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  1. #21

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    Several years ago I tried to make a 4x5 screen with a chemical for etching glass. I tried various methods of coating the glass including floating but could never match the eveness and brightness I could get with hand grinding.
    "Fundamentally I think we need to rediscover a non-ironic world"
    Robert Adams

  2. #22

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    The only thing that 'surprised' me was that after 20-odd minutes of grinding, there was still a small area of glass that was untouched. At first I thought it was me not grinding properly, then I realised that the glass couldn't have been perfectly flat to start with!
    Creative Image Maker e-magazine is back! Find out more at http://creativeimagemaker.blogspot.com

    Thank you.

  3. #23
    Christopher Walrath's Avatar
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    In any event, very well done, David. I might have to do one for my 4x5. One day just to tinker.
    Thank you.
    CWalrath
    APUG BLIND PRINT EXCHANGE
    DE Darkroom

    "Wubba, wubba, wubba. Bing, bang, bong. Yuck, yuck, yuck and a fiddle-dee-dee." - The Yeti

  4. #24
    RalphLambrecht's Avatar
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    Quote Originally Posted by canuhead View Post
    To get them to show up as large photos and not thumbs, they have to be hosted somewhere else. Upload them to your site, maybe make a subfolder (darkroomagic.com/apugpics/) for example, then link to that using the little postcard looking icon (mountains and sun) beside the quote icon above the text box.
    Thanks for the info. There does not seem to be an easier way. I'll just stick to adding them as attachments.

    Let's go back to the ground-glass discussion. Sorry for hijacking the thread.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  5. #25
    BetterSense's Avatar
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    what did you use for the grinding surface? Where does one get 600 grit SiC paste?
    f/22 and be there.

  6. #26

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    This is a reprint from an article in Photo Techniques magazine about grinding your own glass.

    http://www.dokasphotos.com/techniques/ground_glass/

    The author discusses using aluminum oxide as an abrassive. I used two different abrasive levels of automotive valve grinding compound which uses aluminum oxide. Just as in the article it took a lot longer than 20 minutes for mine IIRC.
    Last edited by Jim Chinn; 11-28-2009 at 08:25 PM. Click to view previous post history.
    "Fundamentally I think we need to rediscover a non-ironic world"
    Robert Adams

  7. #27
    nick mulder's Avatar
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    I've used an acid etch technique - I think it was hydrofluoric suspended in a manageable paste ...

    Bright enough
    Cleared the bowel problem, working on the consonants...

  8. #28
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    Quote Originally Posted by BetterSense View Post
    what did you use for the grinding surface? Where does one get 600 grit SiC paste?
    An auto parts or a hardware store will have a grinding compound....
    "Only dead fish follow the stream"

    [APUG Portfolio] [APUG Blog] [Website]

  9. #29

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    Quote Originally Posted by vickersdc View Post
    The only thing that 'surprised' me was that after 20-odd minutes of grinding, there was still a small area of glass that was untouched. At first I thought it was me not grinding properly, then I realised that the glass couldn't have been perfectly flat to start with!
    Here is a trick to grind a perfectly flat surface. You need three pieces of glass. You grind one against the other, swapping the pairs periodically so that every piece gets equal grinding time, and every piece gets ground against every other piece. (I think you are also supposed to periodically rotate the pieces by 90 degrees, but I am not 100% sure about this.) You do this until everything is evenly ground. The only mathematical surface that can survive this treatment is a plane, on all three pieces.

    I have never actually done it, but I read about it in a telescope making book.

    One more thing: glass is somewhat flexible, so if you did not give equal pressure across the surface then I think you might grind some areas more than other, and some areas might even remain un-ground for some time.

  10. #30
    clayne's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    Thanks for the info. There does not seem to be an easier way. I'll just stick to adding them as attachments.

    Let's go back to the ground-glass discussion. Sorry for hijacking the thread.
    Ralph, it's real easy. Just upload a photo as an attachment. On the manage attachments window just right click on the link to the attachment you uploaded and choose "copy link destination/target/etc." or open it in a new window and save the location in your cut/paste buffer.

    Then in the post you're still on, write [ IMG ] and then paste the link you copied and then write [ /IMG ] (remove the spaces between the brackets and IMG).
    Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.

    http://www.flickr.com/kediwah

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