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Thread: A real formula

  1. #41
    ADOX Fotoimpex's Avatar
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    David,

    you can use ADOLUX just like any other liquid emulsion for your first experiments in glass plate coatings. Basically the products out donīt differ much. But they are not really intended for the use in cameras. The liquid emulsions on the market today are used to make positive prints of already existing negatives and are sensitized up to about 560nm.
    This means they are orthochromatic (blind for red light) in order to be used under a red safelight and will reproduce anything red as black in the positive.
    Also they are rather slow and need long exposure times.
    The other problem is to get the emulsion to stick to the glass evenly.
    In this matter ADOLUX will not differ much from other emulsions but you need to sub your glass plates first. Recipes for such a preparation coating should be available on the site you mentioned, else Photo Engineer can probably shake a formulary for a subbing layer right out his sleeve. I could look something up for you otherwise.

    Cheers from Berlin,

    Mirko

  2. #42
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    Mirko;

    Good comments.

    A subbing layer is not normally needed, but one goes like this.

    10% gelatin 100 grams
    4 ml 5% chrome alum stock solution (stock is 10% chrome alum)
    5 ml Everclear (95% ethyl alcohol)
    1 drop 10% thymol in iso-propyl alcohol.

    This should give a good subbing layer for you coated using normal plate methods.

    If it is too thick, just dilute with distilled water in steps until the desired viscosity is reached.

    PE

  3. #43

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    If one could get they're grubby little hands on Gold Chloride, (there is some of questionable origin on Ebay) and I understand, from a wiki article that sodium hypo and sodium thiosulphate are the same chemical, what concentrations of these would you use of these. Since the formula calls for about .77 Mol of silver, and I read in another post that sensitizers should be 1 - 10 mg per Mol of silver, do we use (assuming the high end of that scale) about 4 mg of AuCl and 4mg of Na-Hypo (pardon the chemical contraction) or 7.7 mg of each?

    Also, I have seen other recipes that call for potassium Dichromate as a sensitizing agent. (unblinking eye.com) To my knowledge this only hardens gelatin when exposed to UV, which I would think help contrast, not increase sensitivity, and since it takes so long for the UV to harden the gelatin w/ K2Cr2O7, I dont seehow it would be of much use.

    Lastly Does the hypo and AuCl sensitize down to red, or just into green?

    THanks.

  4. #44
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    Silver halide is sensitized by adding thiosulfate at 1 - 100 grams / mole of silver present. Unfortunately, this level is based on grain size (surface area actually) and therefore unless you have electron micrographs you have to determine it by trial and error.

    Gold is used a 1 part of gold salt / 3 parts of thiosulfate.

    Don't use Dichromate.

    PE

  5. #45

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    Thanks-

    Just realized that the thiosulphate and and AuCl is for not for spectral sensitization - sorry for the stupid question.

  6. #46

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    Quote Originally Posted by totalamateur View Post
    If one could get they're grubby little hands on Gold Chloride, (there is some of questionable origin on Ebay)
    Go back to eBay, and buy from CJ Chemical or Salt Lake Metals. I've bought gold chloride and silver nitrate from both and they deleiver good product.

    Or, try Photographers Formulary.

    It's not so hard...

  7. #47

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    Hi,
    Stay away from Pro-Blenders L.L.C.on Ebay. Their silver nitrate will be cloudy in distilled water. When ammonium hydroxide is added it will be clear, but pink.
    Bill

  8. #48

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    Pink - that's pretty. I think that means there's manganese (pink at first, but it should turn brown on standing) or cobalt (was it blue for a little and then turned pink?).

    The silver nitrate I bought from Salt Lake Metals was water clear with dissolved in water, and it turned a very, very pale blue when complexed with ammonium hydroxide. Probably a bit of copper... which PE will tell us is a no-no... ACS and AR grade are allowed 2 ppm copper in silver nitrate.

    I suspect there was a bit more in the SLM silver nitrate I had, but I' guessing it was not much, as it was only blue with hydroxide and I only noticed the color when I poured it into a container so that it was more than a couple inches deep.

  9. #49

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    30 grams gelatin?

    Hi PE,
    I tried to make this formula, the full batch,not scaled down.
    Upon chilling to 33 degrees F, the batch was very soft, realy too soft for noodling. I used Formulary gelatin,and formulary Br and I. The only suspect component was the silver nitrate, which I have mentioned above. But 30g of gelatin in 1.5 liters of water is only 2% gelatin. Then you call for an adjustment to 5-10% gelatin. Something is not right,is it me?
    Regards,
    Bill

  10. #50
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    You! Sorry Bill. I have mad this over and over and over and it works. You made it in class. Sorry.

    PE



 

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