sensitivity of Daguerreotype

[Marko Trebusak]

Firstly I hope the this is a right forum to post this question.

I'm researching old processes a bit. It's probably because I'm a trained chemist and therefore a nut . But for a start my question is quite simple: do anybody knows the sensitivity of Daguerreotype in modern ISO values?

Cheers,
Marko

[Bruce Schultz]

I do wet plate, not dags, but I feel safe in saying it would be less than an ISO of 1 or even less. Light meters are essentially of no use, so it doesn't really do any good to know the ISO.

[russyoung]

Hello Marko-

I made a few small (1/6 plate) dags back in the mid-1980s in Austin, Texas, using TLR cameras. Hazy or overcast days yielded irregular results but on bright sunny days, my exposure was F/8 @ 4-8 seconds. Mind you, I used only iodine and no bromine. A few experiments with Becquerel development dropped the speed by perhaps a couple of stops (alas my memory is a tad fuzzy on those).

Also made a few on pure copper, no silver plating, as J. C. Burnett suggested in period. Lovely for skin tones.

Good luck,

Russ

[Gene McCluney]

Hello Marko-

I made a few small (1/6 plate) dags back in the mid-1980s in Austin, Texas,

Also made a few on pure copper, no silver plating, as J. C. Burnett suggested in period. Lovely for skin tones.

Good luck,

Russ

I would be very interested in knowing HOW you got an image to form on a copper sheet, as the Silver reacting with the iodide vapors in the sensitizing stage, is what creates the photosensitive layer. Without the silver plating on the copper sheet I don't see how you would have a photosensitive plate?

[Jason Greenberg Motamedi]

A traditional plate is roughly .05 ISO, while a becquerel plate is about .005 ISO. However, since they are sensitive only to blue and UV light using a regular meter does not always provide accurate measurements.

[Jason Greenberg Motamedi]

I would be very interested in knowing HOW you got an image to form on a copper sheet, as the Silver reacting with the iodide vapors in the sensitizing stage, is what creates the photosensitive layer. Without the silver plating on the copper sheet I don't see how you would have a photosensitive plate?

Yes, me too. I can't see how CuI or CuBr would be light sensitive...

[Marko Trebusak]

Thank you folks for information. Russ, I'll add my voice to the chorus and ask you for details on how would you do image on pure copper.

Cheers,
Marko

[russyoung]

Well, folks, I don't recall the chemistry after 30 years either. Much of my time in those days was spent reading through The Photographic Journal (1859-1876) and its predecessor, The Journal of the Photographic Society of London (1853-1858). Charles John Burnett was a great genius in early (late 1850s-mid 1860s) photography and essentially unknown today. He was the first to make an image on platinum paper, for instance, and uranotypes. He was an early experimenter in stereoscopic photography and his research helped to take Poitevin's ideas and make them full tonal range, especially photographic images on porcelain. His mind seems to have wandered here and there, many vastly different questions grabbing his attention. Somewhere in all of that, he looked at whether dags could be made in a more practical manner and he simply noted that he did a few on copper.

I walked over the art department and filched some copper plates from printmaking. Having made dags already, I knew how to polish and buff them... my notes no longer exist (basement mold in Austin apartment) but I think they were simply iodized and exposed. They were slightly less sensitive than silver but not by more than a stop, methinketh. I showed a couple of them to Roger Baker and he also made some.

Although I cannot get the search engine at the Harry Ransom Center to work at the moment, the archive there holds at least one dag on copper by Roger Baker, an Austin experimenter in the 1980s (I know the search engine isn't working correctly because MY photos in the collection aren't showing up...).

Anyway, at least Burnett made a few historically and Baker and Young in the 1980s. Hope this had been of some help even though vaguer than I would have preferred.

Russ

[Marko Trebusak]

Hi Russ,

Thank you for your information again. Since you and Jason made Daguerreotypes I have another question for you: have you used original or Becquerel plates? I'm asking, because I would like to know, how you deal with mercury vapours? This thing is one of the main causes for me to be very, very sceptical of trying it out on my own.

Cheers,
Marko