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  • jpisc98357@aol.com
    Dear Friends, Antonio deMelo in Lisbon Portugal was kind enough to send me a link to this article on bronze disease. Please book mark it for future use.
    Message 1 of 1 , Nov 1, 2002
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      Dear Friends,

      Antonio deMelo in Lisbon Portugal was kind enough to send me a link to
      this article on bronze disease. Please book mark it for future use.<A HREF="http://minelabowners.com/conserving.html"> Click
      here: HOME</A>
      Conserving Copper-Alloy Objects
      > see also:<A HREF="http://minelabowners.com/coincleaning.html">
      > Coin Cleaning</A>
      > <A HREF="http://minelabowners.com/cleaningbronzeroman.html">Cleaning bronze and Romana</A>
      <A HREF="http://minelabowners.com/cleaningcoppercoins.htm">Cleaning Copper</A>
      <A HREF="http://minelabowners.com/conserving.html">Conserving</A>
      <A HREF="http://minelabowners.com/coincleaningadvanced.html">Advanced Cleaning</A>
      Many copper-alloy objects will remain stable when excavated, and will require
      no particular conservation treatment. The application of waxes or lacquers as
      mentioned previously may however aid protection as well as improving the
      appearance of an object. One of the most destructive threats to copper-alloy
      objects is a condition known as bronze disease'. This can he recognized by
      small areas of powdery green corrosion, which erupts from below the surface
      of an object. This is caused by the presence of chlorides which were sealed
      within the corrosion products. And which can become active if the environment
      of an object is altered. This may also occur when an object has been
      subjected to chemical or electrolytic cleaning. Once it takes hold, bronze
      disease is a progressive form of corrosion, which, if left unchecked, can
      totally destroy an affected object. The only solution is the removal of the
      affected areas. This can he achieved either by totally stripping an object
      hack to hare metal, with all its attendant disadvantages. Or by picking out
      any small spots with a dental tool or adapted engraving tool. If any trace of
      bronze disease is left, it will re-occur. To conserve an object, either
      following the removal of bronze disease or after any form of cleaning and/or
      toning, treatment with benzotriazole (BTA for short) is now generally
      recommended. Before using BTA, an object must first be degreased by Immersion
      in alcohol or acetone, this should then be followed by a prolonged soaking in
      a solution of caustic soda, which will reduce subsurface chlorides and better
      prepare an item for treatment. The next step is to remove the object and
      allow it to dry, after which it should be placed in a 5% solution of BTA,
      dissolved in alcohol, It should be left for several days. Then removed and
      once again allowed to dry thoroughly. The final stage is to brush off any
      loose precipitate that may have formed, and to then apply several coats of a
      protective lacquer, preferably Incralac or another suitable proprietary
      conservation lacquer. Domestic varnishes have additives, which may be harmful
      in the long term. The BTA solution can be used repeatedly, and only needs
      disposing of once itbecomes discolored. THIS ADVICE WAS KINDLY GIVEN TO US AS

      Best Regards, John Piscopo
      <A HREF="http://www.johnpiscoposwords.com">JohnPiscopoSwords.com</A>
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