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  #11  
Old June 26th 09, 08:22 AM posted to rec.crafts.jewelry
Carl 1 Lucky Texan
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Posts: 57
Default Math

Peter W. Rowe wrote:
On Thu, 25 Jun 2009 19:10:41 -0700, in rec.crafts.jewelry Ted Frater
wrote:

Ill reply on the basis of memory which is still resonably reliable!.
From what I recall, there were minute ie less than .05% of arsenic and
lead in their analysis.
Now im still confused,because if the analysis is by percent, ie 9 to 10
parts of tin to 90 to 91% copper.


Why does this confuse you, Ted? It's clear enough. The ratio is slightly
approximate, Perhaps it varies from place to place in the item. But it's
between 9 and 10 percent tin, and 90 to 91 percent copper. Nothing there should
be confusing. They state there are trace amounts of arsenic and lead, but at
less than .05 percent, those easily fit into the slight variability of the
other stated percentages.

Now this has to be by volume, ie 1 part of tin to 9 parts of copper
make 100%.


Ted, you're correct that it adds up to 100 percent. But where do you get the
crazy idea that this HAS to be by volume? As we told you when you first asked,
alloy calculations and formulas are ALWAYS stated as weight percentages. It's
NOT going to be by volume. This is true not just in metals alloys, but general
chemistry too. Unless some other method of measurement is noted (moles, atomic
ratio, or a volumetric unit is used (such as liters, or cubic centimeters, etc)
weight is the standard way things are measured.

So if i start with these proportions ie, 1 part of tin to 9 parts of
copper by volume, melt them together then analyse the alloy it should in
theory come out as 10 % tin to 90% copper.


No, actually it won't. Because alloys are described by weigh percentages. If
you use volume, you'll get the wrong alloy, with not enough Tin.

Looking at it further by weight if i weigh out 1 part of tin to 9 parts
of copper, because tin is a lighter metal than copper, im going to get
more than 10 % by volume.
so when I melt and then analyse by volume its going to be more than 10 %
tin.


Please totally delete the entire concept of volume from any thinking regarding
alloy calculations. It's not used. And yes, interchanging from one to the
other does screw up stated percentages. This should not confuse you. The
methods of measurement are not simply interchangeable. Stick to weight,
consistantly, and it works. Saying that measuring by weight messes up the
volumetric ratio is talking nonsense. Yes, it's true, but it's a meaningless
observation, because the original stated measurements of the alloy are not
volumetric.

Getting back to my friend John he, im sure measured his alloy by weight,
it then would have been a bronze that was not suitable for forging into
sheet from the ingot.


The fact that he couldn't do it using his tools and working methods, no doubt
honed skills developed with other metals, does not automatically mean ancient
smiths didn't have other ways of working that alloy. Since the object exists,
and has that composition, it stands to reason that they knew how to work that
alloy, and your friend, for all his skills, apparently has not figured that out.
This should not amaze you. I've yet to meet any craftsman who actually knew it
all and could do everything, even things he/she'd not done before or had
information on doing.

As yet I dont see a flaw in my logic.


See above...

I repeat. Alloy formulats are by weight, not volume. Period.

As Abrasha pointed out, this is not just convention, it's logical. Just how
would you normally go about measuring an exact volume of a metal componant of an
alloy? Unless you'd forged it into a nice measureable ingot who's dimensions
could then be used to calculate the volume, you'd have a mess. How would you do
it with casting grain, for example? Are you really going to go to the trouble
of measuring displacement of the metal in a vessel of water? Do you think the
British Museum did that to the shield?

Using volume to measure liquids works well, since one can use calibrated
vessels. So we have liters, cubic centimeters, quarts, whatever. It's used for
liquids because it's easy and consistant. But for solids, weight is the easy
and consistant one. Measuring the volume of irregular solids, especially
multiple bits and pieces such as one might be using to mix up a batch of an
alloy, is a royal pain in the backside.. It's not done that way for that
reason.

Peter



I wonder if the piece was analyzed by X-ray Fluoresence? Perhaps that
yields a volume-type ratio? Or did they physically 'assay' a piece?

I dunno


carl
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  #12  
Old June 26th 09, 08:48 AM posted to rec.crafts.jewelry
Peter W. Rowe[_2_]
external usenet poster
 
Posts: 115
Default Math

On Fri, 26 Jun 2009 00:22:09 -0700, in rec.crafts.jewelry Carl 1 Lucky Texan
wrote:


I wonder if the piece was analyzed by X-ray Fluoresence? Perhaps that
yields a volume-type ratio? Or did they physically 'assay' a piece?


XRF analysis basically looks at the intensity of a selective spectra emitted by
the sample's surface, with any given element responding differently. With
computer processing, it then is possible to derive a quantitative analysis of
the amounts of the various elements in the surface. The basic information would
be the relative numbers of each elements atoms, so the basic yeild would be
atomic ratios, rather than either weight or volume. Volume gets tricky to
determine just from this, since the information does not give you data on
density, or on the spacing of atoms in an alloy (which can differ from that in
individual pure metals, meaning that volume, a function of density/specific
gravity versus the mass/weight, needs additional information to calculate from
just what the XRF data gives you. No doubt that could be done if needed. But
weight percentages simply need to know the numbers of each type of element or
metal's atoms, which is directly given from the XRF data. Whether the
instrument gives you results as weight percentages or atomic ratios would depend
entirely on what it's programmed to give as the results of the computer analysis
the instrument has to perform to make sense of the spectral results.

