Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,503   Posts: 1,543,430   Online: 847
      
Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 22
  1. #11
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,007
    Images
    65
    Jim;

    No, it would not. In fact, it is the worst thing to do. You end up adding heat and water to a mixture that needs both to harm skin! So, adding bicarbonate is the last thing you want to do before you wash it off.

    PE

  2. #12

    Join Date
    Jun 2004
    Location
    Portland, OR
    Shooter
    4x5 Format
    Posts
    3,268
    Quote Originally Posted by Photo Engineer View Post
    So, adding bicarbonate is the last thing you want to do before you wash it off.
    I knew someone that used the same reasoning as Jim and put some soda ash on the sulfuric. He got a very bad burn from it.

    Sulfuric is hygroscopic and will pull water from your skin or other organic compounds. It does take a little time for the reaction to get going - you'll know when you get it on you and hopefully it will give you some time to wash it off.

    Add a little sulfuric to a little sugar and see how it reacts strongly - the sugar is dehydrated and the reaction leaves only carbon behind. It's quite impressive - see this video here: http://www.youtube.com/watch?v=uaB70TgLfqs

  3. #13

    Join Date
    Nov 2004
    Shooter
    Multi Format
    Posts
    2,055
    Gentlemen, thank you. You learn something, or should learn something every day!

  4. #14
    Ole
    Ole is offline
    Ole's Avatar
    Join Date
    Sep 2002
    Location
    Bergen, Norway
    Shooter
    Large Format
    Posts
    9,281
    Blog Entries
    1
    Images
    31
    Not a good idea at all.

    Mixing a concentrated acid with bicarbonate shouldn't be done anywhere near skin - not only does it effervesce spreading acid around, but it's also exothermic enough that (heat) burns are a real risk in addition to the acid burns!

    -----

    this was a belated reply to Jim's question - for some reason it took a long while from i pressed "post" until it was actually posted.
    Last edited by Ole; 02-11-2008 at 10:33 AM. Click to view previous post history. Reason: Update
    -- Ole Tjugen, Luddite Elitist
    Norway

  5. #15

    Join Date
    Oct 2004
    Location
    Rome, Italy
    Shooter
    35mm
    Posts
    884
    Quote Originally Posted by Photo Engineer View Post
    Cupric Sulfate is a well known bleach for films. There are many patents on it in the literature. I have worked with it myself. The problems are threefold; the first is that the bleach will not work if there is not enough acid, and the second is that the copper salts can stain the film or paper and cannot be removed and the third is that these bleaches are very slow in most cases. There are also blix formulas.

    Concentrated sulfuric acid (Oleum) is pretty much unobtainable. You can get dilute sulfuric acid at auto stores (about 37%) and from the Formulary (about 48%). The 48% is the highest that can be shipped now in the US without a special license.

    A drop of oleum on the skin does not cause immediate burns due to lack of water. It needs water to react. So, immediately start a huge flow of cold water in the nearest tap and wash it off as quickly as possible with as much water as possible. Do not leave it on the skin for over 30". When you wash it off, you will feel an instant burning sensation and a lot of heat, as the reaction starts. If you wash with enough water, fast enough, no harm will be done in most cases. Once rinsed well, put some sodium bicarbonate on the affected area for about 1/2 minute and then re-rinse in cold water. If the skin is broken, call a doctor or go to emergency immediately. Do not get it in the eyes.

    PE

    I remember it didn't work at all (variation a). Someone suggested to put some NaCl in it. Dunno why.

  6. #16
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,007
    Images
    65
    Cant help you at all. I have used them, they worked, but they were very slow in the experiments I ran. The solutions that I used were pale blue-green.

    PE

  7. #17
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,007
    Images
    65
    I would like to add that anyone calling a mixture of cupric sulfate and sulfuric acid "non toxic" is fooling themselves. Also, make sure that if you do try to make up this bleach that you use the cupric sulfate and not cuprous sulfate. Cuprous sulfate will not work at all.

    PE

  8. #18

    Join Date
    Oct 2004
    Location
    Rome, Italy
    Shooter
    35mm
    Posts
    884
    Quote Originally Posted by Photo Engineer View Post
    I would like to add that anyone calling a mixture of cupric sulfate and sulfuric acid "non toxic" is fooling themselves. Also, make sure that if you do try to make up this bleach that you use the cupric sulfate and not cuprous sulfate. Cuprous sulfate will not work at all.

    PE

    I did use cupric sulfate as used in gardening.

  9. #19

    Join Date
    May 2006
    Shooter
    Medium Format
    Posts
    667
    Quote Originally Posted by Norman Christie View Post
    Could this bleach (variation b) be used in lith printing. Sulphuric acid is very difficult to get.
    I've just come to this a bit late, but yes and no. You can use a cupric sulphate bleach with spectacular results for print redevelopment in lith (if that's what you meant?) but you need a halide. Sodium chloride (pure, not table salt) is ideal.
    Conc sulphuric acid is typically 96 -98%. The Photog' Formualary sulphuric acid is 48%. Adding double the amount of this works fine. This is what we use on my workshops there.
    If you need the formula I can provide - but it is in most of my books.
    Tim

  10. #20
    nick mulder's Avatar
    Join Date
    May 2005
    Shooter
    8x10 Format
    Posts
    1,204
    Images
    14
    hmmm,

    maybe I'm lucky in NZ - got both %98 sulphuric acid (almost gloopy in consistency) and Pot Dichromate from the same supplier ... Pretty cheap too.

    I've spilled it once and that was on purpose to see its effects, cleaned up a small spot on the concrete garage floor - I use gloves, googles with and a mask when using the powders, also tend to do it when someone else is in the house in case I incapacitate myself somehow (unlikely though)
    Cleared the bowel problem, working on the consonants...

Page 2 of 3 FirstFirst 123 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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