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    Re: sextant replacement mirror
    From: John Huth
    Date: 2010 May 4, 13:36 -0400
    George - 

    Robert E. White


    fixed up my sextant for me.   On the other hand, it sounds like a fun project if you want to do it yourself.

    John H. 

    On Tue, May 4, 2010 at 12:26 PM, Douglas Denny <douglas.denny@btopenworld.com> wrote:

    Or, I'll silver it for you - so long as it is a 'one-off' - to get another dead sextant into good working order. (I do not want to be inundated with requests to silver mirrors).

    Silvering is quite easy so long as you have the materials and are careful with cleaning the glass surface. It is based on Brashear's method.(or Tollen's reagent - similar).

    You need:- silver nitrate; conc.(0.88) ammonia solution; glucose; sodium hydroxide; de-ionised water.

    and for cleaning: degreasing solvents: eg; carbon tetrachloride; methyl ethyl ketone; acetone; conc. nitric acid.
    best if possible: finishing with conc. sulphuric acid and potassium dichromate solution.

    I'll describe the method and concentrations of solutions if anyone requests it.

    Douglas Denny.
    Chichester. England.

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