Ilford IIN-3 Chromium Intensifier

[Ian Grant]

For controlled intensification of negatives. This intensifier is not liable to produce stains.

BICHROMATE STOCK SOLUTION
Potassium bichromate 100 g.
Water to make 1000 c.c.
This solution keeps indefinitely.

BLEACHING SOLUTION A
Bichromate stock solution (as above) 100 c.c.
Hydrochloric acid (conc) 2·5 c.c.
Water to make l000 c.c.

BLEAcH1NG SOLUTION B
Bichromate stock solution (as above) 100 c.c.
Hydrochloric acid (conc) 12·5 c.c.
Water to make 1000 c.c.

Bleaching Solution A gives more intensification than Solution B.
Whichever solution is selected should be freshly mixed. Immerse the washed negative in the bleaching solution selected until it is completely bleached, then wash until the yellow stain is removed and re-develop, by white light, or after exposure to light, in an M.Q. or P.Q. developer. Wash the negative thoroughly before drying.

Ilford's IT-8 toner is similar using a Bichromate bleach then a Pyrocatechin re-developer. I'd suggest using Pyrocat HD as the re-developer as you get staining from the chromium and the Pyrocatechin re-enforcing the silver image.

[David Grenet]

Interesting. I saw you refer to this in the thread on thin negs - thanks for posting the formula!

[haryanto]

Can I replaced potassium bichromate with potassium dichromate Ian? it's hard to find potassium bichromate in my country, thanks

[Ian Grant]

Bi and Di just mean 2, Bichromate is just an alternative name for Dichromate, so no substitution is required as they are the same

Ian

[haryanto]

thanks Ian, it's clear now

[An Le-qun]

Variation on haryanto's question, with preliminaries: I am running low on Potassium Dichromate, but I have loads of Ammonium Dichromate. Can I substitute one for the other?

Also, are there any suitable substitutes for the H2SO4?

[Ian Grant]

You can't add Ammonium compounds to HCl without having problems.

There's no H2SO4 used in this intensifier.

Ian

[eclarke]

Ian, does the bleaching time vary much with different emulsions? I've tried persulfate bleaching on Tmax100, for instance, and it seems to have almost zero effect and on FP4 it's really quick..Thanks..Evan Clarke

[Ian Grant]

Yes there can be variations, it's sometimes quite noticeable, there's just too many variables try all combinations and Persulphates not as strong. The reason for the Dichromate bleach is critical because it stains as well as bleaches.

Ian

[eclarke]

Thanks Ian, It's sort of funny, I got on to this persulfate thing and decided I would give it a whirl. The first neg was Tmax 100 and I used a little white tray on a light table so I could watch it. I watched and watched and watched, almost zero effect. I made another batch and tried an FP4 neg, ready to watch it too and it literally disappeared before I could snatch it from the tray!!! I had to think about that for a while before I went back to the well...EC