Alloying bronze for casting

Jewelry Discussion
41 
Bell metal is about the hardest bronze there is, which gives it
good resonance. Drop a brass disk (or a quarter) on the floor and
hear it ring. Drop a pewter disk and hear it go "thud". And yes
it's brittle in the sense that if you hit it with a sledge hammer
it will break rather than bend.

Sounds like one of the silver/copper alloys could do. A more, er,
unmalleable alloy than stg like 500sil (50/50) which is quite
springy.

Brian
Auckland
New Zealand
www.adam.co.nz

42

I made a couple of silver bells for people in London. They sounded
fine, but I was not asked to asked to tune them, the customers were
very happy. With silver bells and cockle shells and pretty maids all
in a row. You will have a queue at your door! HA HA

David Cruickshank (Australia)
jewellerydavidcruickshank.com.au

43

Hans, thatā€™s a super ā€œhow to do itā€ on making a bell out of silver!
Iā€™m going to have to try that. So ā€œsilver bells, itā€™s Christmas time
in the Cityā€, can be made out of true silver. Though, from what so
many others are saying the best tones will still be obtained from
bell bronze. Maybe Iā€™ll have to try that, too. Adding sound to my
jewelry - sounds like fun. And plenty of time til next Christmas to
get 'em ready!

Denny Turner

44 
Though, from what so many others are saying the best tones will
still be obtained from bell bronze.

Making a bell with pleasant tone is not as simple as it may appear.
Consider the following: Fundamental frequency will be defined by the
edge of a bell. This frequency will produce harmonics which are
multiples of fundamental. Area next to the edge, which is of smaller
diameter will have itā€™s own sound, slightly higher than fundamental,
and so on. For every decrease in diameter a frequency will be shifted
upwards, and every frequency will have itā€™s harmonics. The total of
all these frequencies is the sound of the bell.

Humans react negatively to odd harmonics and positively to even
ones. 5th harmonic is especially bothersome. The task of bell
designer is to control odd harmonics by the shape of the bell.

Than we have to consider decay rates. The longer the decay rate, the
more of property which we call ā€œsilver bell soundā€, but longer decay
rates require more mass, and correct mass distribution throughout
bell body. In this respect, designing a bell is akin to designing a
violin.

Bell metal is the best alloy for percussion sound generation, but it
is not easy to work with. It is a great project to make a bell, but
do not take it lightly. Study the subject before you start.

Leonid Surpin

45

Iā€™m going to cast a small turtle carved in wax, and was wanting to
casting it in bronze that I can patina green. My questing is what
would be the best alloy of bronze to use to cast it in that would be
easy to patina green, and the best method to get a green patina in
the finished piece? Iā€™ve never alloyed my own bronze or colored with
patinas other than liver of sulfur, and I would like to learn how I
would go about doing it. Also what would be the best sources of
copper and tin to alloy together?

46

Hi Don,

I'm going to cast a small turtle carved in wax, and was wanting to
casting it in bronze that I can patina green.

The elements copper and tin are best sourced from a metal merchant,
I get mine from industrial metal suppliers, and they are pure. I buy
the tin in chunks, and the copper in granules.

What is the best alloy, is the one you like, or the one your
customer wants. The silicon bronzes, and silicon brasses seem to be
more forgiving when it comes to remelts (as has been reported in
previous discussion regarding bronzes), than a 90/10.

If you want to personally recycle the copper and tin yourself, as
opposed to buying it, you will be spending a little time skimming
dross off your melt, but the results can be the same.

Patinating, Iā€™ve normally let the pieces I make self patinate over
time, but if you want to hurry it along, there are plenty of recipes
for patination chemicals on the net.

Hereā€™s one but there are more out there :-

Kindest regards Charles A

47

I have been using an alloy from Japan called Shibuitsi which is 25%
sterling and 75% copper. It takes a wide range of navigation and has
a lovely iridescence.

1 Like
48

Hello Don,

Check out my blog, I know the topic is about brass and not bronze
but the basics are the same.

http://www.ganoksin.com/gnkurl/x0

I hope this helps.

As far as a patina for bronze, I like to use two liquids. First a
soda pop dip. After you dip the item let it fully dry before
repeating or going to step two. Second a flat salty soda pop (I add
salt) sprayed on the surface. What you want is to mist the liquid on,
donā€™t soak the surface, you want it to evaporate off fast.

When the liquid evaporates this is when the patina forms. First it
will turn brown. The brown will become very matte and then in the
corners that perfect green patina will form and spread over the
entire surface in a very natural looking wayā€¦

I like doing it this way because you get the brown background first,
this makes the green color of the patina really stand out. Plus it is
natural, all you are using is salty soda pop!

There are the chemical patina solutions available but these always
leave the background blotchy. Some of the portions will remain shiny,
which doesnā€™t look right.

Anyway, I hope this helps
Kenneth