Ebony bridge caps

[David Love]

They might have used denser boxwood in the treble to compensate for the
increased bearing and shorter speaking and backscale lengths which, during
expansion, would put a greater amount of compression stress on the cap from
the strings.  

David Love
davidlovepianos at comcast.net 
www.davidlovepianos.com

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of John Delacour
Sent: Monday, June 04, 2007 12:53 PM
To: Pianotech List
Subject: Re: Ebony bridge caps

At 10:32 am -0700 4/6/07, David Love wrote:

>I can't imagine it would have any effect on sound.  A cap less prone 
>to expansion and contraction and which resists string indentation 
>would be the primary goal for selection of material.

I think that is definitely a secondary consideration.  If it were 
not, why would makers not have continued the capping in the denser 
wood (normally boxwood) the whole length of the bridge?

The relative density of European boxwood is from 0.95 to 1.1, that of 
maple 0.63, of beech 0.72.  Boxwood is denser even than most of the 
rosewoods and has the advantage of being free of visible pores and 
blending in colour pretty well with the rest of the bridge.  The use 
of boxwood rather than the hardest of  woods, such as ebony and 
lignum vitae (say 1.2 g/cc) will make less difference than using 
maple rather than beech.  The audible gain from using the dense 
capping diminishes as one goes down the scale, at which point makers 
mitre it off and continue with the solid bridge.

I think I recall correctly when I say that Fazioli and Steinway 
Hamburg cap the treble with boxwood, as do, or did, countless other 
makers.  I am pretty sure that simple experiments would show a marked 
difference in timbre between the bridge capped with boxwood (or 
ebony!) and the plain bridge.

JD