I was told that immersing a sterling piece into the pickle after
soldering lowers the melting point of the solder in that piece
and, to avoid that, you should quench in water until you are
finished soldering. I understand that repeated heating of solder
raises its melting point because the heat removes some of the zinc,
but I dont understand how the pickle would lower the melting point.
It will not affect the melting point but it is still not advisable
to quench in pickle. It will get pickle deep into areas of the work
where complete removal and neutralization is going to be difficult.
This residue can cause problems in future soldering. Also the hot
metal into pickle will put a lot more pickle vapor into the air and
may splash it over you as well.
I was also told that allowing sterling to air cool after soldering
will prevent it from becoming malleable as it does when you quench
it after annealing.
This is true but, it is not a significant difference. To get the
softest sterling after annealing you need to heat to above
1382F/750C then quench immediately.
But there are several caveats to this
almost all the silver solders are either molten or beginning to
melt (exceeded their solidus) at his temperature
it is fairly easy to fracture sterling when quenching from this
high a temperature if its crystal structure has been compromised by
improper working (over annealing is one way to do this)
So unless you have some overriding need for the absolutely softest
sterling, annealing from this high a temperature is not a good idea.
You can get very good results from annealing at 1100F/593C and be
much less likely to ruin your work.