[CAUT] Humidity Damage

[Ed Sutton]

Patrick-

Also a valuable Journal article by Susan Graham, reprinted in the Technical Exam Source Book. 
Other shorter mentions in the Journal and in classes.
And extensive discussions on the email lists.

A discussion of the copper artist's pigments called "verdigris" can be found in Gettens and Stout's Painting Materials: A Short Encyclopedia, but it is hard to know how much this applies to what we find in piano flanges. Piano verdigris is not nearly dense enough to work as a pigment. (I used to grind my own watercolors in art school.) I don't see how the methods of historic pigment production relate to the claim that 5 weeks in 80 percent humidity can cause piano action center verdigris! 

More precisely, I almost always find piano verdigris in old Steinway parts which were apparently treated by impregnation with paraffin or some kind of oil, presumably to make the parts resistant to humidity. I have also seen it in old Mason & Hamlin wippens, though not to the extent it occurs in old Steinway parts. This would supoort Susan Graham's comments about paraffin treated action parts causing verdigris.

Paraffin impregnation has also been used to make cheaper woods moisture resistant for woodwind instruments. I once left a recorder in the sun for 30 minutes, and found it oozing wax. I have wondered if the stuff we call verdigris is really just wax that has migrated out of the flange, and if the green color is just incidental.

The European books I have don't mention verdigris. I wonder if verdigris is mainly the result of NY Steinway's attempt to make humidity resistant action parts? What are the years during which this was done? (I don't recall seeing verdigris past early 1950s vintage Steinways.) Was this treatment done in Europe or only in the USA?

It would be good to hear from someone like Ted Sambell on this!!! There are some master craftsmen whose opinions are very valuable!

Meanwhile, in Journal articles, books, classes and email discussions, I have not heard the claim (until Kevin Olsen's email on this list) that humidity causes verdigris. It may not be great literature, but it's what we got. 

Ed Sutton

----- Original Message ----
  From: James Patrick Draine 
  To: Ed Sutton ; caut at ptg.org 
  Sent: Monday, January 03, 2011 3:44 PM
  Subject: Re: [CAUT] Humidity Damage


  Hi Ed,
  And what might that literature be? A Journal article written years ago by the late Willis Snyder (and referred to many times in classes he presented) dealt with verdigris. He had several electron microscope photographs that made his point (that verdgris'd felt and even associated wood are completely compromised) rather well. Otherwise . . . I can't recall any literature, aside from assertions (pro & con) about dry cleaning fluid, ProTek CPL, zappers, etc. And elevated "common knowledge" on the lists, whispers passed down from master craftsmen, etc. 
  Bibliography, please!
  Meanwhile the non-authoritative Wikipedia has an entry dealing with non-piano verdigris which may be of interest. To quote a couple passages:
  "Verdigris is the common name for a green pigment obtained through the application of acetic acid to copper plates[1] or the natural patina formed when copper, brass or bronze is weathered and exposed to air or seawater over a period of time. It is usually a basic copper carbonate, but near the sea will be a basic copper chloride.[2] If acetic acid is present at the time of weathering, it may consist of copper(II) acetate."
  "It was originally made by hanging copper plates over hot vinegar in a sealed pot until a green crust formed on the copper. Another method of obtaining verdigris pigment, used in the Middle Ages, was to attach copper strips to a wooden block with acetic acid, then bury the sealed block in dung. A few weeks later the pot was dug up and the verdigris scraped off. One method used in the early nineteenth century had to do with reacting copper sulfate solution with solutions of lead, barium, or calcium acetate. Their sulfates are insoluble, forming precipitates and leaving the copper acetate in solution."
  And other cool information (thank you, Jimmy Wales!).


  So -- in some recognized situations -- water appears to be related to the production of verdigris.

  Patrick Draine
  Nitpicker


  On Jan 2, 2011, at 8:44 PM, Ed Sutton wrote:


    I strongly agree with Paul Revenko-Jones.
    Nothing in the literature supports the claim that humidity causes verdigris in piano actions.


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://ptg.org/pipermail/caut.php/attachments/20110103/8a5f2343/attachment-0001.htm>