tone question for the chemists - brown tone developer.

I know with toning I can get various shades of brown on paper. But why can't that be done with the developer and save a step?

Example: could you add selenium or thiourea to a developer formula to turn the exposed silver halides to brown-ish rather than soft or cold shades of grey?
Warm tone developers on warm tone paper are still grey.
could it be done as a second developer before fixing?
I see from the toner thread that using pyro in the redevelopment is an olive tone, could that be done in an initial developer?

Or could the paper manufacturers reinvent the coating process such that the silver is mixed with other metals to change the color?

Just pondering.

Well first, lets look at how toning "works"...

First, the color effect we see on toned B/W prints is a function of print grain size... If I remember correctly, that if developed grains are larger than 5 millionths of an inch, the grains do not reflect light and appear black, but as they get smaller than that, they start reflecting different color wavelengths of light... The color scale from the reflectance of the larger grains starts from blue (from below the 5 millionths/") and as it gets smaller goes to greens/yellows/reds at about 2 millionths/"... (Paint pigments also work like this) So the smaller the grains, the redder the color... But smaller than that, and the grains don't appear any more...

When prints fade over a long time, the grains are attacked by contaminates and start shrinking until they reach the size scale above, and that's why you see old prints turning to sepia tones (mixture of red + yellow grains with some other remains of other color sized grains, but smaller than that and the grains don't appear any more (as in excessive fading)... In fact, the standard bleach and redevelop sepia tone process accelerates the breakdown that mimics the "aging" process that happens over many years, (but in two trays!!!) By bleaching, the silver is reduced to a barely visible state, but the toner "regrows" it back to a visible reflectance...

Now direct toners are usually a metallic salt that is attracted to the developed silver grains, and the deposits are in the reflective size range and cover the grains, providing the color, so mild toning will usually just change color to a slight cast, but upon very close examination the silver grains are the same size, but the toner reflects a different cast...

So back to the question, then if the reflective color is a function of grain size, so why can't we just develop the print grains to a size that reflects a color??? Yes, there was an Agfa formula that would do that in the back of the old books, but I had tried it and had little luck with it... It was a very dilute print developer that required very long dev times to build up the developed grains in a slow and controlled way (kinda like stand processing with film, but with developing times over 20min for the print, and even printing a test strip was an ordeal)... The print Dmax always was low, and even after the long development, the color would go back to cold tones and not reflect colors...

I think the issue is that modern, faster papers have larger grains that react much more quickly to development, and exceed that size range, so no grain reflection (even makes most papers hard to tone; Cold tone, large grained papers not at all, warm toned/smaller grained papers usually little if at all)... Old papers were very slow, with very small grain sizes, and even then, some would not respond... If you want to try, find the slowest warm tone paper you can find, like the Ilford... Most MG papers are too fast, and one emulsion layer might respond, but not the other emulsion might not...

So in a nutshell, that's the problem... So if you wanted to bleach and redevelop tone, it would be much faster to print dark, rich originals (that there is a heavy deposit of silver that will tone properly, and tone later... You don't have to stare at a blank test strip for an hour in the dark hoping an image appears!!!

Steve K

You might try this old Ansco developer formula - Ansco 110 Direct Brown-Black - though I don't know how well it will work with modern papers. Be sure your paper doesn't have developer incorporated.
http://johnesimmons.com/?p=1481

Thanks j.e.simmons - There is a similar formulation at PF paper developer 106 but it reduces hydroquinone and adds glycin. I don't know why I never noticed it before. I'm using the ilford MGFB papers and trying Bergger warmtone soon so I will have to determine if they contain developers within the paper.


"Formulary's 106 Warm Tone Paper Developer is equivalent to Edwal 106 and Ansco 115. It is a glycin and hydroquinone-based developer. Developer 106 is a specialty developer and is popular for the reproduction of old photos. Formulary developer 106 produces warm blacks to engraving brown on chlorobromide papers. The final color of the print depends upon the dilution of the stock solution. The prints have normal tonal separation and normal to low contrast. The chemicals in Formulary 106 are used to make a stock solution which is diluted 1:7 or up to 1:15 depending on the warmth of the tone desired. The stock solution is stable for 3 to 4 months."

I'll offer my thoughts at the risk of them being not wntirely informed and based on limited personal experience.

The problem with sulfur/sepia/thiourea toning is that both exposed and unexposed silver halides will develop. Hence, using it as part of a first developer will basically develop the entire sheet regardless of the exposed image.

With selenium toner, I believe the selenium attaches to metal sheetilver particles and not to halides. Hence, selenium added to a developer will tone the image as it's developed. The problem here lies in the concentration of the selenium. In a typical toning application, selenium toner will be diluted 1+10 to 1+20 and toning completes in 5 to 10 minutes. Typically when you develop a print, the development will be done in 1-3 minutes. The means you'd have to add quite a bit of selenium concentrate to the developer in order to get both processes to complete in tandem. I'm not sure what effect the selenium toner will have on the developer. The ammonia will alter the pH and this may affect the speed of development, but other interactions may occur, and I'd say (although I haven't thought this through in detail) that there's a chance that the selenium will drop out of solution when it's combined with a developer, rendering the toner ineffective.

A pyro developer will work just fine with a sufficiently high concentration and/or long enough development time.

All considered, a separate toner and developer step allows for more flexibility and efficiency, in my view.

From a practical rather than chemistry standpoint, controlling contrast and grain size during development, and any significant toning afterwards, allows quite a bit of fine-tuning that might otherwise be difficult. For example, today I made prints from the same paper and developer combination; but some were single-toned, some double-toned, and some triple-toned (gold, selenium, and sulfide brown). The effect of each of these can be fine-tuned by this sequential method.

I ordered the PF 106 warmtone paper developer and will give it a try with Ilford MGFB Classic, Ilford MGFB Warmtone, and Bergger VC CB Warmtone to see if it will print in a warm brown tone as described. My garage darkroom is a bit hot to work in right now so may have to wait for a cooler day. I scoured the internet but can not find anyone who has used this formula, it is slightly different than the Ansco 110 formula.

The papers that should work are very slow old contact printing papers, like Azo, as they are very small, fine grained/silver rich, but maybe papers that have an olive cast when processed normally, as the greenish color is from a # of grains that are in that color reflectance "sweet spot"...

But even if you get into the color range, the Dmax is low, so shadow regions will be weak, as there are few grains large enough to go black there...

Steve K

I'll be interested to hear about your results- perhaps you can post some pictures here when you're done. (Most of my successful warm-tone images involved Nelson's gold toner. Beautiful results but spendy and works at 100F)

Many of those old toner formulas waste gold like crazy. In many cases you can substitute time for concentration.