me, ma and pa each found a little something today

[ThatCannonballGuy]

Steve, thank you for taking the time to provide that photo. : )
To my eyes, those tombac buttons look a "light-copper" color. It's what I previously though tombac always looks like. Because of this discussion-thread, I now know that tombac which contains a higher-than-usual percentage of zinc will look silvery instead of coppery/brassy.

Viewing your buttons, I can see why tombac was so popular prior to about 1800.

Regards,
TheCannonballGuy

 

[Steve in PA]

Most of the "tombac" buttons I find are dull grey to silvery grey. These are some of my nicer engraved ones, but most are plain.

 

[ThatCannonballGuy]

Steve, just an FYI...

This thread has caused me to do a lot of research on the actual "elemental composition" of the metals in the buttons we dig up.

It turns out that:
ANTIQUE pewter is an alloy containing mostly tin, with a high lead content, plus "about" 2% copper, 2% antimony and/or bismuth.
MODERN pewter is mostly tin (90% or so), but no longer contains any lead (due to toxic hazard).
Britannia-metal is "related" to pewter, being also mostly tin (92%), but with 6% antimony (and 2% copper).
Tombac is an alloy containing mostly copper, with some zinc (the "golden-looking" 1942-43 Canadian tombac 5-cent coin is 88% copper with 12% zinc).
Brass is an alloy containing mostly copper, with anywhere from 20-to-40% zinc.
Bronze is an alloy containing mostly copper, with some tin. (For example, what Richmond's Tredegar Foundry called "gun-metal" is 88% copper, 10% tin, and 2% zinc.)

That's probably more info than anybody was interesting in hearing, But my main point (regarding the buttons in this thread) is this:
Late-1700s buttonmakers came to regard Britannia-metal as being superior to pewter because (unlike pewter) it KEEPS its "silver-ish" shinyness. It DID NOT CORRODE (like pewter buttons obviously do). So, that's how we diggers can tell the difference between a britannia-metal button and pewter button.

Another sign of a britannia-metal button is the "spin-marks" (similar to lathe-marks) often visible on the button's back side. Pewter was too brittle to spin/lathe.

Regards,
TheCannonballGuy [Pete George]

 

[ma and pa diggins]

I think you should change your name to Thatmetallurgyguy

Pa Diggins

 

[Steve in PA]

What he calls a tombac button you would call a britannia metal button. I had seen what I considered a tombac button (based on Tice's pictures) called a britannia button by archaologists, so I thought they were pretty much one and the same...

Well now I'm really confused. Most of those button I showed above are propably britannia metal (I guess).

 

[ThatCannonballGuy]

Steve in PA wrote:
"I think that Tice may have people (like me) confused. What he calls a tombac button you would call a britannia metal button. I had seen what I considered a tombac button (based on Tice's pictures) called a britannia button by archaologists, so I thought they were pretty much one and the same..."

Even professional archeologists can be mistaken when they label a metal button as being made of tombac. (They're not necessarily Metallurgists.)
This thread's discussion (and its photos) has prompted me to do some extensive research at online METALLURGICAL websites. Because of the results of that research, I telephoned Warren (Tice) and talked about this topic with him a few minutes ago.

We discussed a rather obscure variety of tombac called "white tombac" ...which is created by adding some metallic arsenic into the usual "orange" tombac alloy during the smelting process. This produced a silvery-looking tombac - known as "white tombac."

Warren also said white-tombac, like Britannia-metal, DOES NOT CORRODE (lose its shiny lustre) in the ground. So, for the moment, we're at a dead-end as to how to tell white-tombac buttons from Britannia-metal buttons. Warren did suggest I contact a friend of his who does Scanning Electron Microscope analysis of button metals. I'm going to do that.

Steve in PA also said:
"Well now I'm really confused. Most of those button I showed above are propably britannia metal (I guess)."

No, my online Metallurgical research indicates your pictured buttons are in actual fact tombac (because they are "light coppery-brassy" colored). Britannia-metal buttons are "silvery" - with basically NO corrosion or patina - and they tend to have a "spun" back side.

Regards,
TheCannonballGuy [Pete George]

 

[ThatCannonballGuy]

Pa Diggins wrote:
"I think you should change your name to Thatmetallurgyguy. : )

(Blush.) Naw, I did only what any teenager could do nowadays. I must say, Web-Searching sure is a wonderful new invention for researchers like me.)
But okay, yeah, I probably did do the Metallurgy web-research with more relentless diligence than the average American teenager would. ;-)

(still just) TheCannonballGuy [Pete George]

 

[Steve in PA]

n/t

 

[ThatCannonballGuy]

Steve in PA wrote:
"Thanks for going the extra mile to research this topic!"

