UV transmission through Kodak safety Film

[stawastawa]

I went to make some cyanotypes and was surprised to not get an image after 1 hour in the sun.
Negative is on Kodak Safety Film, wondering if maybe it has UV blocking capabilities. A leaf cyanotype (also under glass, turned out fine in 8 min). Previous cyanotypes from negs on Delta 100 have taken under 30 min.

Process:
EHB 120 Ektachrome film (tungsten) (E3)
Developed in Rodinal various ways as BW
Classic Cyanotpe from photographer's formulary - single coat.
- in a contact print frame from my darkroom
- direct sun for 1 hour (in Colorado)

I got Dmax border (deep blue even after washing) and a faint image before processing, but washed away in water development.

Maybe someone who does Carbon, or albumen, or platinum or other UV process can chime in on if color films or safety films somehow inhibit UV transmission.

(also if someone would like to share target negative highlight density information that would be helpful information)

 

[MattKing]

I know that T-Max 100 blocks UV, while T-Max 400 does not.

So it probably depends on the film.

 

[Photo Engineer]

All color films have a UV absorber.

PE

 

[stawastawa]

All color films have a UV absorber.

PE

Does the UV absorber wash off during processing? is it part of the Anti-halation layer?
is there a pre soak that might remove it?

thanks for the info!

 

[Photo Engineer]

The UV absorber is in a special overcoat and it does not wash off.

PE

 

[stawastawa]

OK then, that might be the problem.
Do you have any information resources on which films have this?
Seriously all color films? is there a way to test other than to try a film?

 

[Photo Engineer]

All! Color! Films!

You see, all emulsions are sensitive to UV radiation. So, without a UV filter all 3 color layers would be exposed by any UV and you would get no colors at all for all practical purposes.

PE

 

[stawastawa]

Makes sense, funny i had never heard of it before. I recall looking at spectral sensitivity charts for some films but haven't found any for older films.

A shame the UV layer cant be removed, though I imagine it might help prevent aging of color films if poorly stored.

Thank you much for the responses, if you can refer me to any other resources about it I would be grateful.

 

[Photo Engineer]

You might try the books by Robert Shanebrook which are advertised here on APUG. They contain the full structure of a C41 film. It is also disclosed in many articles and patents.

PE