Can cyanotype chemicals affect the emulsion on the negative?

[jcn]

I got myself a cyanotype kit to do some experimenting with contact prints from negatives...
I was wondering if anyone knows whether the cyanotype chemicals, once dried on the paper, can affect and degrade the emulsion of the negative seeing as they are touching during the contact print?
And, if so, is there a way to avoid or minimise it? (e.g. transparent sheet between film and paper, rewashing film afterwards, etc?)

 

[Bronson Dugnutt]

The ferricyanide in the sensitizer could conceivably bleach the silver in the emulsion, but isn't really a problem as long as the paper is *completely* dry. Paper you thought was 'dry enough' can quickly form condensation on the glass of your printing frame alerting you to the presence of water. A mylar spacer or contacting the base side of the film instead of the emulsion might be a bit safer and the loss of sharpness may or may not matter to your use case.

 

[MattKing]

Make sure you don't use T-Max 100 negatives.
They incorporate a UV blocking agent, which leads to very frustrating attempts to make a cyanotype or van dyke or ...
I have the almost blank cyanotype to prove it

 

[pentaxuser]

Make sure you don't use T-Max 100 negatives.
They incorporate a UV blocking agent, which leads to very frustrating attempts to make a cyanotype or van dyke or ...
I have the almost blank cyanotype to prove it

That's interesting and useful, Matt, and something I had no inkling of until you mentioned it Matt. So TMax 100 is a film that is unsuitable not to say useless of you intend to do cyanotype printing.

Does Kodak mention this in any of its spec/ processing instruction sheets?

pentaxuser

 

[Vaughn]

Does Kodak mention this in any of its spec/ processing instruction sheets?

Not that I am aware of -- and only TMax100, not 400. This is true for any process requiring UV exposure.

As long as there is not excess moisture, one's negs should be fine when exposing.

 

[MattKing]

Does Kodak mention this in any of its spec/ processing instruction sheets?

Not there.
I'm not sure how the information was originally distributed, but it was directed to the part of the market that uses traditional processes like cyanotype, rather than the photographic world as a whole.
There are whole classes of photographic endeavours in this world that have their own interests and own resources that are outside what is found in the basic, wide distribution manufacturer's information.
It is also mostly relevant to the relatively tiny coterie of photographers who use Large Format, because even 6x9 cyanotypes are kind of tiny for most purposes. Remember that cyanotypes, Van dyke prints, Kallitypes, etc. are all contact printing processes.
Of course in today's world there are a lot more people using digital intermediate negatives for the alternative processes, due at least partially to the cost, so for them the issue doesn't come up.

 

[FotoD]

I'd never put my negs directly against a paper with sensitiser on it. The humidity is never 0% and there's no way to know what the transfered molecules will do to the negs in the future. And a thin sheet of PE foil between them has surprisingly little effect on resolution.

 

[Andrew O'Neill]

I've never had any issues with the negative directly on top of sensitised paper, be it cyanotype, gum, or kallitype. I do however, place a mylar spacer when making carbon prints. This is with a UV LED exposure unit. If I use my halogen unit, then they all get a mylar spacer. 1000W halogen is hot, hot, hot!

 

[jcn]

That's great, thanks for all your replies! I'll get some thin mylar sheets - just on the off chance the sensitiser affects the emulsion in some way. I'm not expecting the definition of a cyanotype print on hand-coated paper to be so good that a thin mylar sheet will make a huge difference to how sharp it ends up looking...