Info Favorites Register Log in
myArmoury.com Discussion Forums

Forum index Memberlist Usergroups Spotlight Topics Search
Forum Index > Off-topic Talk > Bronze versus Brass Reply to topic
This is a standard topic  
Author Message
Heywood Becker




Location: Carversville, PA 18913, USA
Joined: 14 Dec 2006

Posts: 1

PostPosted: Thu 14 Dec, 2006 4:20 am    Post subject: Bronze versus Brass         Reply with quote

Would you care to opine on why craftsman of old chose brass or bronze as their alloy of choice?
View user's profile Send private message Send e-mail
Nathan Robinson
myArmoury Admin


myArmoury Admin

PostPosted: Thu 14 Dec, 2006 4:28 am    Post subject:         Reply with quote

I have moved this topic to the off topic forum from the Historic Arms Talk forum. Please note that the Historic Arms Talk forum is described as "Discussions of reproduction and authentic historical arms and armour from various cultures and time periods". The off-topic forum is a catch-all for other topics of interest to this site's audience that are not specifically conversations regarding arms nor armour.

This topic is about alloys and not about a specific arms or armour item and so is best put in the off-topic forum.

Thank you.

.:. Visit my Collection Gallery :: View my Reading List :: View my Wish List :: See Pages I Like :: Find me on Facebook .:.
View user's profile Send private message Send e-mail Visit poster's website
Matthew Amt




Location: Laurel, MD, USA
Joined: 17 Sep 2003

Posts: 1,306

PostPosted: Thu 14 Dec, 2006 6:55 am    Post subject:         Reply with quote

Well, a lot depends on how far back you want to go! In the Bronze Age, zinc or zinc-containing compounds were apparently just not known, so tin was the way to go, hence bronze. The Romans seem to have started using brass (orichalcum) in the late first century BC. Interestingly, it was apparently only used for coinage and military equipment, so it's as if there was some sort of government monopoly on its use. Civilian or domestic stuff, including cookpots used by the army, continued to be made of bronze.

"Why?" As usual, that's a perilous question, unless the ancients actually write something about it. We could speculate ad nauseum about hardness and ease of working, or cheapness, or whatever, but the way the alloys varied, all of the properties and costs would vary, too. Of course there were alloys that had both zinc and tin, which in Roman stuff is often seen as a result of recycling. In other words, there was no real reason for them to add tin to a brass alloy for a particular buckle or other item, since most of the other items of that type didn't have any. When mixing up a new batch of metal, they were certainly capable of getting the alloy they wanted, but naturally recycling is more of a crap shoot.

In short, the ancients did a lot of things for reasons that we haven't figured out yet, and they all too often did them consistently or at least repeatedly. I tend to just say, "Why not?", and leave it at that, to avoid too much dangerous speculation!

Vale,

Matthew
View user's profile Send private message Send e-mail Visit poster's website
Dan Howard




Location: Maitland, NSW, Australia
Joined: 08 Dec 2004

Spotlight topics: 2
Posts: 3,193

PostPosted: Thu 14 Dec, 2006 11:21 am    Post subject:         Reply with quote

Most metallurgists think that terms such as "brass" and "bronze" are irrelevant since many alloying elements exist in most historical artefacts. Better off simply using the term "copper alloy" and then specifying the primary alloying elements involved.
View user's profile Send private message
Patrick Kelly




Location: Wichita, Kansas
Joined: 17 Aug 2003
Reading list: 42 books

Spotlight topics: 2
Posts: 5,685

PostPosted: Thu 14 Dec, 2006 11:34 am    Post subject:         Reply with quote

What do you mean by "alloy of choice"? This would indicate there were other suitable or equal alternatives, which there weren't. During its heyday bronze was the metal of choice becuase it was the state of the art in metalurgy at the time. That's why it was chosen. When other superior alternatives were developed bronze was replaced in its role as a material for warfare. It wasn't as if they had a shopping list of alternative metals to choose from that were equal in thier properties.
View user's profile Send private message
Jean Henri Chandler




Location: New Orleans
Joined: 20 Nov 2006

Spotlight topics: 1
Posts: 1,066

PostPosted: Thu 14 Dec, 2006 12:25 pm    Post subject:         Reply with quote

Patrick Kelly wrote:
What do you mean by "alloy of choice"? This would indicate there were other suitable or equal alternatives, which there weren't. During its heyday bronze was the metal of choice becuase it was the state of the art in metalurgy at the time. That's why it was chosen. When other superior alternatives were developed bronze was replaced in its role as a material for warfare. It wasn't as if they had a shopping list of alternative metals to choose from that were equal in thier properties.


Weren't there in fact quite a few different recipes for bronze / brass around though,...? At one point the Romans certainly had a choice of making things from Brass or Bronze.

For Bronze you were somewhat limited as to the sources for tin, which were (for the most part) coming down very long trade routes from ultimate sources quite far away in Spain and The British Isles. They didn't have a source of pure zinc but they made it with calamine.

