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None of my bismuth


#1

All,

I finally relented and decided on an acetyline/air setup for joining
silver pieces rather than TIG. So now, I have a different question.

Last year, I had used bismuth, .999 pure, as a practice metal on my
CNC machine prior to machining silver, about $20 per pound. Expensive
compared to base metal but far cheaper than silver itself. I chose
the metal because it machined very easily but was also completely
non-toxic. It also does not oxidize easily, I make very nice ingots
of it with no discoloration whatever.

I have heard lots about how lead is very bad news for silver. But I
wonder what benefit I would get by creating sterling with bismuth
rather than copper. Anyone ever have experience with such an alloy?

Andrew Jonathan Fine


#2

I don’t know much about bismuth. I actually know only one thing
about it that I can think of. I have seen great ingots of it at the
Trail, BC Cominco smelter but I have never used it.

The one thing I know - Bismuth is included in the alloy for making
"type metal" , the alloy composed mainly of lead which is used for
making old-fashioned printing type. The reason for including bismuth
(I was told about 55 years ago) is that bismuth expands as it goes
from liquid to solid state, much like water ice. Therefore when the
type is cast the expansion of the bismuth insures the metal really
fills all the very fine detail in the molds as the type must be used
just as it comes from the moud - no polishing or filing is possible
after the fact. Well, actually it is possible but hardly economic.

All the edges of letters and fine points of serifs must be crisp and
sharp. I suppose this quality might have some application in casting
silver or other metals for similar reasons of achieving very good
detail - but I don’t know how much bismuth by percentage it would
take to produce the desired effect and whether that might negate your
ability to legitimately call your product “silver,” sterling or
otherwise.

Oh yeah - I know one more thing about bismuth. It is an ingredient
in Pepto-Bismol - so that speaks for its lack of toxicity.

Marty Hykin in Victoria BC who is not taking Pepto-Bismol today,
never has done, and hopes he never will.


#3

Andrew,

Point one… read the MSDS for bismuth. It is not ‘completely
non-toxic’, it might be one of the lesser nasty heavy metals but
still not good for you.

I use cerrobend (high bismuth alloy, melts at 158 F) for work holding
sometimes, any traces ignored act just like lead at subsequent
soldering operations. Easy way to make a good day into a really bad
one :slight_smile:

jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand


#4

Dear Andrew,

just about all bismuth alloys are brittle and have low melting
points. Another problem is they expand on cooling rather than
contracting and this leads to broken solder joints etc after a while
as they push themselves apart.

Nick


#5

I used Bismuth to solder Steel backs to my gravity poured Pewter
belt buckles—melts before pewter and makes a better long-term bond
than Epoxy.


#6

Jeff,

I did read the MSDS. Only thing it mentions is to be watchful of the
effects of bismuth salts rather than elemental bismuth. EPA requires
the use of elemental bismuth in place of lead for all new shotgun
pellets. Also, this from Wikipedia:

Precautions

Bismuth is not known to be toxic, compared to its periodic table
neighbours (lead, antimony, and polonium), although some compounds
(including bismuth chloride due to its corrosive acidity) are toxic
and should be handled with care. As with lead, overexposure to
bismuth can result in the formation of a black deposit on the
gingiva, known as a bismuth line.

Fine bismuth powder can be pyrophoric.


#7

As a side note, if anyone is interested in a bismuth alloy for
applications like modeling it is available in the gunsmithing trade
as Cerrosafe. Brownells has a good description at their website:

http://www.brownells.com/aspx/ns/store/productdetail.aspx?p=384

Mike DeBurgh, GJG
Henderson, NV