Notices
Results 1 to 6 of 6

Thread: Chemically Polishing Corundum

  1. #1 Chemically Polishing Corundum 
    Forum Bachelors Degree Kerling's Avatar
    Join Date
    Jul 2012
    Location
    Copenhagen
    Posts
    440
    Hello everyone,

    I have problem, I want to polish a Synthetic Ruby, I however (obviously) have nothing harder and I can't really make it shiny. It has a haze on one side, and thought that by keeping it under a flame would deposit fine carbon on the microspikes. So that afterwards I'd put it in a chlorine solution with a little bit if HCl acid. But, nothing happens. Does it require a high activation energy or something? Or is it just really slow?

    Any helps of a chemists (preferably one that has some degree) would be greatly appreciated!
    Regards,
    A theoretical physicist.


    In the information age ignorance is a choice.
    Reply With Quote  
     

  2.  
     

  3. #2  
    Life-Size Nanoputian Flick Montana's Avatar
    Join Date
    Jul 2012
    Location
    Flatland
    Posts
    5,437
    I polished a corundum sample with some high grit diamond sandpaper. Not sure about doing it chemically, though.


    "Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us." -Calvin
    Reply With Quote  
     

  4. #3  
    Forum Isotope
    Join Date
    Feb 2012
    Location
    Western US
    Posts
    2,857
    Quote Originally Posted by Kerling View Post
    Hello everyone,

    I have problem, I want to polish a Synthetic Ruby, I however (obviously) have nothing harder and I can't really make it shiny. It has a haze on one side, and thought that by keeping it under a flame would deposit fine carbon on the microspikes. So that afterwards I'd put it in a chlorine solution with a little bit if HCl acid. But, nothing happens. Does it require a high activation energy or something? Or is it just really slow?

    Any helps of a chemists (preferably one that has some degree) would be greatly appreciated!
    Regards,
    A theoretical physicist.
    I am certainly not a chemist, so I asked one down the hall to take a look at your question. She doesn't have direct experience with ruby, but suggests a chemical-mechanical polish using phosphoric acid and an abrasive slurry of corundum. She noted with a smile that her advice is worth every penny you paid for it.
    Reply With Quote  
     

  5. #4  
    Forum Sophomore
    Join Date
    Jan 2014
    Posts
    106
    Corundum will dissolve a little in strong sodium hydroxide solution, heated. A nickel vessel would be suitable to hold the solution. You would need to experiment with the time.

    You might even need to use a molten caustic bath. Diamonds are polished using a molten mixture of sodium hydroxide and sodium nitrate. Be prepared that the reagent may attack different crystal faces at different rates.
    Last edited by Warron; January 22nd, 2014 at 10:17 PM.
    Reply With Quote  
     

  6. #5  
    exchemist
    Join Date
    May 2013
    Location
    London
    Posts
    3,414
    Quote Originally Posted by Kerling View Post
    Hello everyone,

    I have problem, I want to polish a Synthetic Ruby, I however (obviously) have nothing harder and I can't really make it shiny. It has a haze on one side, and thought that by keeping it under a flame would deposit fine carbon on the microspikes. So that afterwards I'd put it in a chlorine solution with a little bit if HCl acid. But, nothing happens. Does it require a high activation energy or something? Or is it just really slow?

    Any helps of a chemists (preferably one that has some degree) would be greatly appreciated!
    Regards,
    A theoretical physicist.
    I'm not at all sure that chemical reactions are the way to go. You may get etching rather than polishing.

    I see from the web that commercial gem polishing is done by abrasion not chemistry: How are Gems Cut and Polished?
    Reply With Quote  
     

  7. #6  
    Forum Sophomore
    Join Date
    Jan 2014
    Posts
    106
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by Kerling View Post
    Hello everyone,

    I have problem, I want to polish a Synthetic Ruby, I however (obviously) have nothing harder and I can't really make it shiny. It has a haze on one side, and thought that by keeping it under a flame would deposit fine carbon on the microspikes. So that afterwards I'd put it in a chlorine solution with a little bit if HCl acid. But, nothing happens. Does it require a high activation energy or something? Or is it just really slow?

    Any helps of a chemists (preferably one that has some degree) would be greatly appreciated!
    Regards,
    A theoretical physicist.
    I'm not at all sure that chemical reactions are the way to go. You may get etching rather than polishing.

    I see from the web that commercial gem polishing is done by abrasion not chemistry: How are Gems Cut and Polished?
    On reflection, I think you are right. Chemical polishing is a very specialised technique which can give some great results, but it isn't something for a one-off project.

    And of course there are things harder than ruby.
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •