Hello Friends,
I don’t post often, but read the digest every day.
Does anyone know if there is a factor that I can use to convert the
weight of a piece made in copper to find it’s weight when made in
silver.
Thanks for your help.
Marc
yes by using specific gravity of the metals.
specific gravity of copper is 8.96 and of silver is 10.5.
It is somewhat inaccurate because we work with sterling silver so
specific gravity of sterling is slightly less, but for all practical
purposes it is good enough.
The formula you can use is (weight in copper * specific gravity of
silver) / specific gravity of copper.
For example: copper item 100 grams, then (100 * 10.5 ) / 8.96 =
117.19 grams
Leonid Surpin
Hello Marc,
I found this table:
http://www.jccojewelrycastingservices.com/metal_conversion_charts
which says to multiply weight in copper by 1.16 to get weight in
sterling.
and then tried to verify it using some lower level numbers:
pure copper: 8.93 g/cm^3
pure silver: 10.49 g/cm^3
Sterling: 0.925 silver, 0.075 (mostly) copper
(percent silver)(mass silver) + (percent copper)(mass copper) =
mass sterling alloy
0.92510.49 + 0.0758.93 = 10.37
So a cubic centimeter of sterling should mass about 10.37 grams,
while a cc of copper should mass 8.93 grams… meaning the sterling
is 1.16 times more massive. Yay!
Kevin
SG of copper is 8.8-9 in book, call it 8.9. SG of silver (I assume
fine, but it’s only an estimate) in book is 10.4-10.6, say 10.5,
which is what we use for casting. Relationship is 1.18. Multiply
copper weight by 1.18 to get silver weight. This is useful for all
sorts of things, too. Divide the SG of 18kt by the SG of silver and
it will tell you a number to figure the weight of a silver piece in
gold, etc.
Does anyone know if there is a factor that I can use to convert the weight of a piece made in copper to find it's weight when made in silver.
Try:
http://www.ganoksin.com/MetalCalc
Elaine
For brass it’s multiply the object weight by 1.21 to get the weight
in sterling silver. I’d expect copper to very close to that number
too.
Thomas.
The standard density of copper is 8.92 gm/cc, and that of sterling
silver is 10.3 or 10.2 depending on the mix - say 10.3. so multiply
the weight of the copper item by 10.3/8.92 = 1.155. The density of
pure silver is 10.5, so the factor for pure silver is 10.5/8.92=1.177
Regards, Gary Wooding
I’m assuming that you’re talking of a piece of the same volume. If
that’s the case then we can look at the relative densities as though
they are masses. Therefore, if you divide the relative density of
silver (10.5 g/cm3) by that of copper (9.0 g/cm3) you get a factor
of 1.17, therefore, if you have a piece made in copper, weigh it,
multiply it by 1.17 and that will tell you roughly what it will
weigh in silver.
Helen Hill
Preston, UK
Marc-
There is indeed a conversion factor: it is just the ratio of the
densities of the metals in question. For example, if you are talking
about pure metals, a piece made in copper will be heavier by a
factor of 10.5/8.96, or 1.1719 if made in pure silver while also
using identical volumes of the metals. When considering various
alloys, the situation gets more complicated, since the mixture of
metals in an alloy affects the density.
Luckily vendors of precious metal alloys often provide the ratios for
the purpose of estimating costs. What could be tricky is the fact
that a design that works in one metal may work better using
different size components in another design. (A stiffer, stronger
alloy just requires less material than the pure and soft metal.) That
means that the density ration of the pure metals is no longer a
simple factor in relation to the weight of the finished object. Of
course if the design is something like a struck medallion, strength
is not an issue.
Dick Davies
Marc,
You ask for comparison weights of copper and silver. Well here is a
list taken from one of my trade books.
1 gram copper = 1.14 grams of silver = 1.53 grams of 14ct gold =
1.73 grams of 18ct yellow gold = 1.80 grams of 18ct white gold = 1.98
grams of 22ct gold = 2.14 grams of fine gold = 2.38 grams of pure
platinum.
A simple way to work out the weight difference between copper and
silver if 1 gram of copper = 1.14 grams of silver then it is a 14%
increase in weight.
I hope this all makes sense, the list was copied from an old Johnson
Mathey bullion book.
Regards from James Miller a goldsmith in the UK
Copper has a specific gravity of 8.9; Sterling has a specific
gravity of 10.4. (From the table in Complete Metalsmith, page 175)
10.4/8.6=1.21 (give or take a few decimal points). Multiply the
weight of the copper piece by 1.21 and you will be pretty close.
Ron Charlotte – Gainesville, FL