w film! Colour is again different of course! But The
initial discussion was about b/w ? I did mention that I also pre-soak
colour?
I distinctly remember old FP4 and HP5 35mm films being VERY thick, they
had a really "spongy" feel to them when they were wet. B/W Films have
gotten LOTS LOTS thinner since then. They feel very different to the
point of me somtimes wondering if there is any emulsion on them at all...
Richard: in no way did I intend to slander Kodaks quality! I am sorry if
you took it that way. I admit freely that I know sweet FA about Kodals
manufacturing but more about Ilford (see above) and even more of AGFA
(because we hadf a lot of contact to the film testing guys from via our
Photo Club).
I recall the times when Kodak "professional" film came with a slip of
paper in the box which would tstate the correct "measured" sensitivity
in DIN/ASA as opposed to the blurb on the outside box.
But I would expect larger format films to have a thicker base layer ?
From your and Johns posting it sounds like:
Sheet film is thickest, then 35mm and 120 is thinnest ?
Should 120 not be thicker than 35mm to ensure it lies flat in the camera?
I am puzzled...
Love,
Snoopy
Richard Knoppow wrote:
>
> ----- Original Message ----- From: "Snoopy" <snoopy@xxxxxxxxxxxxxxx>
> To: <pure-silver@xxxxxxxxxxxxx>
> Sent: Friday, April 30, 2010 1:28 AM
> Subject: [pure-silver] Re: Pre-soaking film
>
>
>> Dear Harry et. al.,
>>
>> harry kalish wrote:
>>
>>> I think their rep at a trade show mentioned that they had started to
>>> incorporate a wetting agent in their film---roll film only?, I'm not
>>> sure.
>>>
>>
>> it almost certainly is not "roll film only". Roll film and 35mm come
>> from the same rolls of very wide (several meters wide) coated emulsion.
>> Roll films are then cut out of the center strip because the emulsion
>> there is more "evenly coated" over a larger area.
>>
>> 35mm are cut from the remaining "edges" of the rolls: as they are
>> narrower again the emulsion thickness (i.e. the gelatin layer) is fairly
>> even over the area of the film, but there is more variation between the
>> rolls, as the big rolls gelatin gets thicker towards the outside.
>>
>> This added to the "story" that roll films are "professional" films, with
>> a higher consistency. Hence I would bet, that also the 35mm films had
>> the wetting agent: they come off the same roll.
>>
>> When I was a student in England our PhotoSoc once visited Ilfords plant.
>> The scale of things was awesome. They made millions of films every MONTH
>> and used massive saws (all in the dark) to cut up these huge rolls. Hell
>> of a noise too.
>>
>> Love,
>> Snoopy
>>
> Roll film and 35mm film do NOT come from the same master rolls, for
> one thing the support is different. 35mm film is coated on a support
> which is much thicker than roll film and sheet film on support which is
> thicker yet.
> I don't know where you got the idea that the emulsion thicknes varies
> across the roll. In fact, emulsion thickness is very well regulated
> throughout. Most films do not have a single coating anyway. There is
> always a substrate to get the emulsion to stick to the support and
> usually more than one emulsion coating. Most films have an anti-abrasion
> coating on top of the emulsion. Some color films have twelve or more
> emulsion coatings. These must all be coated with extreme uniformity.
> I don't know what Ilford consideres "professional" vs: something
> else. Kodak makes all films to a single standard. Since one of Kodak's
> largest customers is the motion picture industry, which requires an
> extreme standard of uniformity, it has learned to meet that standard and
> applies the same technology to other kinds of films.
> All films have various sorts of additives in them some of which are
> proprietary. These probably include wetting agents. Most motion picture
> stocks are intended for machine processing and I am not certain if a
> wetting agent is desireable in them.
> Some wetting agents, notably the ones used in Photo Flo are not
> suitable for direct use in developers but there are others that are.
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk@xxxxxxxxxxxxx
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