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Layla Nahar
10-19-2014, 11:19 PM
Hi,

I'm looking for a general answer - if you have three objects, say a cup, of the same size, would the heaviest be bronze, the next heaviest iron, and the lightest, steel? ETA: Oh - and how much heavier would an identical cup of gold be than the heaviest from above? - twice, three times the weight? Also, with bronze vs iron and aging - say you had a bronze object and an iron object (assume identical objects)lost/forgotten in the same environment, same amount of time, is it the case that bronze would get a patina, and detail like scrollwork or inlay would remain fairly visible, but with iron rust would consume/obscure and/or destroy detail and complex working?


thanks very much -
LN

Bolero
10-20-2014, 12:35 AM
For your weight question, look up the density. If they are all the same size, the ratio of the weights would be the same as the ratio of the density.

On your detail question, I don't know, but would suggest looking at pages on archealogical digs and restoration of objects.

In terms of the oxidation of the three metals, how much they are degraded will depend a lot on the environment. Also on the type of steel. Not all steel is stainless.

King Neptune
10-20-2014, 12:37 AM
Iron
7.87 grams per cc
Bronze
8.70 grams per cc
Steel
7.83 grams per cc
Gold
19.30 grams per cc

Bronze and Steel are alloys the composition of which can vary considerably, but steel is almost always less dense than Iron. So they line up densest gold, 1 bronze, iron, then steel. The gold cup would be more than twice as heavy as the bronze cup, and the bronze would be 10.5% heavier than the iron.

There is an iron pillar in India that is centuries old but is unrusted. Pure iron rusts very little, but common iron rusts a lot. And there are many types of bronze, and some corrode more than others. But generally bronze does not deteriorate as much as iron.

Layla Nahar
10-20-2014, 01:03 AM
I
There is an iron pillar in India that is centuries old but is unrusted. Pure iron rusts very little, but common iron rusts a lot.

Oh, that's very interesting.

Thanks for the quick breakdown - I was hoping a knowledgeable person could give me a simple general answer. I started looking things up and saw that there was a lot of room for play, so to speak.

King Neptune
10-20-2014, 03:51 AM
Oh, that's very interesting.

Thanks for the quick breakdown - I was hoping a knowledgeable person could give me a simple general answer. I started looking things up and saw that there was a lot of room for play, so to speak.

The general principal is that the denser metal weighs more for a given volume than the less dense one. What are you trying to do, if I might ask.

Layla Nahar
10-20-2014, 04:41 AM
My character is holding an ancient metal vessel that is somewhat noticeably heavier than similar objects made of bronze. She's considering what it might be made of. (She is a courier for a dealer in antiquities.)(ETA - this is a fantasy & has, as expected, a pre-modern setting)

Dennis E. Taylor
10-20-2014, 04:49 AM
Eureka!

blacbird
10-20-2014, 01:16 PM
Bronze is slightly denser than iron, but it might not be a difference easily felt between objects like cups, which probably wouldn't have precisely the same volumes. Gold, on the other hand is more than twice as dense. But you'd notice gold, simply from the color (gold does not tarnish). Even lead would have a more feelable heft.

On the other hand, as you're writing fantasy, how about something like aluminum? Much lighter than iron or bronze. Or something more exotic, say, titanium? Also much lighter.

You can find lots of useful information on-line regarding the characteristics of individual elements, including densities. But, really, there are only a dozen or so metals out of which a person could sensibly fashion a cup. In addition to those mentioned, tin, zinc, nickel, cobalt, manganese, two or three more maybe. You run into problems of rarity/expense/difficulty of refining, and chemical instability. Rare earth elements (some of which aren't actually so rare), for instance, are both difficult to purify and most are reactive to oxygen or water.

But, you're writing Fantasy. You don't really need to adhere too slavishly to known chemistry/physics. Your readers don't expect that. They expect magic, in some form or another. Just like SF aficionados know that time-travel doesn't really happen in the real reality world, really. But if it makes for a good story, they're willing to set that little nuance aside, and go for the ride.

caw

Marlys
10-20-2014, 01:40 PM
My character is holding an ancient metal vessel that is somewhat noticeably heavier than similar objects made of bronze. She's considering what it might be made of. (She is a courier for a dealer in antiquities.)(ETA - this is a fantasy & has, as expected, a pre-modern setting)

To make her unsure what the vessel is made of, you could consider having it made of an alloy containing gold. The gold content could make it heavier than bronze without looking like gold. Some ideas for alloys here (http://en.wikipedia.org/wiki/Colored_gold).

Buffysquirrel
10-20-2014, 02:29 PM
Most steel isn't stainless, and even stainless steel will corrode without exposure to air.

King Neptune
10-20-2014, 04:58 PM
My character is holding an ancient metal vessel that is somewhat noticeably heavier than similar objects made of bronze. She's considering what it might be made of. (She is a courier for a dealer in antiquities.)(ETA - this is a fantasy & has, as expected, a pre-modern setting)

As has been mentioned there are many gold alloys varying widely in color, and there also are many colors of bronze. Fourteen kt gold has a density around 14, so the difference in weight wouldn't be shocking, but it would be obvious to most people. Electrum has a density in the same range as bronze, so just lighten up on the silver to make it heavier, say 25% silver and 75% gold.
http://www.goldhog.com/specific_gravity_chart_gold_metals.htm

WeaselFire
10-20-2014, 08:44 PM
Keep in mind that none of these metals is 100% pure so weights and effects will vary. Even today, there are virtually no pure gold or iron objects. Bronze and steel are already alloyed so the alloy used will determine the weight and effects.

Jeff

Bolero
10-20-2014, 10:41 PM
Eureka!

Go take a bath. :D