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RemJet (was Q: processing Kodachrome 25 color slide to get B&W?)



 
 
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  #1  
Old September 30th 03, 01:03 AM
David Foy
external usenet poster
 
Posts: n/a
Default RemJet (was Q: processing Kodachrome 25 color slide to get B&W?)

I'm puzzled. Again, I'm away from my bookshelf and can't provide a
reference, but I believe it is discussed L.F.A. Mason, "Photographic
Processing Chemistry." Mason was Ilford's chief scientist and published his
book in about 1960. Focal Press, of course.

According to Mason, these backings are added to films meant to be processed
on long-roll processors which have a large number of spools ("bobbins") over
which the film must pass. Complex processes like Kodachrome and early movie
films involve many immersions and the film has to be carried through a
relatively large number of tanks. The backing's main function appears to be
protecting the film from abrasion. Anti-static and anti-halation properties
are bonuses. I believe the original backing of the type was a layer of
colloidal silver, which was probably long ago replaced with something
cheaper.

So this raises a question: is the water jet situated somewhere far
downstream in the process? Does it achieve its purpose by washing off a
backing which has already been loosened by contact with alkaline developers?
If the backing is washed off at the outset, then Mason's explanation is
nonsense.

David Foy

"Richard Knoppow" wrote in message
nk.net...

wrote in message
...
I've heard that Kodachrome has a "backing" that has to be

removed in the processing. Is this what you are
talking about below and is this "backing" light tight? In

other words could you run 35mm Kodachrome
through a red window Bantam camera without paper backing?

Michael Scarpitti wrote:

Kodachrome films have a special
anti-halation backing that is NOT water-soluble (E-6 and

C-41 have
water-soluble antihalation layers).


Kodachrome has a backing of a material called Remjet. This
is a combination anti-halation and anti-static layer. Its
used on several types of motion picture film although Kodak
seems to be getting away from it in its newer MP films.
Remjet, as the name suggests, is removed by a high
pressure water jet at the entrance to the processing
machine. It can be removed manually by treating the film in
a mild carbonate solution and swabbing it off. If allowed to
go through a processing machine which does not have means
for removing it it becomes a sort of tar which is hard to
get out.
I don't know why this backing was used on Kodachrome. I
think Kodak would like to discontinue Kodachrome but it has
unique qualities which have kept it around for nearly
seventy years.
Home processing is not impossible but is impractical. The
Kodachrome process is very complex and some of the solutions
are very toxic. I have posted details of the process to the
group a couple of times in the past. I don't know if the
formulas for the current K-14 process are available anywhere
(I suspect they are) but the preceding K-12 formulas are
available in _Modern Photographic Processing_ Grant Haist
for those who are curious about it.
--

---
Richard Knoppow
Los Angeles, CA, USA





  #2  
Old September 30th 03, 02:35 AM
Robert Vervoordt
external usenet poster
 
Posts: n/a
Default RemJet (was Q: processing Kodachrome 25 color slide to get B&W?)

On Tue, 30 Sep 2003 00:03:20 GMT, "David Foy"
wrote:

I'm puzzled. Again, I'm away from my bookshelf and can't provide a
reference, but I believe it is discussed L.F.A. Mason, "Photographic
Processing Chemistry." Mason was Ilford's chief scientist and published his
book in about 1960. Focal Press, of course.

According to Mason, these backings are added to films meant to be processed
on long-roll processors which have a large number of spools ("bobbins") over
which the film must pass. Complex processes like Kodachrome and early movie
films involve many immersions and the film has to be carried through a
relatively large number of tanks. The backing's main function appears to be
protecting the film from abrasion. Anti-static and anti-halation properties
are bonuses. I believe the original backing of the type was a layer of
colloidal silver, which was probably long ago replaced with something
cheaper.


I don't think the above is true. I always heard that the backings and
silver layers were for anti halo effects.

So this raises a question: is the water jet situated somewhere far
downstream in the process?


I'm not sure what you mean by "dowmstream". Ordinarily, "downstream
would indicate further from the source and ,therefore, indicate
nearer the end of the process. If that is what you meant, then it is
"upstream".

Does it achieve its purpose by washing off a
backing which has already been loosened by contact with alkaline developers?


No.

If the backing is washed off at the outset, then Mason's explanation is
nonsense.


