S&S D --BROKEN SOSTENUTO STIRRUP

[Horace Greeley]

Dave, et al,

Silver soldering is preferred for a large number of repairs like this, but
differs somewhat from standard lead/tin work.

I use a "craft" torch, which is a hand-held, naturally aspirated torch.
Mine is a Victor (like the welding stuff), and will work with a variety of
gases.  Normally, I use MAPP gas, rather than acetylene or LPG/CNG, as
MAPP, being heavier than air, sinks to the floor, and is thus easier for me
to dissapate  (given the way my workspace is set up).  Also, MAPP is nearly
as hot as acetylene, but burns with fewer hydrocarbon byproducts, so
introduces less joint-weakening contaminents into the joint.

After carefully cleaning  and fitting the joints, then heat the _larger_
and/or more massive workpiece _first_.  When it is hot enough so that the
liquid flux dances on it (the way water does on a griddle that is ready for
pancakes), then apply small amounts of solder, watching to see how it
behaves.  If it flows well into the joint and forms the small, concavity
Bob Davis spoke of, give it just enough solder to be sure it has flowed
evenly around each piece to be soldered, then move the flame away.

This takes a little practice.  I am not sure I would recommend starting out
on sostenuto rods - dead action frames maybe.  (Although they should _not_
be silver soldered in practice as the process generates enough heat to
damage the core wood.)

Most good welding primers also have a section on silver soldering.

Best.

Horace



Horace Greeley			hgreeley@leland.stanford.edu

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