I noticed 'same crucible'. in your post that i quickly skimmed...
therein lies the proverbial rub..use different crucibles for
different metals..always mark what's in them and clean and recoat
with flux when colored oxides build up in the glassy spent flux. A
remedy you can also try to use: combine sal ammoniac and charcoal
powder ( sal ammoniac is available at stained glass supply stores in
a handy cube really cheap) to purify the alloy, air cool, then remelt
in a cleaned and relined or simply different (if not open torch
method) crucible and then use regular flux( borax/and a bit of salt
petre for Au and just borax +boric acid for Ag) while remelting and
pouring the ingot that may clean it well enough to yield a nice
bright ingot that will anneal and roll smoothly.
Possibly use a digital scale (particularly as you get older and eyes
go as opposed to an assayists scale) and write everything down so
you can trace your steps when beginning to alloy with expensive
precious metals. I mark open melt crucibles, graphite or
composite/clay bound or fused silica with an heat proof / ultra-high
temp conductive silver paint pen as is available at some electronics
dealers (radio shack for example- the same pen is great for primitive
electroforming ! ), or simply notch rather shallow marks in the
crucible's bottoms to denote the dedicated metal that each will hold.
I have managed to save that first ingot of gold I ever poured and
learned basically the same lesson on mixing crucibles, or rather not
to, with. It is a fascination that stirred me to alloying as one of
the many passions involved with jewelry making..
There is a book I highly recommend by Harold O'Connor, entitled, "the
Jeweler's Bench Reference". though out-of-print it is still fairly
widely available for under twenty dollars and is almost invaluable
in the shop for those calculations, formulas, and measuring devices
among other things that we tend to forget without a handy reference,
in a handy format- which is what this little high mil black vinyl
covered spiral bound book is. You should get one. ( if you want one
but can't find it conveniently, write me off Orchid and I can help).
As for the gold boiling out of solution i'm not certain what you
mean, but i have only lost gold in aqua regia solution not a melting
furnace, muffle, or crucible- although i used to come up with some
strange tough alloys that i attributed to contamination by steel
bits from saw blades or files, etc, in scrap reclaimation once upon a
time, until i discovered the ease of magnetism in removing those
micro-bits from my sweeps and scraps and filings.
..and an aside to those of you who dislike my arcane uses of chemical
terminology..too bad! that's what I know, that's what I call them,
that's what I look for in off- the- beaten --path --stores ( and
probably why I pay a lot less than most for items -because many don't
recognize that the quarter pound $1. 35 sal ammoniac block in a
stained glass supply store used for cleaning and tinning a soldering
iron is the same sal ammoniac, or Ammonium Chloride/ NH4Cl used for
centuries by goldsmiths for purifying metals and alloys and sold as
Ammonium Chloride at a much higher price, per oz., by large supply
houses that many jewelers and hobbyist metalsmiths rely on)..and I
don't intend to rethink how I phrase my chemical terminology for the
sole purpose of posting on Orchid at this point in my life, -
alchemy and archaic woodcuts of 'the jewelers shop' c. 1300's is what
attracted me to jewelry making in the first place, thank you..
R. E. Rourke