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

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

0.925*10.49 + 0.075*8.93 = 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:

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