I seem to remember some of the earliest "bronzes" were actually alloyed with arsenic instead of zinc or , and tghen IIRC later you had bronzes / brasses which were alloyed with arsenic (intentionally or otherwise) that made them harder. In a way thats a whole 'nother type of "bronze".

J

System D'Armes Historical European fencing in New Orleans

Essays on Hroarr

Introducing the Codex Guide to the Medieval Baltic
View user's profile Send private message
Jean Thibodeau




Location: Montreal,Quebec,Canada
Joined: 15 Mar 2004
Likes: 50 pages
Reading list: 1 book

Spotlight topics: 5
Posts: 8,176

PostPosted: Thu 14 Dec, 2006 12:32 pm    Post subject:         Reply with quote

I'm fairly sure you can make a good blade with bronze but I doubt that you can get good results with brass ?

Maybe they both can be work hardened but I've never heard of a brass razor but bronze could be sharpened enough to shave.

Many different formulas for bronze, some only modern alloy, but for cutting weapons or tools not all bronze alloys would
be useable. ( Optimum ? )

For other things brass or bronze might each have some advantages / disadvantages ?

You can easily give up your freedom. You have to fight hard to get it back!
View user's profile Send private message
Addison C. de Lisle




Location: South Carolina
Joined: 05 Nov 2005
Likes: 27 pages

Posts: 614

PostPosted: Thu 14 Dec, 2006 2:42 pm    Post subject:         Reply with quote

I think that it might be because brass doesn't hold an edge very well, but I have no idea about the edge retention of bronze or how it compares to brass...

Interesting topic Happy

www.addisondelisle.com
View user's profile Send private message Visit poster's website
Jeroen Zuiderwijk
Industry Professional



Location: Netherlands
Joined: 11 Mar 2005

Spotlight topics: 2
Posts: 740

PostPosted: Thu 14 Dec, 2006 4:22 pm    Post subject: Re: Bronze versus Brass         Reply with quote

Heywood Becker wrote:
Would you care to opine on why craftsman of old chose brass or bronze as their alloy of choice?
I mostly do bronze age casting work, so brass is then out of the question. For later period casting I still prefer tin-bronze over any other copper alloy though, first because I'm more familiar with it, and secondly because tin is non-toxic, while zinc is. IMO 12% tin bronze also has the best color. Brass just doesn't look right IMO, especially when it's oxidized it looks ugly IMO. Mind though that there's a lot of variation in brasses. I believe brass goes up to 40% zinc (high zinc brasses being a relatively modern invention), and brasses can come with or without lead added. Highly alloyed brasses have a much lower melting point, which makes casting it a lot easier. Pure tin-bronze can be quite tricky to cast, due to a higher melting point (solidifies much quicker while casting), but also because it's a fairly thick fluid, which doesn't want to flow through small openings very well.
View user's profile Send private message Visit poster's website
Bryce Felperin




Location: San Jose, CA
Joined: 16 Feb 2006

Posts: 552

PostPosted: Thu 14 Dec, 2006 6:49 pm    Post subject:         Reply with quote

I read on another site that zinc wasn't even a known element in ancient times, but often was found with copper for ready made brass in some deposits. India I believe was sort of "blessed" with a lot of copper/zinc deposits whereas Europe wasn't so much.

Tin was mostly found in Cornwall in Britain and traded a lot from there. So Bronze was pretty limited in its production compared to Iron or Copper.

I suppose you can find an atlas or Encyclopedia and find out more. I plan to do some research on this subject this weekend when I have time. ;-)
View user's profile Send private message
Matthew Amt




Location: Laurel, MD, USA
Joined: 17 Sep 2003

Posts: 1,306

PostPosted: Fri 15 Dec, 2006 7:10 am    Post subject:         Reply with quote

I've never heard of brass being used for blades, since it didn't come into use until well after decent steels were already well known. But the Romans were making brass, bronze, and iron helmets side-by-side for several centuries, so presumably they felt the protective qualities were similar enough not to matter.

Arsenic was one of the first things alloyed with copper to make it harder, but tin was better in many ways so tin bronzes took over very quickly. Oddly enough, it doesn't seem like straight copper was used much during the Bronze Age or later, probably since adding a little tin made it so much more useful and easy to work with.

Valete,

Matthew
View user's profile Send private message Send e-mail Visit poster's website
Petri Peltola




Location: Turku, Finland
Joined: 16 Mar 2004
Reading list: 10 books

Posts: 17

PostPosted: Fri 15 Dec, 2006 1:12 pm    Post subject:         Reply with quote

I've been playing around with copper alloys and ancient techniques connected to them, so I try to answer this one.

Different elements affect the properties of the metal drastically. In copper alloys the most usual ingredients have been tin, zinc and lead. Depending on what kind of material the craftsman had available and what properties he/she wanted, some or all of them would have been present in the used alloy in differing quantities. In my opinion the most important characteristics of the metal for the craftsman would have been:

-Hardness / toughness
-Appearance (colour, shining)
-Castability
-Coldworking properties (Hammering, turning, filing)

When impurities are added to copper they always lower the melting point of copper, which otherwise would be hard to achieve on a charcoal fire of a moderate size. This is the reason why they are always present on cast objects. Basically the more they added tin, lead or brass (zinc+copper) in to the crucible a) the easier it was to reach the casting temperature b) the better the molten metal would flow in to the mold.

