Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,283   Posts: 1,534,991   Online: 1011
      
Page 2 of 4 FirstFirst 1234 LastLast
Results 11 to 20 of 38
  1. #11
    Ian Grant's Avatar
    Join Date
    Aug 2004
    Location
    West Midlands, UK, and Turkey
    Shooter
    Multi Format
    Posts
    16,242
    Images
    148
    A 0.1% solution means 1 gram of Sodium Thiosulphate dissolved in Water made up to 1 litre.

    Ian

  2. #12
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    This is 0.1 gram of Sodium Thiosulfate Pentahydrate in 99.9 grams of Distilled Water. So the actual amount of solution used is very very tiny to use 100 mg (or 0.1 grams) of Hypo / 160 grams of Silver Nitrate.

    If you used 16 grams of Silver Nitrate, then you would use 10 ml of this solution (10 grams actually). If you used 8 grams of Silver Nitrate, then you would use 5 ml of this solution.

    After your emulsion is made and washed, you add this solution and heat to 60 deg C for about 1 hour. the time will vary. Without this treatment, the emulsion will be slow and low in contrast but with this treatment it can gain up to 3 - 5 stops in speed and 1 - 3 grades in contrast. You have to be careful though as you can fog the emulsion. I run a test before and after the hypo treatment to show the difference in result. To do this, I remove 10% of a 100 gram emulsion (10 grams) and coat it before treatment. I reduce the hypo addition by 10% to compensate and then retest to show the change in speed and contrast.

    This process is called Sulfur Sensitization or Finishing. It can be made stronger by using Sulfur + Gold. but that is another story.

    PE

  3. #13
    Malco_123's Avatar
    Join Date
    Feb 2009
    Location
    Canada
    Shooter
    Pinhole
    Posts
    10
    Quote Originally Posted by Photo Engineer View Post
    This is 0.1 gram of Sodium Thiosulfate Pentahydrate in 99.9 grams of Distilled Water. So the actual amount of solution used is very very tiny to use 100 mg (or 0.1 grams) of Hypo / 160 grams of Silver Nitrate.

    If you used 16 grams of Silver Nitrate, then you would use 10 ml of this solution (10 grams actually). If you used 8 grams of Silver Nitrate, then you would use 5 ml of this solution.

    After your emulsion is made and washed, you add this solution and heat to 60 deg C for about 1 hour. the time will vary. Without this treatment, the emulsion will be slow and low in contrast but with this treatment it can gain up to 3 - 5 stops in speed and 1 - 3 grades in contrast. You have to be careful though as you can fog the emulsion. I run a test before and after the hypo treatment to show the difference in result. To do this, I remove 10% of a 100 gram emulsion (10 grams) and coat it before treatment. I reduce the hypo addition by 10% to compensate and then retest to show the change in speed and contrast.

    This process is called Sulfur Sensitization or Finishing. It can be made stronger by using Sulfur + Gold. but that is another story.

    PE
    How critical is this process to produceing good plates? This is my first attempt at making an emulsion so this is all new to me. The rough Idea I have in my head is that I want to try and reproduce some period photos. The quality is important but not critical, mostly I just need to be able to get my hands on some of the materials. the overall ISO is important as I'm going to be using a pinhole camera and my fstop is going to be huge. All my shots will be outside in the sun so it shouldn't be that bad, plus it will be easier for me to do 30 second to 5 minute exposures than 1/2 second to 5 second exposures.

    What I'm trying to say is that I'm new to this and don't have a lot of disposable income, so I'm looking for a formula and process that is forgiving so I don't blow my entire budget by making a small mistake.

    but as I have learned analog photography is not very forgiving, so this request may be outragously naïve.

  4. #14
    dwross's Avatar
    Join Date
    Feb 2004
    Location
    Oregon Coast
    Shooter
    Multi Format
    Posts
    804
    Hi Malco,

    I think you'll be very satisfied with the results you get from Kevin's recipe. The best thing you can do at this stage of your learning curve is just plain make an emulsion. There's no substitute for a little hands-on experience. If you're interested in 'period' photography you don't even have to worry about spectrum sensitizing (just pick a period far enough back)

    I'm guessing that by huge fstop you mean a big number, so a small aperture. Pour a number of plates and use them sequentially to test your exposure. If you are consistent with your emulsion making process and testing, you should be able to get very close on the exposure time from your second and subsequent batches. By batch three, you'll be an old hand.

    You can order all the materials from the Photographers' Formulary in Montana. They have small quantities of everything you'll need, except for glass.
    http://www.photoformulary.com/DesktopDefault.aspx

    d

  5. #15
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    If you do use glass, you will need glass plate holders or something like it for your camera. Otherwise you can use the Melenex support sold by the Formulary and use it just as you would use sheet film.

    PE

  6. #16
    dwross's Avatar
    Join Date
    Feb 2004
    Location
    Oregon Coast
    Shooter
    Multi Format
    Posts
    804
    Melenex is a great product, but it gives a bit different look than glass. Also, especially if you are planning on pouring rather than spreading the emulsion, film is tricky to hold for a good pour (unless each piece is backed by a matching, or slightly smaller, piece of glass - something of a redundancy). Fortunately, it is very easy to make plate holders from old, wooden film holders. It pretty intuitive, but here's a short tutorial:
    http://www.thelightfarm.com/Map/DryP...ateSection.htm

    d

  7. #17
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Just an FYI, but you can tape a 4x5 sheet of Melenex to a larger sheet of glass or plastic and then pour the emulsion down the tilted "plate" letting the excess run off into a catch basin for re-use.

    This is the film version of coating plates. A little messy and hard but if you practice with plain gelatin with food dye in it, that should help you learn the basics in the light and with little cost. Just remember that only one side of the Melenex is coatable and the Formulary notches it properly to conform to normal practice with the notch in the upper right corner with the good side facing you.

    You will need to maintain the gelatin percentage and temperature to get a good flow using this method.

    PE

  8. #18

    Join Date
    Aug 2005
    Location
    Earth
    Shooter
    Multi Format
    Posts
    1,560
    Quote Originally Posted by Malco_123 View Post
    And silver nitrate is around 159.86 g/mol, so you were right.
    ???

    On this side of the world it is more like 169.87

    Be free of all deception, Be safe from bodily harm
    Love without exception, Be a saint in any form
    (Patti Smith)

  9. #19
    Malco_123's Avatar
    Join Date
    Feb 2009
    Location
    Canada
    Shooter
    Pinhole
    Posts
    10
    Quote Originally Posted by Ray Rogers View Post
    On this side of the world it is more like 169.87

    Oh, sorry must have messed up when adding the atomic weights.

    Also I'm picking up some 4x5 holders from a friend, but I don't think I will bother with them for the glass plates. I'm just going to slide em into a old pinhole camera I made and secure them in there. Plus I think film will be too flimsy and messy for me to start with so im going to go glass.

    Oh and a quick question. Is there any metals that the emulsion is particularly reactive to? I was thinking of spreading the emulsions onto a metal plate, probably copper, aluminum, or zinc, and then making the positive onto that. But I don't know if it will work because the emulsion might automatically oxidize (reduce?) when it is applied to the metal. does anyone have any experince of using metal as opposed to glass or film?

  10. #20
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Do not use copper, Aluminum, Zinc or Iron. The only metals that emulsions tolerate well are Stainless Steel and Titanium. They will corrode most others and in doing so will fog or spoil in some way.

    And, I missed the molecular weight as I have a small crib sheet due to my old age. Ray can attest to how old we are both getting. I'm sure he looked it up.

    PE

Page 2 of 4 FirstFirst 1234 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin