Iron Blue GAF 241

Could someone possibly explain some chemistry to me. Since making Ilford MGIV Classic FB my standard paper, I have been experimenting with various home made sepia toners and really like the results I’m getting. The colours are more muted and controllable than MGWT. But, as Classic doesn’t change much in Gold toner, I’ve been looking for a way to imitate that cold look. So I made up a litre of GAF 241 Iron blue toner, then made a very diluted toning bath of 50mls of stock toner in 1 litre of water, and got the slate blue colour I was after. However, I took a some prints a little to far in the toner and decided to remove it with weak PQ print developer. This is the bit I don’t quite understand, the developer reduced the strength of the blue tone but the high lights and the midtones started to turn a pale sepia. I think it is to do with the ferricyanide in the blue toner mix bleaching the print slightly, and then being re developed by the PQ.

David - I will be very interested in how this thread goes as I have done a lot of sepia, gold with Iron Blue , and its so hit and miss for me I
have moved to pigment over palladium to get what I want.

good luck and post images as you play with this.

Bob

Thank you both. Michael, I'll try and source that additive in the UK.

Iron Blue toner is in no way comparable to blue tone developer, and also not to treatment in gold toner. Blue tone developer creates a granular structure in developed silver which absorbs more yellow/red light and/or reflects more blue light, and gold toner coats silver with the more inert gold and thereby apparently also creates this effect. Iron Blue toner, however, replaces silver grains with another compound that happens to be blue. It does this by bleaching the silver grains back into silver ions which then react with some part of this blue toner to firm a deep blue compound. That compound is less stable than metallic silver, and photographic developer will destroy this compound and recreate metallic silver, and after many, many years, light will eventually do this, too.

We also know three things:

1. If you bleach and fix a B&W print, there will be some brown residue, usually formed by Silver Sulfide.
2. Iron Blue toner will behave just the same, but cover the faint brown image with deep blue compound. It's there, but you won't see it.
3. Whenever you bleach and redevelop, and that's essentially what you do if you blue tone, then redevelop, you lose some silver in the mid tones and highlights.

This allows us to conclude, that the pale sepia was already there when you blue toned your image, and redevelopment together with the bleaching done by the blue toner only exposed the already present Silver Sulfide, and that's what gives you that pale sepia tone now.

Thank you Rudeofus.