Verdigris (Was Re: further clarification on query)

[CA]

Jim Coleman, Sr. wrote:

> Hi Tim:
>
> It has been my experience that I have seen verdigris only on one brand of
> pianos. This manufacturer for many years treated its bushings with a
> paraffin solution. It was a nice lubricant until it began eating away
> at the plating of the center pins and when it got to the brass it turned
> green (the verdi part of the word)
>
> Jim Coleman, Sr.
>
> PS If I'm wrong about the only brand, please correct me. I've been corrected
> before and have survived. JWC
>
> On Wed, 11 Feb 1998, Tim Keenan & Rebecca Counts wrote:
>
> > List--
> >
> > I should go and look at the archives, but my resources describe verdigris
> > as principally copper sulfate, with minor components of other salts. The
> > reaction happens everywhere copper is exposed to air containing sulfur
> > dioxide (SO2)[everywhere on Earth, to a greater or lesser degree, but
> > more near coal-burning power plants and active volcanoes] , but will
> > proceed faster in humid air where SO2 becomes H2SO3 (sulfurous acid) in
> > aerosol form.  It also forms as a result of contact with
> > sulfur-containing acids on skin.  It cannot form if the copper doesn't
> > come in contact with an acidic sulfur compound.
> >
> > It occurs to me that prophylactic use of Protek or a similar product
> > which leaves a PTFE film a couple of molecules thick on the copper
> > plating of the pins ought to go a long way to preventing the accumulation
> > of verdigris in the first place. If pins were "Protekted" when new, and
> > occasionally thereafter, perhaps the problem could be greatly reduced.
> >
> > I also notice that it doesn't seem to be directly related to age--perhaps
> > some bushing cloths use sulfuric acid as a mordant in the dyeing process
> > and it isn't always entirely washed out? I've seen pianos of virtually
> > identical ages but different makes (circa 1905) in a church in Hamilton,
> > Ontario (major steel manufacturing centre with coke ovens and stuff--lots
> > of SO2) where one piano had no problem and the other was quite gunked up.
> >
> > Whaddya think?
> >
> > Tim Keenan
> > Noteworthy Piano Service
> > Terrace, B.C.
> >