AFAIK, the research at IPI never determined what the change in
KRST was. Do you know of later research on this?  There was
speculation that there was some sulfide or polysulfide as an impurity
in one of the ingredients. Kodak claims that the formula and method of
manufacture have not changed.
    Full toning with any sulfide or polysulfide toner, or with
Selenium or Gold toners, provides full image protection. The problem
with KRST is when it is used as long recommended, i.e., at a 1:20
dilution. According to personal communication with Dr. Nishimura, KRST
will provide full protection when used at a dilution of no greater
than 1:9 and for not less than 3 minutes at 68F.
     Polysulfide toner made so that the concentrate has high order
polysulfides, will tone all densities uniformly so will provide full
protection even when only partial toning is done. Kodak Brown toner,
at the recommended dilution works fine as does T-8. Agfa Viradon
should work as well. Kodak Polytoner, and the older version of
Viradon, were combinations of Polysulfide and Selenium. These toners
provide full protection but were less desirable for microfilm because
they affect the crystaline structure of the silver to a greater extent
than either polysulfide alone or KRST. This is of no consequence for
pictorial negatives or prints.
     I have never seen any formal testing of KRST with added sulfide
or polysulfide.
     Kodak had a formula for making a combination toner from KRST and
KBT, I've posted it to this group a couple of times. Ryuji Suzuki
tells me he has tried it and found that it caused strong orange stains
on prints. Polytoner was discontinued some time ago but Kodak
maintains the secrecy of the formula.
      Gold toner provides very good image protection but does cause
some shift in image color for printing paper. The shift is toward blue
so may be desirable for some papers. The problem with Gold toner is
that it is expensive even at the relativly low concentration of Gold
used in protective toners.
       It appears that stabilizers, like Agfa Sistan, are effective
in preventing oxidation of the image silver. Sistan, in particular,
has not been fully tested. A test of a similar (but not identical)
Fuji products, called Ag-Guard, suggests that the effectiveness is not
as great as toning but is nonetheless significant. These products do
not affect density, image color, or crystaline structure.
    Highly diluted Polysulfide toners can cause serious staining.
Polysulfide has the peculiar property of toning faster as it becomes
exhausted or more diluted. For this reason the use of highly diluted
toner of this type is not recommended. In fact, the use of a 10%
solution of Sodium Sulfite is suggested as a sort of stop bath
following toning in Kodak Brown Toner or Agfa Viradon to prevent
staining from the toner remaining active in the wash bath. Washing
after toning should be quite vigorous even when this bath is used.
   I am skeptical of toning in a simple solution of sodium sulfide
since it does not affect silver directly. In fact, sodium sulfide is
used as a test of unfixed halide. It tones the halide very effectively
causing a stain if fixing is not complete. It does not significantly
affect metallic silver.

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

Sorry, Dan, but Mike is right on this.  

Selenium affects shadows before highlights.

First, I want to clarify a couple items from my previous post.  In my
previous post in this thread I had referred to research done at the
Image Permanence Institute at the Rochester Institute of Technology.  
The work was done by Dr. Douglas Nishimura, a research scientist at the
IPI.  In fact, I had occasion to inquire of him in and for a while he
posted to this news group some superb summaries of his research into
image permanence.  This was back in year 2000.   I had also mentioned
research done by participants in this group.  One such was undertaken by
Lloyd Erlick who summarized his results in a post started September 14,
2000, and entitled: "T-8 Brown Toner and Selenium Toner in
Combination".  Dr. Nishimura, Richard Knoppow and I were contributors to
that discussion.  I also at some point posted a chart of tonal changes
resulting from selenium toning  in various papers after development in
several different developers.

As to the affect of KRST on shadows and highlights, it definitely
affects shadows first.  I have myself done extensive testing (noted
above) to determine which papers exhibit what tonal change with
selenium, and in the course of those tests, I observed, consistently,
that tonal changes occur first in shadows, and only many minutes later
in the highlights.   I also have regularly engaged in split toning
(selenium/brown toner), toning first in selenium and second in brown
toner.  The result is that black tones remain black and highlights go
brown, while the affect on mid tones depends on the amount of time in
selenium.

This is not just my observation, however.   I refer you to Dr. Tim
Rudman's most recent book "The Master Photographer's Toning Book: The
Definitive Guide" (Argentum, 2003), where on page 42 he states:

   "Prints that have been fully selenium toned robustly resist attacks
by most image destroying chemicals.  However, not all the commonly
recommended archival toning regimes are valid.  This is a reflection on
the advice given rather than on the toner, because selenium toner
initially affects the shadow areas before the mid tones and highlights
and short toning times in highly diluted toner do not allow toning to
proceed far enough for all the image-silver to be converted.  The
highlights and possibly the mid tones may therefore be unprotected. "

Dr. Rudman also sites the IPI research.  See page 158 of his book.  On
page 159, he further explains that the shadow values have the finest
grains and that is why selenium tones them first.

The problem is that the color shift accompanying full selenium toning is
often unacceptable.  This is why many people try to selenium tone to a
point before the tonal shift occurs.  And this is why confusion arose
because KRST used to have a modicum of sulfurated potash in it.  The
potash provided protection in the highlights that the selenium was not
providing.  But with the "purification" of KRST, this subtle protective
affect was lost.  Thus, we have to deal now with the problem of how to
achieve protection without an annoying tonal shift.  Mike is on the
right track.  On further reflection, it may be better to use Kodak
Polytoner rather than Kodak Brown Toner, to get some potassium
trisulfide into the mix.

Francis A. Miniter

                               Dan

 The difference has to do with the size of the grains.
Finer grains have a larger surface to volume ratio than
larger grains so there is more surface to work on. This
seems to be at least part of the explanation. For some
reason polysulfide toners, where the polysulfides are of
higher orders, do not have this effect. Highly concentrated
stocks have lots of high order polysulfides.
 Sulfiding toners of other kinds can produce split toning.
For instance the old Hypo-Alum toner split tones. Indirect
toner split tones but that is due to the effect of the
bleach, not the toner. Both KBT and T-8 are concentrated
enough to tone evenly when used for partial toning. Agfa
Viradon is currently a simple polysulfide toner like KBT and
has the same properties. I am not sure the simple addtion of
sodium or potassium sulfide to KRST would cure its problems,
maybe so, but I am not a good enough chemist to know. I am
sure Dr. Nishimura, and his associates at IPI, must have
thought of this.
 I will also point out, that from personal communication
with Dr. Nishimura, that simple sulfiding is NOT as
effective as gold toning with Kodak GP-2. GP-2 remains the
standard of protection for microfilm. Diluted KRST was not
better, just a lot cheaper. (I've resisted calling GP-2 the
gold standard of protection, but I DID think of it).

...

...

apr2604 from Lloyd Erlick,

I think this could literally be done, and I'd
guess it is being done by many darkroom workers.

If you want a weight of potassium polysulfide
(liver of sulfur) to use, I'd say pinch your thumb
and index finger in a container of table salt and
weigh that. Weigh out that amount of sulfide for
each liter of selenium toner working solution. In
fact, this may be a bit too much.

The problem I had was the smell of the sulfide. It
gave off hydrogen sulfide (rotten egg gas). I
searched for an amount of sulfide I could put into
my selenium toner and not smell it, and also not
get a 'brown toner' toning result. I found a very
small amount of solid potassium polysulfide in
water could really stink the place up. But in view
of the fact that only a very small concentration
of sulfide in the toner will (apparently) provide
archival protection qualities, I think the
literally-a-pinch amount should do the trick.
Frankly, I'd be inclined to use a pinch per
gallon.

regards,
--le