From: rspeirs@javelin.sim.es.com (Ron Speirs)
Subject: Re: B&W film reversal processing
Keywords: black and white slides from B&W/color films.
Organization: Evans & Sutherland Computer Corporation
Date: Thu, 16 Apr 1992 18:09:34 GMT

In article <107@metran.UUCP> jay@metran.UUCP (Jay Ts) writes:
>
>After receiving a few very helpful replies on my request for info on Kodak's
>T-max 100 Direct Positive Film Developing Outfit, I went ahead and tried it.
>Thanks, everyone, who replied.  The results were great.
>
>I found out that the price ($25-30 in local stores) was not so bad considering
>the kit can be used for 12 rolls of film (you have to buy fixer separately,
>but that's not so bad).
>
>Now on to greater topics!  I need some more help.  After processing a roll
>of T-max 100, I started thinking ... the chemistry should work not only on
>any black & white negative film, but on color films as well (to yield B&W
>transparencies).  There are three possibilities that I am mostly interested
>in.  They are:
>
Whenever you go out of the photographic "mainstream", you need to understand
exactly what is going on with your processes.  Here is a description of the
B&W reversal process:

The First Developer is an ordinary high contrast negative developer with
a silver solvent (sodium thiocyanate or sodium thiosulfate) added to remove
just enough silver to produce clear highlights.  The film is then rinsed.
The Bleach (potassium dichromate with sulfuric acid or sodium bisulfate)
removes the *developed* negative image from the film, but leaves the
*undeveloped* silver halides intact.  The film is rinsed again and goes
to a Clearing Bath (sodium sulfite) which neutralizes any remaining bleach.
Then the film is either exposed to light or fogged chemically, which
makes the remaining undeveloped silver halides developable.  A Second
Developer, essentially the same as the first developer without the
halide solvent, develops the remaining "positive" image.  This is followed
by a standard fixer, wash, dry.  

Since the image is composed of the same kind of developed silver halides
as in a negative-processed film, I would expect the grain and archival
properties to be the same.  

>	1)  Reversal processing of Tech Pan for pictorial photograpy.  I want
>	    to see how sharp 35mm slides can be.  The Kodak Kit has directions
>	    for use with Tech Pan and high-contrast (copy) work.  Is it
>	    possible to substitute Technidol for the kit's first developer
>	    to achieve normal contrast (contrast index of ~0.6)?

This would certainly be worth a try.  You would need to add some Sodium
Thiocyanate (~2 g/L) as a silver solvent to produce clear highlights.  The
following is a formula for pictorial Tech Pan processing from about 1979:

	Water			800 mL
	Metol (or Elon, or
	 p-methyl aminophenol sulfate)
				  4 g
	Sodium Sulfite Anhy.	 25 g
	Hydroquinone		  5 g
	Benzotriazole 0.2%	 15 mL
	Potassium Bromide	  2 g
	Sodium Carbonate Monoh.	 30 g
	Sodium Thiocyanate	  2 g
	Potassium Iodide 0.1%	  1 mL
	Water to make		  1 L

This is for the First Developer.  The remainder of the step in the kit
should be OK.  Be sure to test and bracket widely to find the E.I.
>
>	2)  B&W reversal processing of Kodachrome 200.  Why?  Because shooting
>	    T-max 100 at EI 50 makes it really slow.  I am guessing that
>	    it is possible to shoot Kodachrome 200 at EI 200 and get good
>	    black & white slides from it.  And maybe something weird and
>	    interesting will happen.  Actually, I suppose it would be more
>	    sensible to request info on reversal processing T-max 400 and
>	    T-max P3200.

Beware!  Something weird and interesting might happen:  Kodachrome film is
really a "Black-and-white" film.  It has three B&W layers separated by color
filters, and the dyes are introduced onto the film during the separate
development of each color layer.  BUT, Kodachrome also has a coating on the
BACK of the film like is found on color negative motion picture films.  In
commercial Kodachrome processing, this layer (colloidal carbon black) is
removed prior to development.  You wouldn't be able to do this, and so the
particles from this backing would contaminate your solutions.  If, after you
have used your processing kit to exhaustion, you want to try this experiment,
go ahead.  You will be able to remove the remainder of the carbon backing 
by rubbing the film gently under running water.  You should get a reversed
B&W image.
>
>	3)  B&W reversal processing of E-6 films.  Well, why not -- C-41
>	    films too!

I think this is like spending dimes to get nickels.  E-6 films can be
reversed to get a positive B&W image, but remember that there isn't as much
silver in color films (since it is only a "catalyst" to get the dyes to
form) as there is in B&W films (where silver IS the image).  Since E-6
films are so much more expensive, why?  With C-41 colorneg films, the orange
masking might get in the way.  However, I don't know if the orange masking
is built into the film or if it is created during development.  I'll have
to experiment.
>
>I have been thinking that there is some general method to use to convert
>from "normal" processing, i.e., "6 minutes in D-76 for a negative with
>contrast index of 0.6" to the reversal method.  But right now there are
>too many loose ends for me to figure it out.  For example, I don't know
>how active the 1st reversal developer is compared to Tmax or D-76 developers.
>It would help me greatly to know what kind of contrast index (and overall
>density) the 1st reversal developer achieves.  Would it by any chance be
>the same as if I shot T-max 100 at EI 50 and processed it to be a "pulled"
>negative?  I don't think so, but then I'm confused ... I guess I need a
>little reversal processing theory to start out from.
>
>If anyone has suggestions, please, please offer them to me; you will save me
>a LOT of experimentation!  I prefer email to save net bandwidth, but I suppose
>posting has positive side effects as well.

A call to Kodak's information line informed me that the Kodak Direct Positive
Panchromatic Film 5246 (which had an ISO of 80) was discontinued in 1989.
There are three faster reversal films (Plus-X, Tri-X and 4-X- reversal), but
they are only available in 16 mm.  The person at Kodak said that T-Max 400
could be developed in the T-Max reversal kit, but NOT T-Max 3200.

Ron Speirs, Evans & Sutherland Computer Corp., Salt Lake City, Utah