[Jewelry making - Article 00071] - Re: [Orchid] Utility Sink, Hard or Soft Water?

[John Burgess]

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>     Hello Glenn and calling on John Burgess, 

    You Rang, Modom? 

>             A random thought occurred to me in regard to using
>     softened water for mixing investment.  John Burgess should probably
>     give us his opinion on the chemistry here.  Nothing was mentioned
>     about the method of water softening.  Is this a home water softener
>     that uses salt? 

    G'day; The 'hardness' of water is caused either by the presence of
    calcium carbonate, (permanent hardness)  or bicarbonate. (Temporary
    hardness)  The word 'hardness' refers to difficulty of obtaining a
    lather with ordinary soap.  (Sodium stearate) Because of the presence
    of salt (sodium chloride) in sea water, that cannot give a lather
    with ordinary soap.    Thus, I find it difficult to understand how
    the addition of salt to hard water can possibly soften it.  

    I'll digress slightly by saying that soap is made by boiling caustic
    soda (sodium hydroxide) with beef fat (stearic acid) which produces
    soap (sodium stearate)  If the resultant liquid is poured into salt
    solution the soap is precipitated, leaving unreacted fat behind. The
    soap is filtered off, washed, and pressed into blocks. 

    Water can be softened by the addition of ammonia or washing soda,
    (sodium carbonate) These soften the water by the addition of hydroxyl
    ions (OH) which help soaps lather well.  

    The industrial  way of softening water is to pass it over certain
    ion exchange resins, which remove all calcium, and can indeed remove
    most metals, even sodium and potassium.  The natural zeolites which
    are a type of clay-like rock will also remove calcium hardness. 

    Now I know about Calgon, but confess that I have no idea what it
    consists of, but I do know that it softens water effectively. >     If
    the water is softened by a home softener using brine, the >    
    hardness is lowered by replacing the Ca and Mg with Na from the >    
    brine.  John, would that higher Na level in the water affect the >   
     investment set-up in some way? 

    Like I said, I cannot see how the addition of brine can soften
    water.  I know very little indeed about casting investments, and can
    offer no real information,  but I suspect the presence of salt might
    retard the hardening of an investment.  But I don't KNOW!   (There's
    an awful lot I don't KNOW!) -- Cheers for now, John Burgess;  
    johnb AT ts.co.nz of Mapua Nelson NZ 

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