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Thread: Polishing to a mirror shine - problem!

  1. #1
    Join Date
    Apr 2011
    Posts
    103

    Default Polishing to a mirror shine - problem!

    Hi all,

    I keep getting a recurring problem when trying to polish silver ring shanks to a mirror shine. I am polishing by hand from 400, 600, 800, 1200 and then final polish with luxi blue and white using my Foredom.

    However, I keep getting a stripe down the middle of my ring shank where it looks like the sand paper/emery stick has not touched.

    I have tried polishing with the curve of the ring with a stick, and free holding sandpaper. I have tried going across the ring, I have tried doing a slant diagonally across!

    Every time I do it it looks like I have caught all of the silver with the sandpaper at each grade but when I go to polish if up - still have the stripe down the middle.

    The rest also looks unfinished too - so maybe I need to use further grades of sandpaper for a mirror shine?? But I am at a loss with my stripe!!

    My current ring has had 3 polishes and still does not look anywhere near mirror. I am a little scared to keep at it though as feel nervous about how much sanding you can do!

    Any ideas of what I am doing wrong???

  2. #2
    Join Date
    Dec 2009
    Location
    Central London
    Posts
    7,454

    Default

    If it is a darkish blue-grey stripe it is firescale. This is copper oxide and occurs fairly deep below the surface. The cause is too much concentrated heating with an oxidising flame (one with a sharp blue cone)

    The curse of firescale if you care about it, is that it becomes more visible the shinier you make the surface. So you can either settle for a matte finish, or keep filing, grinding and polishing until it has gone.

    These Scotchbrite polishers from Cooksons also work well for this, without being too destructive.

    http://www.cooksongold.com/Jewellery...prcode-999-ACR. Dennis.

  3. #3
    Join Date
    Apr 2011
    Posts
    103

    Default

    Arrr ok, thanks Dennis - I might have one of those in my pack of polishing bits I got with my dremmel or foredom.
    Will try this and see how it goes.

  4. #4
    Join Date
    Feb 2011
    Location
    Scotland
    Posts
    2,424

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    Could you post a picture of your stripe so we have an idea before you attack it with anything else? Is it in the same place on every ring?
    Last edited by CJ57; 19-10-2014 at 11:11 PM.

  5. #5
    Join Date
    Sep 2014
    Posts
    2,052

    Default

    I started out sanding by hand and could never get a finish I was happy with no matter how hard I tried or how many instructions I read.
    I now use the Everflex rubber burrs on my pendant motor and haven't had any problems- unless it is fire scale when I found Dennis tip about the Scotchbrite to be a great one - I used that then back to the red then green Everflex.
    http://www.cooksongold.com/Jewellery...prcode-970-360

  6. #6
    Join Date
    Apr 2011
    Posts
    103

    Default

    Thanks all - yes it is Caroline - same place - down the centre like another band! I looks like I haven't 'hit it' with the sandpaper but I have sanded every which way to try! I might try machine instead of hand - thanks for the suggestions.

  7. #7
    Join Date
    Apr 2011
    Posts
    103

    Default

    Can post photo later but at my day job today. Thanks for the help.

  8. #8
    Join Date
    Sep 2014
    Location
    Dubai (originally from Brighton UK)
    Posts
    39

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    If it is Firescale - you are better to make sure it doesn't happen in the first place, rather than try to polish it off.

    So, if you coat the item your are heating in flux (all over the piece rather than just where you are soldering) , this causes a barrier to form, and you will not get firescale. The other option is to put in pickle (acid) to remove the copper, rather than trying to polish it off.

    Hope that helps ....

  9. #9
    Join Date
    Feb 2011
    Location
    Scotland
    Posts
    2,424

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    Fire scale only down the centre seems strange, are you using binding wire to solder them?

  10. #10
    Join Date
    Apr 2011
    Posts
    103

    Default

    Hi Paul,

    I have pickled it - in Picklean warmed in a slow cooker. Left it in there for 40 mins or so. Thanks though for the help and advice - all greatly received. Will try the flux idea.

    Caroline - No - no binding wire.

    One reflection - I don't think it's fire scale it looks like scratches - like the sandpaper has not hit it but as I said - sanded three times and every which way I can with different grade?!

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