Colior sensitivity of Experimental Emulsion
Hello to All,
I wish to make an emulsion suitable for color separation work. I took a shot of a Kodak chart in mid-day clear sunshine. Bellows factor was 2.3;F11;one second exposure. Developed as usual.
Your blue speed is way above red. Green is in the middle kinda. In fact, the blue is greatly overexposed I think, compared to the other two.
Do you think that simply uping the dye adition would sufice? I mean, with a fresh batch, not just adding dye to the existing batch..
Yes, it probably would hellp, but remember that sensitizing dyes are also antifoggants and you can therefore lose blue speed and overall contrast.
Nice job with those polymers Bill.
These balances look really, really close, Bill. I'll have to borrow those night vision goggles of yours and give it a try with gelatin!
Your gray scale looks good (accounting for the variations in density with your coating) and on the second column from the left, at the bottom, the relative values of the magenta and blue look very close. If I had to identify one area that needed work, it might be the greens, but really excellent all-in-all. Congrats! Once you get a coating protocol that is manageable in dead darkness, you'll have it made .
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I have read the latest entries on the "Really Large Plates" thread here. I wonder how you controle wet thickness. As I understand it. You position the glass plate in the middle of 4 frame plates, then just cathetor on the emulsion,in the Center, and let it flow out. Are the frame plates higher than the emulsion plate?
All - Triton X-100 appears to eliminate the dewetting of the emulsion on clean glass. I drop for 250g emulsion. This sufactant appears to me to be very effective for PVA based emulsion.
With a gelatin emulsion, the thickness is controlled by the play between emulsion temp (i.e. viscosity) and the gap distance between the individual plates and dam bars around the perimeter of the plate line-up. I've always used dam bars that are the same thickness as the plates and been fine. The plates are at room temp and by the time the emulsion has spread over the plate and off the edges it has started setting up. I've been getting perfectly even coatings. But...I've been coating formats that are close to square. Michael (studiocarter) is coating elongated rectangles. He's made his dam bars just a tad thicker so that he can pour the emulsion at one end of a plate and then use a straightedge -- riding on the guide bars on each side of the plate -- to push the emulsion down the length of the plate.
Since you aren't working with gelatin, the system might need further tweaking for you. First, your emulsion doesn't 'set up'; it dries, right? What is the viscosity? Is it like cream (that's how I'd describe coating viscosity gelatin emulsions) or like Elmers glue? Either way, I can see that you'd like to have your guide bars thicker than the plates, but also instead of just lining up the plates, you'lll need the thicker glass between them, in effect surrounding each plate, so that your emulsion is dammed at an equal level on all sides. Hope that makes sense.
Just for reference, one layer of Scotch Tape is about 2.5 mils and of course 2 layers is 5 mils. It does wear fast, but it can give good results providing a gap for coating.
Really nice seeing you making progress with your experiments.
I know this is not 100% relevant to your work and this thread, but I would like to point out a link to a book I recently discovered. It is a book about coatings applied to photographs. Although this is not like your light sensitive emulsion, since we're talking coating layers applied as protective top layer to developed photos (from the daguerreotype to modern day plastic lamination), the (conservation) research in the book seems very interesting and may give some ideas or be fun to read in the context of your current work:
I referenced it in this thread:
Don't forget to have a look at the linked PDF "sneak preview" of one of the chapters as provided by the Albertina Museum. This PDF also contains the Contents section of the book, so you get a better idea of what the book is about.
"The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true.
" - William M. Ivins Jr.
"I don't know, maybe we should disinvent color, and we could just shoot Black & White.
" - David Burnett in 1978
"Analog is chemistry + physics, digital is physics + math, which ones did you like most?
That a good tip. It would depend on whether or not you needed a higher-than-the-plate dam (for stopping and set-up, or stopping and drying purposes) but if you just needed a higher surface for the straightedge to ride on, tape would be a dandy way to have just one set of guide bars around.
You can also tape the ends of the straightedge (or puddle pusher type glass rod), of course. Again, depends on the list of emulsion-specific and/or format-specific requirements for the edging glass.
Thanks for that link! I saw it when you first posted and I ordered the book. Very much looking forward to reading it.
Last edited by dwross; 07-07-2011 at 02:20 PM. Click to view previous post history.