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Thread: what grit for ground glass

  1. #1
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    what grit for ground glass

    I have 400, 600, 800 grit SiC grinding powder. What is best?
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    Re: what grit for ground glass

    I use the 400 and 600.

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    Re: what grit for ground glass

    I ground one last night with the 400 and it looks beautiful. I think the only way to get my answer will be grind another with 800 and compare them on the camera. But I am debating whether to just use 800 for the next one, or start with 400 and finish with 800.
    Science is what we understand well enough to explain to a computer. Art is everything else we do.
    --A=B by Petkovšek et. al.

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    Re: what grit for ground glass

    Most glass isn't flat, and so the first step is to flatten it. It's flat when there's an even scratch pattern across the screen. Rinse all the grit off of the grinding surfaces, and continue with finer grits until you get the level of diffusion/granularity that you want. You can start with the finest grit right away, but it'll take much longer to flatten the glass.
    May tomorrow be a better day.

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    Re: what grit for ground glass

    +1 what Peter said. Yes, you can start with a very fine grit, but ya better grab a pot of coffee and settle in because it's gonna take ya awhile!

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    Re: what grit for ground glass

    I don't know how the grinding grit equates, but I always just use the medium Aluminum oxide grit size, .0002. I don't try to polish the glass flat, I don't care if it's not flat and don't note any patterns when I start from clear and go to .0002 directly. I do notice that the Alum Oxide makes very fine screens, where as a lot of home made ones with the carbide grinding compound seem to have huge micro-divits in the glass....that look like a bunch of clear craters, under a loupe. With the carbide, chips of glass flake out like what happens to flint when making an arrowhead.

    Here is the reference I learned from, I believe: http://www.dokasphotos.com/techniques/ground_glass/

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    Peter De Smidt's Avatar
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    Re: what grit for ground glass

    I use 3 micron aluminum oxide for the final finish. If the glass is not flat, then the granularity of the screen will not be even. For instance, I recently started grinding a 4x5 screen using aluminum oxide. After 1/2 hour the edges were done, but there was a clear strip down the middle do to the glass not being flat. Grinding recommenced until the glass was evenly ground.
    May tomorrow be a better day.

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    Tim Meisburger's Avatar
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    Re: what grit for ground glass

    Interesting article Garrett. The ground glasses I have made recently using the 300 and 600 are quite coarse under the loupe. Seems I need to switch to aluminum oxide. Where did you buy it?

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    Peter De Smidt's Avatar
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    Re: what grit for ground glass

    Lortone.
    May tomorrow be a better day.

  10. #10
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    Re: what grit for ground glass

    This place sells a variety of grinding compounds:

    http://www.willbell.com/atmsupplies/atm_supplies.htm

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