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  1. #11

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    Ok guys, before I try new batch using correct temperature as suggested by Photo Engineer (thank you) I've decided to rule out the possibility of a thin layer; this time I coated the paper with three layers. The results are MUCH better than last time as the surface turned very dark grey - almost black. Not ideal, but much better, so success

    Prof_Pixel: I've been using this wallpaper for years and I've never had a problem. However, I must admit that when I experimented with other fiber based papers, some of them had shown very different results.

    m.
    Last edited by martina.87; 01-14-2014 at 01:19 AM. Click to view previous post history.

  2. #12
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    It helps to understand that the word "emulsion" is a tad over-extended in use. Cyanotype and salted paper (Van Dyke, the 'browns', Pt/Pd) solutions are called emulsions but they are actually very thin liquids that soak right into the paper. The only way to increase the native d-max is to apply multiple coats and the paper type makes a tremendous difference.

    Gelatin-based processes (silver gelatin and carbon) sit on top of the paper they are coated on. The thickness of the emulsion can be controlled by both the amount of gelatin used and by the temperature of the emulsion or glop when it is applied to the paper. If you want a thicker coat you don't have to apply multiple layers, you simply cool the emulsion down a bit, or start with a recipe with a higher gelatin content. In fact, each layer introduces coating artifacts -- usually considered flaws, although that is strictly an artistic judgment, not a strictly technical one. As a matter of personal taste, I don't care for sloppy coating, but ymmv. A good emulsion, coated at the right temperature needs only one layer. Paper choice is important. You want a good wet strength and a texture and color that appeals to you, but beyond that, silver gelatin is much more forgiving of paper choice than the thin-only emulsion processes.
    Last edited by dwross; 01-14-2014 at 08:49 AM. Click to view previous post history.
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  3. #13
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    Coatings made using 5 - 10% gelatin and a doctor blade such as mine or Denise's will deliver a rather precise layer if the emulsion is at about 40C. This is quite repeatable. It will use about 12 ml of emulsion per square foot.

    However, I have found that pure bromide emulsions tend to give low Dmax when they are not "finished" with Sulfur sensitization or the Iodide treatment I mentioned above. Pure Bromide is kinda weird that way. So, thinking it over and looking at some of my own results, I have to add this cautionary paragraph.

    PE

  4. #14
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    may I ask what you are developing this home made emulsion in? Also what dilution and temperature?

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  5. #15
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    Martina, one more question...

    Was there much residue in your filter or in the making beaker?

    The reason I ask is that this kind of emulsion tends to make aggregates that settle to the bottom or get trapped in the filter. If this takes place, the amount of silver left goes down.

    PE

  6. #16

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    Photo Engineer: I am not using the blade; I like the brush look, plus I've never had any problem with it. I used to coat 40" x 60" canvases with my 5" brush. It took some time, but it worked.
    Regarding the filtration: I made another badge and I must say that there was quite a lot of residue left in the filter; perhaps I put too many cotton pads in. Do you think that pressing the filter is a good idea?

    Cliveh: I use Ilford Multigrade @ 1:9, 20 degree. I guess this isn't the ideal developer, but I have a 5 liters of the concentrate which I don't want to lose, so at the moment I am stuck with it.

    m.

  7. #17

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    Martina,
    Cliveh asked a very relevant question. I use, as my testing developer, Homemade D19 (recipe in APUG articles. No longer made by KODAK). I use this developer as a rather sever test for fogging. I always get good blacks, and have had to lower my Ag levels simply because I was wasting silver by having more than I needed to get true black. Yet, if I use pyro on the same emulsion, I cannot get true blacks. That is not simply because of the staining characteristics of pyro. The prints are just vet weak.
    Bill

  8. #18
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    Martina;

    I have used a brush and it gives an interesting look, but when all of these methods are presented in a workshop, the students prefer the smooth quality of a sheet coated with a doctor blade. And, BTW, using a brush may be affecting the amount of emulsion laid down. As for residue, if there is any, this is sucking Silver out of the final material and leving you short of imaging Silver. This should not happen. The formula should be revised.

    PE

  9. #19
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    Martina;

    Something I forgot to mention earlier. You might want to change to a gold coffee filter instead of cotton. This way you can see any residue more easily and filtration is quick and clean.

    PE

  10. #20

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    Quote Originally Posted by Photo Engineer View Post
    Martina;

    Something I forgot to mention earlier. You might want to change to a gold coffee filter instead of cotton. This way you can see any residue more easily and filtration is quick and clean.

    PE
    That sounds interesting. I managed to try different surfaces and I also managed to keep the temperature as close as possible; the results remain the same as at the beginning. I think that it could be caused by wrong filtration.
    I wonder if paper coffee filter would do the same job as the gold one.

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