U of S | Mailing List Archive | alt-photo-process-l | Re: Selenium-toning Van Dyke Brown prints

Re: Selenium-toning Van Dyke Brown prints

> From: "Loris Medici" <mail@loris.medici.name>
> Sent: Tuesday, September 26, 2006 9:35 AM
> Subject: RE: Selenium-toning Van Dyke Brown prints

> I was told that it's not a proportional toner; it tones the shadows
> and the highlights at the same rate/time. But you can see its effect
> a little bit quicker in the highlights.

From: Richard Knoppow <dickburk@ix.netcom.com>
Subject: Re: Selenium-toning Van Dyke Brown prints
Date: Tue, 26 Sep 2006 17:59:46 -0700

>     This is then the opposite of what it does to
> silver-gelatin. Selenium tends to tone the finest grains
> first. since they are the least sensitive they tend to be in the
> denser areas of the image so the shadows of a print tone before the
> highlights.

I wouldn't jump that far in the argument.

Toners work from the surface of metallic silver inward. Therefore, the
reaction will be faster where the surface-to-volume ratio (SVR) is
greater. (The design of Tektol Standard took advantage of this and
related facts to maximize SVR of image grains to enhance toner
reactivity.)  Finer grain is one thing, but even if you use
monodisperse emulsion, heavily exposed area will have considerably
greater SVR. This is influenced by the exposure, as well as the
emulsion and the developer.

I haven't seen electron microscope images of VDB exposed with step
wedge. My best guess is that the morphology does not vary much with
exposure, certainly less than silver-gelatin case. So there is no
surprise that selenium tones more evenly with VDB.

Loris said that the change in highlights is visualized earlier than
shadow. This may be just that the change in the lower density area is
less blocked by other nearby particles. Also, difference limen of
human eyes in this sort of detection is much greater in darker areas.

>     Has anyone tried a polysulfide toner, like Kodak Brown Toner, on
> van Dyke?

It's been discussed here several times.