In viking age Finland for example the cast copper-alloy jewelry has often a high lead content up to 40%. Sometimes the alloy has more zinc than lead but usually both. Tin bronzes seem to be pretty rare .

In medieval London all of these alloying elements appear, sometimes together in all sorts of ways. Sometimes there are parts made of different alloys soldered in to the same piece.

We have documents from the Roman times for different "recipes" for bronze. They used certain alloys for certain purposes, this can be seen in the studied artifacts as well as written records.

I'll go over the qualities of tin bronzes since i'm more familiar with this material.

pure copper is a red metal. It's very soft and easy to hammer cold but hard to cast.

When we start adding tin the metal becomes harder, the melting point lowers and we get better castability. The color gets to the familiar "brown" bronze color and as tin content rises the color gets lighter.

If we want to draw wire or work the metal a lot when cold (In to a sheet for example) we are usually talking of a bronze with less than 10% tin.

10% tin is the classical cast bronze, ideal for bronze tools. It can still be worked cold and work hardens to a cutting edge. It is tough enough yet hard enough.

After about 13% the bronze gets too hard and brittle to really hammer or bend but the casting properties get better.

20% tin is the classic bronze for bells. It is hard and so has a clear 'ring' to it. It still has some of that bronze color. Theophilus gives the 1/5 tin ratio for bell bronze in 'The divers Arts' from 11th century and if you buy bell bronze today you still get the same stuff, at least here in Finland.

When we go up to 25% tin we have a white metal as hard as glass. When polished I think it looks as if chromed. There's a button from 14th century London of a white tin bronze.

Zinc affects the alloy in many ways resembling tin. You just need more zinc to get the same effect and the color starts out as yellow. The patina on brass is like stained, I think thats one of the reasons why bronze is seen as "more valuable" today though the price difference isn't that big.

Lead is a very powerful element when lowering the casting temperature. It makes the color duller and is no good if you want to work the object with a hammer, but it makes filing easier(I think).

I don't know if this clarified the issue in the least. Happy
View user's profile Send private message Visit poster's website ICQ Number
Jeroen Zuiderwijk
Industry Professional



Location: Netherlands
Joined: 11 Mar 2005

Spotlight topics: 2
Posts: 740

PostPosted: Sat 16 Dec, 2006 8:19 am    Post subject:         Reply with quote

Petri Peltola wrote:
When impurities are added to copper they always lower the melting point of copper, which otherwise would be hard to achieve on a charcoal fire of a moderate size. This is the reason why they are always present on cast objects.

I personally don't find melting pure copper difficult, using a bronze age pit furnace. As long as you have a good control over the fire, it's not too difficult to get an average 1200-1300C consistantly. The only limitation I have is that the part of the furnace hot enough to melt pure copper is smaller, so I can't melt as much copper as with bronze. With pure copper, the main problem is gass absorption, which result in a porous casting. Pure copper castings are relatively rare in history, as most coppers had a few % of impurities in it (arsenic, antimony, nickel, silver). Usually for copper reproductions I add 2-3% tin, to replace those impurities, which prevents the metal from absorbing gass. With low alloyed copper, the main problem is the thickness of the liquid copper, which has the consistency of liquid honey.

Quote:
10% tin is the classical cast bronze, ideal for bronze tools. It can still be worked cold and work hardens to a cutting edge. It is tough enough yet hard enough.

After about 13% the bronze gets too hard and brittle to really hammer or bend but the casting properties get better.

Mind though that bronze age bronze usually had 10-12% tin on average plus an additional 2% additional impurities, making it harder then 10% tin bronze. I did an investigation in British bronzes (using data from various metallurgical tables). Here's a summary of the average sword alloys between 1300-800BC (Taunton, Penard, Wilburton and Ewart Park phases):



I noticed that with other artifacts, the alloy clearly varies. For swords, the tin contents is slightly lower on average, and when lead gets introduced, the average amount of lead in swords is also lower (3% average in swords, vs 6% in axes)

Quote:
Lead is a very powerful element when lowering the casting temperature. It makes the color duller and is no good if you want to work the object with a hammer, but it makes filing easier(I think).

Yep. Leaded bronze makes files etc. bite more easily, which is why it's prefered for machining nowadays. It's used in gears a lot as well, as it's self-lubricating. But that has little to do with ancient technology Happy
View user's profile Send private message Visit poster's website


Display posts from previous:   
Forum Index > Off-topic Talk > Bronze versus Brass
Page 1 of 1 Reply to topic
All times are GMT - 8 Hours

View previous topic :: View next topic
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum






All contents © Copyright 2003-2018 myArmoury.com — All rights reserved
Discussion forums powered by phpBB © The phpBB Group
Switch to the Basic Low-bandwidth Version of the forum