KODACHROME

[Photo Engineer]

Originally Posted by Helen B

Being silver (Carey Lea silver) it is removed by bleach.

Best,
Helen

Along with all other silver.......

So, if you are using a B&W process for Kodachrome, you cannot do this. In color, it is just fine.

PE

[AgX]

Helen,

Thank you for unveiling the term `CLS´. Especially as there are a few members from a non-English world.
The nature of this layer was known to me, but over here, and most probably elsewhere, it is referred to as a colloid silver filter layer. And I could not trace that abbreviation in my books even including the Neblette, Mees&Jones and many others written in English. (I finally found Carey Lea in the M&J bibliography…)
Interesting might be that Orwo once made such a layer obsolete because they experienced complex reactions with the adjacent layers causing a reddish fogging (`contact fogging´ in translation).

[CRhymer]

Originally Posted by Photo Engineer

Along with all other silver.......

So, if you are using a B&W process for Kodachrome, you cannot do this. In color, it is just fine.

PE

It is true that dichromate or permanganate will bleach away the CLS as well as the image. I have tried to selectively bleach the CLS and leave most of the image with some modest success, but as PE has said in another thread some time ago “…silver is silver”. However, I have been reading Grant Heist’s book Modern Photographic Processing and on page 260 of Volume I he says, “An acid solution of ammonium thiosulfate, especially a rapid fixer with a hardener, is an excellent slow-acting silver remover when 15 to 30 g of citric acid are added to a liter of the working solution of the fixing bath.”

He suggests this as a method to remove dichroic fog, on the basis that the fine grains of dichroic fog will be removed before the much larger grained image silver is removed.

I don’t know the actual size of CLS grains, but I suspect they are very small to be a blue filter.

I only saw this a few days ago and have not had a chance to try it.

Any thoughts?

Cheers,
Clarence