Chromium intersifier problem

[dario]

Hi folks - I'd appreciate some advice on this one, please.

I had a neg that was underdeveloped, so thought I would try intensifying it. I'd never tried it before.

I bought some Fotospeed Cl10 chromium intensifier. It came as a single bottle of yellow liquid, presumably potassium dichromate. The label carried full instructions, which I followed diligently.

I diluted the intensifier 1:4 and dropped in the neg. I was expecting it to turn a yellowy-buff colour and to see the image virtually disappear.

In fact, the neg turned vivid green, not just the image area but the unexposed film edges as well. The image weaked a bit, but not much. I was a bit non plussed, so waited a minute or so until it appearred that nothing further was happening, then proceeded to wash the neg, as per the instructions.

The neg slowly turned blue, then the blue colour faded, but even after half an hour of washing it was still quite visibly blue. The image was still there, but somewhat reduced.

Next I put the neg into some working-strength Dektol, as per the instructions. In the space of 1-2 seconds, the neg turned yellow, the image disappeared, then reappeared.

Then I washed the neg and examined the result. The neg was slightly more contrasty than before, but very slightly, half a paper grade or less, not enough to justify all the drama.

So, what was with the green colour? Should I have got more contrast increase than I did? Has anyone else had the same experience?

I'd be most interested to hear.

 

[Mike Wilde]

general chrome intensifier info

Yes, fresh chrome intensifier of the sort that I mix from scratch from time to time is a vivid yellow/orange. I keep mine around for quite some time, as it lasts well. As it exhausts it turns green, (and is also less toxic in this form, I seem to recall).

After the intensifier, there is a paired clearing bath in my mix from scratch formula that cuts the washing time considerably, after a few minute soak. I think the sequence is chrome, rince, clear, wash.

May it be possible that the commercail mix that you used was mixed incorrectly, and the clearing bath ingredient waent into the intensifier, or that there was a second chemical product, the clearing bath, that was not a part of your bundle?

The result for me in intensifying is that the chrome gives a white 'ghostly' image, with yellow stain, and the clearing bath reduces the intensity of the yellow some, and the wash is continued until the yellow stain is gone. Then the neg goes into a diluted print develper, dektol, etc.

The final neg is a bit contrastier after one pass, as you indicated - don't expect miracles in one pass through. It can be iterated until the desired result is obtained (but don't expect miracles). Let the neg dry , then pre-harden before sending the neg through the process again, to buuild more contrast.

The chrome intensifier process does change the colour of the film base in some cases as well. The plus x I have done this to looses it's film bases' bluish tint, and ends up as a plain light grey.

There are formulas for mercury intensification, which are reputed to give contrast faster than chrome, but I would recommend against them, unless you want to end up like the mad hatter ala alice in wonderland, and have the EPA jumping up and down, even if you are good and take the used/exhasuted solution to your proper hazardous waste depot.

 

[Gerald Koch]

Was the negative well washed? If not, any reducing agent like sodium sulfite from the fixer can cause the negative to turn green.

Chromium intensifier produces only a modest amount of intensification, probably less than a stop. The process can be repeated but each intensification results in increased grain.

The negative can be redeveloped in a staining developer which will supplement the silver image with a stain image which will increase density,

The silver image can be increased by immersing the negative in a stronger than usual selenium toner solution. There is at least one thread describing this.

 

[dario]

Thanks for your responses. I did think of inadequate washing, but I have no evidence that it wasn't washed properly. The neg is 15-20 years old and showing no signs of deteriorating.

I quickly get out of my depth when talking about chemistry. I understand that fixers often contain a bit of sodium sulphite. But the neg went yellow the instant I dropped it into the Dektol (that is, reducing agent), so I don't understand why a bit of residual sulphite in the neg would make it go green.

On the other hand, the neg went green all over, including the unexposed edges, so there must have been something in neg that caused it to go green.