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--></style><title>Re: Fw: Bridge caps: box wood vs
maple</title></head><body>
<div>Roger, Dale and list,</div>
<div><br></div>
<div>The boxwood you are referring to is<i> Buxus sempervirens</i>,
which is a Roger says much harder wood than Maple<i> Acer
saccharum</i>.</div>
<div><br></div>
<div>Species<x-tab>
</x-tab><x-tab> </x-tab>Air
Dry Density (ADD)</div>
<div><br></div>
<div>Maple<x-tab>
</x-tab><x-tab> </x-tab>0.73
gr/cc</div>
<div><br></div>
<div>Boxwood<x-tab> </x-tab>0.9 gr/cc</div>
<div><br></div>
<div>I prefer to rate timber density in grams per cubic centimeter,
since water has a density of 1.0 grams/cc. This makes understanding
the relative densities straightforward. Wood substance has a basic
density of 1.5 gr/cc. The wood substance in the lightest hardwood
Balsa ADD 0.2gr/cc to the heaviest hardwood Yarran ADD 1.3 gr/cc is
the same at 1.5 gr/cc.</div>
<div><br></div>
<div>As Ron N and Roger mentioned, Boxwood is now used for the top
treble sections of Yamaha C series grands. Fazioli uses Boxwood for
the top section, then Hornbeam for the next, and then maple for all of
the lower string sections.</div>
<div><br></div>
<div>Steinway Hamburg used Boxwood for the two upper treble sections
until sometime in the 1980s. They now use maple for all Hamburg
Steinway bridge caps. Several earlier Hamburg pianos through the 60s
and 70s with Boxwood caps had problems. I noticed that the Boxwood
they used was often inappropriately cut on the cross, or even slab cut
in some cases.</div>
<div><br></div>
<div>Boxwood is so fine its difficult to determine the grain direction
by just physically looking at a bridge cap. But its pretty easy to see
when an old cap is sawn through.</div>
<div><br></div>
<div>I've often wondered why Boxwood bridge caps are prone to failure,
but there are two factors on my short list of suspects.</div>
<div><br></div>
<div>Firstly, with a density of 0.9 gr/cc, these caps would require a
much larger drill than a maple cap to avoid excessive internal
pressure. We use a drill 94% of the pin size for new maple bridges.
This percentage would almost certainly split a boxwood cap.</div>
<div><br></div>
<div>Secondly, for some years now I have suspected that the black slip
coating which is applied to most bridges may lead to bridge damage in
commercial usage, when subjected to high intensity lighting. The
higher density Boxwood would be more prone to thermal damage than the
lighter rock maple.</div>
<div><br></div>
<div>Regards,</div>
<div><br></div>
<div>Ron O</div>
<div><br></div>
<div><br></div>
<div><br></div>
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