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  1. #41
    mdm
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    more wedges, 35 min and 60 min exposure and a sample of the sensitised tissue for a deep black.
    Attached Thumbnails Attached Thumbnails diazo2.jpg  

  2. #42
    CMB
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    It is quite clear to me why the plant blew up!

    Good luck, but my advice is to be careful, be very very careful!
    PE





    You are perhaps confusing the manufacturing of azide compounds (a dangerous process) with the use and storage of the finished compound.

    Hardnener #3 required no registration/regulation with the U.S.Dept of Transportation and was relatively inflammable and safe to use. I don't know if the plant blew up making this chemical or another.
    Last edited by CMB; 07-13-2011 at 11:34 PM. Click to view previous post history.

  3. #43
    mdm
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    This is what wikipedia sayes about azides. Mr Mowrey may be right.

    "Azide is the anion with the formula N3−. It is the conjugate base of hydrazoic acid. N3− is a linear anion that is isoelectronic with CO2 and N2O. Per valence bond theory, azide can be described by several resonance structures, an important one being N−=N+=N−. Azide is also a functional group in organic chemistry, RN3.[1]

    Sodium azide is found in automobile air bags; it decomposes on heating to give nitrogen gas, which is used to quickly expand the air bag. The antiviral drug zidovudine (AZT) contains an azido group. Some azides are valuable as bioorthogonal chemical reporters."

  4. #44
    CMB
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    Quote Originally Posted by CMB View Post

    Hardnener #3 required no registration/regulation with the U.S.Dept of Transportation and was relatively inflammable ...
    I meant to say it was neither listed as an explosive or flammable material nor was it considered dangerous by our manufacturing (coating) facility and required no special handling.

  5. #45
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    I suspect that the formalin addict or the zinc complex of these reduces their instability.

    Remember, a compound that is not explosive or flammable is not necessarily stable. These azides have a finite lifetime I would think. And, Sodium Azide is indeed explosive when heated.

    PE

  6. #46
    mdm
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    I am told it is a class 4.1 (flammable solid) so definately not possible to ship overseas, it has to be kept very cool, in a fridge. It may be possible for people in the USA but the safety aspect is yet to be fully explored, at least by me.

    http://en.wikipedia.org/wiki/HAZMAT_...ammable_Solids

    Probably best to stick with some sort of screen printing sensitiser.
    Last edited by mdm; 07-14-2011 at 06:49 PM. Click to view previous post history.

  7. #47
    mdm
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    The clearing bath quoted earlier in this thread works fairly well. Amazing to watch the wedge go purple in the 1st bath and then raidly clear in the last, leaving very little stain behind. The RC paper I used seems to hang onto a faint yellow even cleared twice. The relief is very fragile in there and is prone to rubbing off/dissolving away so times quoted are probably the maximum. I will post a cleared wedge when it is dry.

    David

    PS Stick to the times for each bath, 1 minute, no agitation required I dont think, dry before washing I think or the highlights will wash away. Any residual yellow stain goes with the wash water. Its possible I am using the wrong concentration Sodium Sulfite, I am using anhydrous.
    Last edited by mdm; 07-15-2011 at 12:36 AM. Click to view previous post history.

  8. #48

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    David, I'm wondering if a lower concentration of sensitizer in the glop might help limit staining, even though it would probably increase contrast and lower speed. Less dye hopefully would mean less staining. I'm also wondering if a pre-soak (prior to clearing) would help clear more of they dye stain.

    Also...did you check to make sure the table salt you were using was non-iodized (& that there were no other additives, like to prevent clumping)? I don't know if any of those things could have interfered with the clearing process.

    --Greg

  9. #49
    mdm
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    Sometime next week I will do a pour with less diazo sensitiser in it.

    Clearing, drying, washing leaves a yellow stain but maintains the integrity of the transfer. Clearing and then washing works about the same.

    2 clearing cycles and then immediately washing cleared the stain but I left my wedge soaking in the sink and when I came back 2 hrs later it had started to dissolve.

    There is a balance that will work. Stain may not be a problem with some supports.

    This is RC paper I am working with and only the coated side stains, not the back. Something in there is reacting with the diazo. Gelatine sized watercolour paper will probably be fine.

    I am too busy now to spend time on this, but it is a workable option and I hope someone will be able to repeat my results soon.

    Yes, non iodised salt was used.
    Last edited by mdm; 07-15-2011 at 07:36 PM. Click to view previous post history.

  10. #50

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    I am by far no expert, but does anyone think that Titanium Dioxide could help decrease exposure times? According to the wiki on TiO2 "Titanium dioxide, particularly in the anatase form, is a photocatalyst under ultraviolet (UV) light."



 

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