And Charles, which one is that??? Actually bronze alloys with no
tin (and as far as I am concerned not zinc either) that are great
and consistent and do well with re-melts. I use Everdure for the
sculptural casting I do and it maintains good color well with re-
melts and welding.
90/10 definitely doesn’t look the same after a re-melt. I might be
being picky, you know where I’m coming from, but for the purpose of
the list I’ll expand my comments.
As you know alloys are mixtures of elements, this means that in the
case of 90/10 bronze, you have elemental copper and elemental tin
mixed together, they do not form another element. If they did, then
re-melting the alloy would not change its colour, and more
importantly there’d only be one recipe for bronze.
As it is when you heat a piece of 90/10 bronze the tin will
vaporise, and go elsewhere (brass is the same except using zinc and
copper), leaving a greater portion of copper.
I notice a colour change when I re-melt 90/10 bronze (I’m picky). In
fact if you keep re-melting the same bronze over and over again, in
the end you’d be left with copper.
This is not new this has been known about for
centuries. People doing re-melts in the past have had to add extra
tin to maintain the colour. Also in the past, if tin was not
available, then whatever was on hand would go into the re-melt.
Tin vaporising is an awful waste, zinc vaporising is really
dangerous, and will make you quite ill, if not kill you.
Any bronze that is re-melted will lose some of the lower melt point
elements, and colour changes can be noticeable. If alloying bronze
made an element then it wouldn’t change colour when remelted, it
would simply oxidise.
I even use this to my advantage if I want to make a faux gold. I get
a nice piece of brass, and re-melt it, some of the zinc evaporates
and you’re left with a different coloured alloy.
Let’s get a little more into the alloy recipes :-
Everdure Bronze, this is a trade name for a silicon bronze, which
technically isn’t a bronze at all (bronze needs tin in it to be a
true bronze). The alloy recipe for Everdure is 95% Copper, 4%
Silicon, and 1% Manganese. Copper is 1083C (1981F), Silicon is 1420C
(2588F), and Manganese is 1245C (2273F).
90/10 bronze, or ancient bronze, or Anglo-Saxon bronze is 90% copper
and 10% tin. As before Copper has a melt point of 1083C (1981F), and
Tin is 232C (450F).
The melt point of 90/10 bronze is greater than that of tin, so when
heated the tin turns to a vapour.
The melt point of Everdure varies with the alloy (there’s always a
plus or minus with industrial alloys). If the melt point of the
Everdure alloy is less than the lowest melt point element, then the
colour will not change. If the melt point is higher than the lowest
melt point element (and sometimes it just has to be), the colour will
change.
I hope that make sense, if not I can always answer questions
Regards Charles