removing cyanotype from neg

[reinier_de_vlaam]

I accidently spilled some cyanotype chemo on a neg and noticed it

some time later when it was dried up. Is there a way to remove it,

without damaging the neg?

 

thanks

Reinier

[gauthier]

Well, if the negative wasn't exposed to light much, the cyanotype chemistry should wash away in water (was h the negative in running water for 15-30 minutes, then use a wetting aagent and dry). An alternative solution, I was told (I didn't try my it myself, so you might want to experiment on a bad negative first) is to bleach the negative completely in ferricyanide (that should get rid of both the silver image and the cyanotype stain), rinse and then re-develop with your favourite product. The developer, I understand, restores the original image on the neg.

[reinier_de_vlaam]

I tried flushing but that didn't help much

 

That 2nd alternative sounds extremely dangerous and I must say unlikely. If you dispose of the silver containing the image, there is nothing left to develop. Interresting enough to try but it can't be good for the image I guess

[silent1]

The reason bleaching and redeveloping works (at least with some bleaches) is that bleaching reconverts the silver to halide. Not all bleaches do this; permanganate and dichromate, IIRC, usually used in a sulfuric acid solution, convert the silver to a soluble sulfate that diffuses out of the emulsion; that allows their use in process like B&W reversals, where presence of sensitive halide replacing the first developer image would lead to a fully fogged slide at the end. Other bleaches, OTOH, (I think including ferricyanide) permit redevelopment (like those used in some color toning kits, which follow the bleach with a fogging color developer and dye coupler mix to deposit dye); these should be safe enough to try if simple washing doesn't clear the cyano material. I'd recommed testing with a scrap of exposed and developed film leader or similar -- if you can bleach, and the material darkens again on redevelopment, the bleach will preserve the image in your damaged negative.

 

Another thing you could try before bleaching, though, is soaking in a strong sodium carbonate or borax solution. Cyanotype that hasn't been toned (for instance, with tannic acid or tea) breaks down in an alkaline environment, and should then wash away. There is some risk, of course, as the long wet time means a chance of scratching the softened emulsion -- but it's your negative, you'll have to decide what process is most comfortable. After the soak, you'll want to wash and treat with wetting agent, as usual with any wet process.