Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 69,903   Posts: 1,521,216   Online: 1104
      
Page 2 of 8 FirstFirst 12345678 LastLast
Results 11 to 20 of 75
  1. #11

    Join Date
    Nov 2007
    Shooter
    4x5 Format
    Posts
    187
    Thanks Denise, that's just what I wanted to hear!

    It may be several days before I can post the results of more testing, but I certainly will.

    thanX again :-)

  2. #12
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,918
    Images
    65
    Quote Originally Posted by tim_bessell View Post
    Yes, I guess it is low in contrast, if you consider the dMax is only 1.63. But here is the kicker. I have printed a negative that was made for a Kallitype and it looks pretty good for a first, quick, and dirty attempt.

    As I mentioned above I would like to experiment with the developer to try and adjust contrast to suit the negative I wish to print.

    Do you think that's possible?

    The emulsion is Denise's 1A from the Light Farm without add KI.

    ... and thank you for your comments.
    Tim;

    The KI might boost contrast, or the contrast might be low due to the type of salt that you used. Sea salt often has other positive ions that can affect the grain type (good or bad).

    The amount of silver coated is also critical to contrast and dmax, and that might be another source of the low dmax and low contrast.

    But, as you say, it makes good pictures and that is what counts.

    This is a takeoff on an early pure chloride emulsion without the active gelatin so that is another factor in speed, contrast and dmax.

    If you wish to raise contrast, adjust the gap (undercut) in your coating blade. With that formula the gap can be from 5 mil to 10 mil and as you go up, contrast and dmax will go up due to the rising level of silver.

    If you cannot get everclear, you will find that i-propyl alcohol will work as long as it does not have any of the denaturing ingredients that cause it to become cloudy when added to water.

    PE

  3. #13

    Join Date
    Nov 2007
    Shooter
    4x5 Format
    Posts
    187
    thanX for the ideas PE.

    I did understand that potassium iodide would raise contrast and that is why I omitted it as a final addition. That and my interest in chloride emulsions.

    The speed is pretty fast, my exposures with a 40 watt bulb, 32 in. from the print frame are 16 sec. Could almost be an enlarging paper.

    Right now I am using an .008 gap on the blade; earlier attempts using .005 and .006 gave me very uneven coatings. Of course, you learn and modify your methods as you go to get results you want. So I am still in the very early stages of sorting out the basic techniques.

  4. #14
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,918
    Images
    65
    My exposure time is less than 1/2 that with about the same conditions.

    By tests, my paper is 5 stops slower than enlarging paper on-easel.

    As for the uneven coatings, did you use any Photo Flo? Lack of a surfactant can cause some sever problems in coating. Denise uses Photo Flo 600 and I use Photo Flo 200. They differ by a factor of 3 in concentration and one uses EG, while the other uses PG for lower toxicity (PF 200). I use PF 200 due to the lower toxicity and also the fact that I can use 3x the amount and this leads to better accuracy in repeat experiments. It is hard to measure a half drop.

    PE

  5. #15
    Vaughn's Avatar
    Join Date
    Dec 2006
    Location
    Humboldt Co.
    Shooter
    8x10 Format
    Posts
    4,623
    Images
    40
    PE -- I use Photo-flo 2100. Anything I should be looking out for with that one?

    Vaughn
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  6. #16
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,918
    Images
    65
    Quote Originally Posted by Vaughn View Post
    PE -- I use Photo-flo 2100. Anything I should be looking out for with that one?

    Vaughn
    It is merely a matter of EG vs PG and toxicity and also the ability to measure tiny quantities.

    PE

  7. #17
    Vaughn's Avatar
    Join Date
    Dec 2006
    Location
    Humboldt Co.
    Shooter
    8x10 Format
    Posts
    4,623
    Images
    40
    Quote Originally Posted by Photo Engineer View Post
    It is merely a matter of EG vs PG and toxicity and also the ability to measure tiny quantities.

    PE
    Thanks, PE -- I should have looked it up first.

    I mix 7 oz. with water to make a gallon of stock solution, then the students take one oz. of the stock to make a gallon of working solution. Very strange stuff.

    Contains OCTYLPHENOXYPOLYETHOXYETHANOL, which according to the MSDS, does not sound too bad (keep it out of the eyes and the concentrate off the skin.) Also, POLYETHYLENE GLYCOL -- I assume that is the PG you referred to.

    Vaughn
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  8. #18
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,918
    Images
    65
    PEG = Polyethylene Glycol but PG can equal Propylene Glycol and PPG is Poly Propylene Glyol. The Ethylene derivatives are more toxic than the Propylene derivatives. EG = Ethylene Glycol. Propylene derivatives are safe even as food additives but the Ethylene derivatives are deadly poisons and cause kidney failure.

    I am not sure how the polymers stack up vs the monomers of these glycols regarding overall toxicity.

    PE

  9. #19

    Join Date
    Nov 2007
    Shooter
    4x5 Format
    Posts
    187

    Coating blade rough drawing w/dimensions

    I used Google SketchUp to draw the coating blade I fashioned from 1/2" plexi and stainless steel. I am attaching a jpeg which is a little large so you can see the general dimensions. I am also attaching the SketchUp file ( fingers crossed.)

    The drawing only shows the plexi-glass body, it would be 2 complicated to draw screws and the 'blade' is just a cheap 6" stainless rule.

    Several notes:
    You will notice a small hole at the end of the slot that houses the blade. This is to prevent the plexi from cracking as the screws are tightened to hold the blade in position. I drilled these holes first and then sawed the slot to the hole on the bandsaw. I used 10-32 stainless steel button head socket screws. The holes for the screws are tapped just on the bottom, longer section so when the screw is tightened the plexi is squeezed to clamp the blade. Be sure the blade doesn't touch the screws or it may move as the screws are turned, defeating the purpose of the design.

    Kirk asked how far the blade is from the body. ~3/64" Of course, I do a lot of eyeball engineering; build to suit.

    SketchUp is free! Look for it on Google.

    I guess I can't upload the .skp file, so if anyone wants it just suggest a method to make it avialable.
    Attached Thumbnails Attached Thumbnails CoatingBlade.jpg  

  10. #20
    dwross's Avatar
    Join Date
    Feb 2004
    Location
    Oregon Coast
    Shooter
    Multi Format
    Posts
    798
    I tend to avoid drinking darkroom chemicals, or, breathing deeply as if we were talking about fresh apple pie (although I have to fight the temptation with fix -- yes, I'm one of those ).

    I actually don't use particularly small quantities of PF600, but it does bring up an important topic in emulsion making. There are many chemicals that are used in very, very small quantities, especially when you scale down for home darkroom-sized recipes. The solution to the problem is to make a solution, i.e. mix a quantity of the chemical that can be accurately weighed with your particular weighing apparatus with water, most easily 1 liter, and then add the number of mls of the %-solution that will give you the miniscule amount called for in the recipe. A Google search will give you all the details you could possibly need, or see Steve Anchell's The Darkroom Cookbook (Disclaimer: Steve is a friend. Still, he's written a great book that I wouldn't be without.)

    d

Page 2 of 8 FirstFirst 12345678 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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