That is the case. It is a part of pre-development, in which the film
is put through a very alkaine pre-bath of wetting agents and
anti-foggants, This weakens the bond of the RemJet backing extremely
quickly. The bath is just 10 seconds in duration, so as to minimize
affecting the basic development characteristics of the film. It is
followed by a spray wash and soft scrub to the rear of the film base,
the REmJet area to remove the pre-bath and any remaining backing.

I heard this about Kodachrome, but read it in manuals describing the
machine processing of Eastman Color Negtive motion picture film.
Several long time laboratory men confirmed this about both processes.

RemJet removal precedes development.


David Foy

"Richard Knoppow" wrote in message
ink.net...

wrote in message
...
I've heard that Kodachrome has a "backing" that has to be

removed in the processing. Is this what you are
talking about below and is this "backing" light tight? In

other words could you run 35mm Kodachrome
through a red window Bantam camera without paper backing?

Michael Scarpitti wrote:

Kodachrome films have a special
anti-halation backing that is NOT water-soluble (E-6 and

C-41 have
water-soluble antihalation layers).


Kodachrome has a backing of a material called Remjet. This
is a combination anti-halation and anti-static layer. Its
used on several types of motion picture film although Kodak
seems to be getting away from it in its newer MP films.
Remjet, as the name suggests, is removed by a high
pressure water jet at the entrance to the processing
machine. It can be removed manually by treating the film in
a mild carbonate solution and swabbing it off. If allowed to
go through a processing machine which does not have means
for removing it it becomes a sort of tar which is hard to
get out.
I don't know why this backing was used on Kodachrome. I
think Kodak would like to discontinue Kodachrome but it has
unique qualities which have kept it around for nearly
seventy years.
Home processing is not impossible but is impractical. The
Kodachrome process is very complex and some of the solutions
are very toxic. I have posted details of the process to the
group a couple of times in the past. I don't know if the
formulas for the current K-14 process are available anywhere
(I suspect they are) but the preceding K-12 formulas are
available in _Modern Photographic Processing_ Grant Haist
for those who are curious about it.
--

---
Richard Knoppow
Los Angeles, CA, USA





Robert Vervoordt, MFA
  #3  
Old September 30th 03, 04:12 AM
James Robinson
external usenet poster
 
Posts: n/a
Default RemJet (was Q: processing Kodachrome 25 color slide to get B&W?)

Robert Vervoordt wrote:

I heard this about Kodachrome, but read it in manuals describing the
machine processing of Eastman Color Negtive motion picture film.
Several long time laboratory men confirmed this about both processes.

RemJet removal precedes development.


There's a document on Kodak's web site that describes the Kodachrome
processing steps. The very first step is the removal of the Remjet
backing. The description is as follows:

Backing Removal Solution - The alkaline backing removal solution
converts the rem-jet antihalation backing on the film base into a
water-soluble form. This backing is removed in the backing removal
wash.

Backing Removal Wash - This wash performs two functions:
1. It removes the backing removal solution from the film.
2. It completely removes the solubilized antihalation backing
from the base by a combination of water action and mechanical
buffing.

The next step is the first developer.
  #4  
Old September 30th 03, 04:13 AM
Ron Andrews
external usenet poster
 
Posts: n/a
Default RemJet (was Q: processing Kodachrome 25 color slide to get B&W?)

"David Foy" wrote in message
news:[email protected]
I'm puzzled. Again, I'm away from my bookshelf and can't provide a
reference, but I believe it is discussed L.F.A. Mason, "Photographic
Processing Chemistry." Mason was Ilford's chief scientist and published

his
book in about 1960. Focal Press, of course.

According to Mason, these backings are added to films meant to be

processed
on long-roll processors which have a large number of spools ("bobbins")

over
which the film must pass. Complex processes like Kodachrome and early

movie
films involve many immersions and the film has to be carried through a
relatively large number of tanks. The backing's main function appears to

be
protecting the film from abrasion. Anti-static and anti-halation

properties
are bonuses. I believe the original backing of the type was a layer of
colloidal silver, which was probably long ago replaced with something
cheaper.

So this raises a question: is the water jet situated somewhere far
downstream in the process? Does it achieve its purpose by washing off a
backing which has already been loosened by contact with alkaline

developers?
If the backing is washed off at the outset, then Mason's explanation is
nonsense.

David Foy

Rem Jet backing was historically referred to as an anti-halation
backing. It also:

protects the back side from abrasion BEFORE processing
reduces static by providing conductivity (contains carbon)
provides lubrication (like graphite, especially important for motion picture
film)
requires a special processing step for removal
makes a big mess if you put it in a process without this special step.

The rem jet removal is normally the first step in the process, so it doesn't
provide protection during processing. The binder is soluble in alkaline
solutions such as developers so it must be removed before the first
developer.




  #5  
Old September 30th 03, 05:15 AM
Norman Worth
external usenet poster
 
Posts: n/a
Default RemJet (was Q: processing Kodachrome 25 color slide to get B&W?)

The backing is removed early in the process, so it does not protect the film
back during processing. My understanding is that rem-jet is primarily an
antihalation coating. It is excellent for that purpose. The usual
formulation isn't very effective as an anti-static coating, although some
variations were tried for high-altitude and space recon film for a while.

BTW. the entire K-14 process has been published, and a summary, including
formulas, appeared in the February 1975 Dignan Newsletter.

"Robert Vervoordt" wrote in message
...
On Tue, 30 Sep 2003 00:03:20 GMT, "David Foy"
wrote:

I'm puzzled. Again, I'm away from my bookshelf and can't provide a
reference, but I believe it is discussed L.F.A. Mason, "Photographic
Processing Chemistry." Mason was Ilford's chief scientist and published

his
book in about 1960. Focal Press, of course.

According to Mason, these backings are added to films meant to be

processed
on long-roll processors which have a large number of spools ("bobbins")

over
which the film must pass. Complex processes like Kodachrome and early

movie
films involve many immersions and the film has to be carried through a
relatively large number of tanks. The backing's main function appears to

be
protecting the film from abrasion. Anti-static and anti-halation

properties
are bonuses. I believe the original backing of the type was a layer of
colloidal silver, which was probably long ago replaced with something
cheaper.


I don't think the above is true. I always heard that the backings and
silver layers were for anti halo effects.

So this raises a question: is the water jet situated somewhere far
downstream in the process?


I'm not sure what you mean by "dowmstream". Ordinarily, "downstream
would indicate further from the source and ,therefore, indicate
nearer the end of the process. If that is what you meant, then it is
"upstream".

Does it achieve its purpose by washing off a
backing which has already been loosened by contact with alkaline

developers?

No.

If the backing is washed off at the outset, then Mason's explanation is
nonsense.


That is the case. It is a part of pre-development, in which the film
is put through a very alkaine pre-bath of wetting agents and
anti-foggants, This weakens the bond of the RemJet backing extremely
quickly. The bath is just 10 seconds in duration, so as to minimize
affecting the basic development characteristics of the film. It is
followed by a spray wash and soft scrub to the rear of the film base,
the REmJet area to remove the pre-bath and any remaining backing.

I heard this about Kodachrome, but read it in manuals describing the
machine processing of Eastman Color Negtive motion picture film.
Several long time laboratory men confirmed this about both processes.

RemJet removal precedes development.


David Foy

"Richard Knoppow" wrote in message
ink.net...

wrote in message
...
I've heard that Kodachrome has a "backing" that has to be
removed in the processing. Is this what you are
talking about below and is this "backing" light tight? In
other words could you run 35mm Kodachrome
through a red window Bantam camera without paper backing?

Michael Scarpitti wrote:

Kodachrome films have a special
anti-halation backing that is NOT water-soluble (E-6 and
C-41 have
water-soluble antihalation layers).

Kodachrome has a backing of a material called Remjet. This
is a combination anti-halation and anti-static layer. Its
used on several types of motion picture film although Kodak
seems to be getting away from it in its newer MP films.
Remjet, as the name suggests, is removed by a high
pressure water jet at the entrance to the processing
machine. It can be removed manually by treating the film in
a mild carbonate solution and swabbing it off. If allowed to
go through a processing machine which does not have means
for removing it it becomes a sort of tar which is hard to
get out.
I don't know why this backing was used on Kodachrome. I
think Kodak would like to discontinue Kodachrome but it has
unique qualities which have kept it around for nearly
seventy years.
Home processing is not impossible but is impractical. The
Kodachrome process is very complex and some of the solutions
are very toxic. I have posted details of the process to the
group a couple of times in the past. I don't know if the
formulas for the current K-14 process are available anywhere
(I suspect they are) but the preceding K-12 formulas are
available in _Modern Photographic Processing_ Grant Haist
for those who are curious about it.
--

---
Richard Knoppow
Los Angeles, CA, USA





Robert Vervoordt, MFA



 




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