Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,219   Posts: 1,532,222   Online: 831
      
Page 6 of 8 FirstFirst 12345678 LastLast
Results 51 to 60 of 77

Thread: Chemistry 101

  1. #51

    Join Date
    Jul 2010
    Location
    Southern USA
    Shooter
    Multi Format
    Posts
    3,769
    Quote Originally Posted by RPippin View Post
    I now always wear nitrale gloves when woking with developers, but sometimes they get into the glove on one hand
    You might try using a barrier cream on your hands before putting on the gloves. There are two types, one for working with water and the other for oil based products. You want the former type. I got mine at the local pharmacy.

    I am allergic to phenylenediamine and some color developing agents. Once you become sensitized to one developing agent you often become cross-sensitized for other ones. This is why I always discourage people from using ppd based developers. IMO, this developing agent is not necessary for todays finer grained emulsions.

    A researcher in organic mercury compounds died a few years ago. She thought that her gloves would protect her and didn't immediately remove them after a sihgle drop of methyl mercury contacted one of them.
    Last edited by Gerald C Koch; 09-30-2011 at 02:36 PM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  2. #52
    Roger Cole's Avatar
    Join Date
    Jan 2011
    Location
    Suburbs of Atlanta, GA USA
    Shooter
    Multi Format
    Posts
    3,835
    How many people make their own emulsion? Clearly some do, and some of those have little knowledge and even less sense. How many people are working with methyl mercury, or even mercury salts for intensifiers nowadays?

    That, I guess, was my point. Things like not adding water to acid we should know, granted, and using gloves for some stuff. Mask for mixing some powders. Other than that my darkroom chemistry is limited to "open a can of XXX developer...add to Y amount of water while stirring until dissolved, then add water to make Z.." or, at most, well tested published formula using the usual ingredients. I might use more or less sulphite or Kbr or benzotriazole than called for to tweak the results a bit but that's about it. For people doing no more than this it's no more hazardous than working with the stuff under the kitchen sink, as someone said - maybe less so. That requires care but should be a level of care we are all used to.

    If you're messing with some of this other stuff without thoroughly researching what you're doing then, yeah, you're a Darwin award waiting to happen and these warnings are justified.

  3. #53
    RPippin's Avatar
    Join Date
    Apr 2008
    Location
    Charlottesville Virginia
    Shooter
    Multi Format
    Posts
    276
    Images
    75
    Who was this guy Darwin? And how do I get one of those awards?

  4. #54
    Athiril's Avatar
    Join Date
    Feb 2009
    Location
    Melbourne, Vic, Australia
    Shooter
    Medium Format
    Posts
    2,496
    Images
    28
    Quote Originally Posted by Photo Engineer View Post
    There are several emulsion formulas floating around on the internet that were compiled by amateurs who know no chemistry. These in particular refer to making an acidified emulsion which uses citric acid during the make, and then which calls for ethyl alcohol to reduce bubbles or to aid in coating the emulsion. Well, this combination of Silver Nitrate, Citric Acid and either Methyl or Ethyl Alcohol is a route to disaster. Under the right conditions, it can form an explosive mixture! That is why I do not use acid in unwashed emulsions and why I use i-Propyl Alcohol.

    Now, how many knew that one? Of course I am not aware of any explosions by this route, but then why take the chance. OTOH, maybe we have not heard from people who have had explosions from this reaction as they cannot report their experience to us!

    PE
    I knew about citrates and explosives... it's anhydrous form in the baking section is had for very cheap at the supermarket.

  5. #55
    Athiril's Avatar
    Join Date
    Feb 2009
    Location
    Melbourne, Vic, Australia
    Shooter
    Medium Format
    Posts
    2,496
    Images
    28
    Quote Originally Posted by Photo Engineer View Post
    I think that due to some recent posts and threads here on APUG, it became obvious that people are doing a lot of "experimenting" who have no knowledge of chemistry at all and Jerry has jumped in to help save them from possible grief.

    I myself, have tried to prevent accidents when people were advised to heat chemicals in cook pots on the stove and etc..... Or, even heating chemicals in the microwave. All of these are dangerous practices that should not be done, especially for the average unprepared person. After years in the lab and seeing many accidents happen even to trained professionals, I advise caution of you are going into the "unknown" and ask the experts for advice.

    PE
    I hope people don't copy some of the things I do!

    Bromine Gas Bleaching #2 by athiril, on Flickr

  6. #56
    Rudeofus's Avatar
    Join Date
    Aug 2009
    Shooter
    Medium Format
    Posts
    1,590
    Images
    10
    Quote Originally Posted by Athiril View Post
    I hope people don't copy some of the things I do!
    flickr supports your stance and threw a safe browsing warning when I wanted to see your pic
    Trying to be the best of whatever I am, even if what I am is no good.

  7. #57
    Roger Cole's Avatar
    Join Date
    Jan 2011
    Location
    Suburbs of Atlanta, GA USA
    Shooter
    Multi Format
    Posts
    3,835
    Quote Originally Posted by RPippin View Post
    Who was this guy Darwin? And how do I get one of those awards?
    http://www.darwinawards.com/

  8. #58
    Athiril's Avatar
    Join Date
    Feb 2009
    Location
    Melbourne, Vic, Australia
    Shooter
    Medium Format
    Posts
    2,496
    Images
    28
    Quote Originally Posted by Rudeofus View Post
    flickr supports your stance and threw a safe browsing warning when I wanted to see your pic

    Actually flickr reviewed my account as safe, then marked it as restricted the next day, I complained and referred them to the previous review, they took it back, but then did it again the next day. Now they've ignored all my inquiries so far.

  9. #59

    Join Date
    Jul 2010
    Location
    Southern USA
    Shooter
    Multi Format
    Posts
    3,769
    Quote Originally Posted by Roger Cole View Post
    How many people make their own emulsion? Clearly some do, and some of those have little knowledge and even less sense. How many people are working with methyl mercury, or even mercury salts for intensifiers nowadays?

    That, I guess, was my point. Things like not adding water to acid we should know, granted, and using gloves for some stuff. Mask for mixing some powders. Other than that my darkroom chemistry is limited to "open a can of XXX developer...add to Y amount of water while stirring until dissolved, then add water to make Z.." or, at most, well tested published formula using the usual ingredients. I might use more or less sulphite or Kbr or benzotriazole than called for to tweak the results a bit but that's about it. For people doing no more than this it's no more hazardous than working with the stuff under the kitchen sink, as someone said - maybe less so. That requires care but should be a level of care we are all used to.

    If you're messing with some of this other stuff without thoroughly researching what you're doing then, yeah, you're a Darwin award waiting to happen and these warnings are justified.
    I agree with your post particularly the last paragraph,

    The point about the rubber gloves was to warn people who think that they are protected against all dangerous chemicals when wearing them is a false assumption. What's safe, what's not? I don't know. It appears that certain organic liquids readily penetrate them.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  10. #60
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    The chemicals commonly used in darkroom work do not easily penetrate either latex or vinyl gloves. It can happen, but it is quite uncommon with the things we usually use.

    PE

Page 6 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