You're welcome, Steve.
Because you've showed interest in the results of my research, here's some more of it for you.

One of the best metallurgical-info websites I found was at Consolidated Coin Company, a coin-MAKING company. It sells "coin blanks" - and its website at
http://www.consolidatedcoin.com/coins.htm
tells you the metal-content AND color of various alloys. (Notably, brass and tombac, among many others.)

It turns out that tombac is actually merely a type of brass. Tombac simply contains a higher percentage of copper in it than brass contains ...which causes the alloy's color to be red or "orange"/red-golden, instead of yellow.

The following info is taken from a series of "charts" at Consolidated Coin's website.

Coin-material ---------- Main elements ------------------Properties [color]
Tombac 95/5 ----------- copper 95%, zinc 5% ------------ red
Tombac 90/10 ---------- copper 90%, zinc 10% ---------- red
Tombac 85/15 ---------- copper 85%, zinc 15% ---------- red-golden
Brass 72/28 ------------- copper 72%, zinc 28% ---------- yellow
Brass 70/30 ------------- copper 70%, zinc 30% ---------- yellow
Brass 64/36 ------------- copper 64%, zinc 36% ---------- yellow
Brass 60/40 ------------- copper 60%, zinc 40% ---------- yellow
Nickel-brass ------------ copper 79%, zinc 20%, nickel 1% --golden-yellow

Hoping this info is interesting,
TheCannonballGuy [Pete George]

 

[Steve in PA]

But I'd like to know how to tell the difference between white tombac and britannia metal. A lot of the buttons I find have the machining marks on the back. Can we say with certainty that those are brittania?

 

[ThatCannonballGuy]

Steve in PA wrote:

"A lot of the buttons I find have the machining marks on the back. Can we say with certainty that those are brittania?"

In my web-research about tombac buttons and britannia-metal buttons, several sources reported that late-1700s metalworkers regarded Britannia-metal as an improvement over pewter because (unlike pewter) it could be shaped by spin-hammering and lathe-machining.

So, before my discussion with Warren Tice I'd have answered yes, we can "say with certainty that those [silvery machined-back] buttons are britannia-metal. But Warren surprised me by saying white-tombac buttons also have lathe-machining marks.

However, I am not 100-percent certain that the info Warren is relying on is correct. So I've been trying to think of SCIENTIFIC methods to test that info.

There are several scientific ways to determine a metal's atomic ingredients.
Such as:
(1) observe the metal's reaction to Oxidation (and also Acidification) characteristics
(2) check its electrical conductivity
(3) hardness and malleability/ductility (when stressed, does it bend, or slowly split, or suddenly chip/shatter?)
(4) use a Scanning Electron Microscope
Of course, #4 is linda expensive. So, I was planning to get a strong acid and compare the reaction of brass, tombac, and brittania-metal to Acidification. (That's how pawnshop-owners determine whether a metal is really Gold - or not.)

But earlier today, my good buddy Vlad sent me what might be an even easier method! He suggested using a "metal-identifying" metal detector on tne buttons.

Here is the key point:
Remember, both tombac and white-tombac are "about" 90% COPPER.
Britannia-metal is "about" 90% TIN.
So, perhaps a metal-identifying detector will be able to tell tombac from britannia-metal. Tombac should "read" in the brass/copper range, ...and britannia-metal won't.

And if that method doesn't work, I'll try the strong-acid method. I know that when a metal contains a "significant" amount of copper and you put a drop of liquid strong acid on it, the acid turns green-sih or blue-ish. But when you put acid onto Tin, the acid won't turn green.

Steve in PA also said:
"...I'd like to know how to tell the difference between white-tombac and britannia metal."

Hopefully the metal-identifying detector - or the "strong-acid" test - will enable us to do that (with scientific certainty). : )

Regards,
TheCannonballGuy [Pete George]

 

[Steve in PA]

and see if I can find some variation as to where they drop out with increasing discrimination. Maybe I can find some similar looking buttons with distict differences in conductivity?

 

[ThatCannonballGuy]

Steve in PA wrote:
"I have a lot of these type of buttons, I'll have to do some experiments ... and see if I can find some variation as to where they drop out with increasing discrimination. Maybe I can find some similar looking buttons with distict differences in conductivity?"

Vlad's other excellent suggestion to me was to use a volt-ohm-meter, to check electrical conductivity/resistance. If you're going to try that method, REMEMBER, you must put the clamps (or needle-points) on a SHINY part of the BACK SIDE of the button. This is because the face-side was often plated with another type of metal - plated not only using gold or silver, they could also use lead plating!

Regards,
TheCannonballGuy