Making collodion panchromatic?

[D_Quinn]

Hello, I make ambrotypes.
I know collodion is orthochromatic but is there any way to make collodion panchromatic or make it sensitive a little bit wider spectrum than what the ordinary collodion can see?
It may be impossible but I am curious to know if anyone knows about it.
Thanks,

 

[koraks]

When I did collodion, I did some reading (but no experimentation) in this direction.

The obvious route of expanding the sensitivity is to alter the mix of salts used in the collodion mix itself. This has a minor impact on spectral sensitivity, extending it into visual blue and perhaps a tiny bit of green. There used to be a neat set of examples on the site of Lund (?) but I can't find it presently. You may search a bit for yourself. But there's still this valuable paper that gives some clues: https://www.imaging.org/common/uploaded files/pdfs/Papers/1997/IST-0-4/159.pdf
Based on that paper, I adjusted my 'Poe Boy' collodion to use a 17/83 mix of bromide/iodide. To be frank, the difference with the normal Poe Boy formula was negligible in the real world...

I suppose dye sensitization is possible; you could try adding an ortho-sensitization dye to your collodion mix and see what happens. I'm a bit skeptical of the value of this, since the photon efficiency of a silver halide system apparently is reduced when dye sensitization is used. The net result is that you may extend the spectral sensitivity of the emulsion alright, but you'd need to compensate for this by throwing even more light onto the scene to reach the desired exposure. Since wet plate is very slow to begin with, I never actually pursued this direction.

 

[D_Quinn]

Hi koraks, thanks as always for the information.
I had a feeling that I would need to pay a price in order to gain sensitivity to a wider spectrum. haha
Do you have any information on adding ortho-sensitization dye, such as what kind of dye and how much dye I should add? I have never heard of this method so it would be helpful for me to understand it before I give it a try.

 

[retina_restoration]

I feel I should point out that if you do succeed at making collodion panchromatic, this will mean you can no longer work with a safelight. Just saying...

 

[Roger Cole]

No, but reaching orthochromatic sensitivity would go a long way toward normalizing the tones from your plates and still allow a red safelight.

 

[halfaman]

Do you have any information on adding ortho-sensitization dye, such as what kind of dye and how much dye I should add? I have never heard of this method so it would be helpful for me to understand it before I give it a try.

A typical dye for green sensitivity and what PE recommended for amateur work is erythrosine, not cheap at all these days... In some literature you can find also yellow eosine and rose bengal as possible dyes. In wet plate dyes shoud be added to the salted collodion, before silver nitrate sensitization. Quantites are not clear

 

[halfaman]

You can find here a useful link.

Wet Plate Collodion - ortho/panchromatic emulsion possible?

I am aware that the traditional wetplate formula with silver nitrate and bromide/iodine salt is only sensitive to Blue and UV light. What's stopping us from adding dyes (similar to gelatin emulsion formulae) to make the solution more sensitive to green (and potentially red)?

www.photrio.com

 

[D_Quinn]

Thanks, everyone for all the information and advice! The link looks helpful. I'll take a closer reading