However, the subject of XRF brings up an interesting possibility, and potential
answer to Teds problem. XRF analysis only looks at the surface layers of the
sample. It doesn't penetrate much. If the sample is a uniform material, then
the result is accurate for the whole of the sample. However, if the surface
layer of the sample is NOT representative of the whole mass, then one might draw
incorrect conclusions. We all know that operations like pickling, or other
chemical leaching, can deplete some metals from an alloy surface, while
enriching others. A bronze artifact buried for a long time would be exposed to
ground water, corrosive influences, and the like. It seems quite likely to me
that the composition of the surface of the artifact might not exactly match that
of the whole mass of the metal. Whether this would result in more or less
copper or or tin at the surface, I don't know. But if XRFwas the means used to
examine the shield, it's quite possible that the published results of that
examination could have lead to an incorrect assumption as to the total
composition of the alloy. And I can imagine even that the British Museum, in
publishing those results, might simply assume that other researchers, reading
that report, would simply understand this limitation of XRF analysis, while a
craftsperson, not used to the different methods of analysis, might not realize
this limitation, and could draw the wrong conclusion...

But that's just conjecture, of course.

It's also possible they took a tiny sample, perhaps a tiny drill hole somewhere
on the thing where some repair or conservation work was already needed. Then
they'd have a better sample of the overall alloy, and the likelyhood of the
stated analysis being correct for the whole mass of metal, is higher.

Dunno either...

Peter
  #13  
Old June 27th 09, 12:56 AM posted to rec.crafts.jewelry
Abrasha
external usenet poster
 
Posts: 298
Default Math

Ted Frater wrote:
R T Smith wrote:
"Ted Frater" wrote in message
...
| Peter W. Rowe wrote:
| On Sat, 20 Jun 2009 21:32:00 -0700, in rec.crafts.jewelry Limpy
| wrote:
|
| I know there's a way to do this, but I can't remember how.
| I have x dwt's of sterling silver.
| I want to know how much that weight of sterling will weigh in 14, 18k.
| (snip)
| What I assume you want is to know what the save VOLUME of the other
metals would
| weigh, such as if you have a casting in sterling that weighs x, how much
would
| that same model, cast in another metal, then weigh.
|
| Right?
| (snip)
|
| Heres a question for you Peter,
| whilst were on the subject of alloys.
|
| My friend John Fenn is a master silver smith. Creates miracles from
| nothing with almost no tools.
| Cleverer than me by far.
| He was asked to make a replica of the Battersea shield.
| Being the determined person he is he checked out what the original alloy
| ot tin and copper was.
| According to the analysis made by the British Museum the last time they
| did a detailed study of the shield the tin /copper ratio was between 9
| and 10 %.
| So John being the person he is he tried to purchase this alloy in
| sheet form, 1mm thick.
| It is no longer made by any Co.
| So he desided to make it himself.
| No problem getting pure tin and pure copper, neither a problem for him
| to melt and cast a suitable ingot to start with.
| However often he tried he found it would become too brittle at those
| percentages to forge out into sheet despite repeated annealing.
| By reducing the tin to 6% it worked fine.
| so he and i discussed this problem of percentages of metals.
| If the analysis by the British museum was 10% tin to copper, it had to
| be by volume ie you take for example 10 1in cubes of tin and add this to
| 90 1in cubes of copper.
| However this isnt 10 % by weight is it?
| So to get the final alloy of say 10% by analysis does one go by weight
| or does one go by volume?
| Ie do you take say 9lbsof copper and add 1ld of tin to make the 10lbs or
| 100%?
| We asked IMI who list this alloy tho dont make it anymore and they didnt
| know anyone in their Co. who had the answer when we called.
| Since John had a deadline to finish the shied, for a television
| programme, I had here some 2ft by 4ft sheets of 70 /30 copper zinc I
| sent him and he made it out of that. .
| If you want to finish up with va 10% tin to 90% copper
| So what is it? ,
|
| By weight?
| or
| By volume?
|
| ted.

The individual metal constituents in an alloy are measure by weight, not
volume.
When you have a 12k gold alloy, do you think you have equal amounts in the
volume of gold and the volume of the alloying metals?

In your story, the British Museum analysis may have come up with the 9 to
10% tin/copper ratio, but did it unequivocally say that ONLY copper and tin
were in the alloy?


Ill reply on the basis of memory which is still resonably reliable!.
From what I recall, there were minute ie less than .05% of arsenic and
lead in their analysis.
Now im still confused,because if the analysis is by percent, ie 9 to 10
parts of tin to 90 to 91% copper.
Now this has to be by volume, ie 1 part of tin to 9 parts of copper
make 100%.


You are wrong, and I pointed out why.

Arguing with you is pointless.

[[moderator's edit. sentence deleted to conform with charter restrictions.]]

So if i start with these proportions ie, 1 part of tin to 9 parts of
copper by volume, melt them together then analyse the alloy it should in
theory come out as 10 % tin to 90% copper.

Looking at it further by weight if i weigh out 1 part of tin to 9 parts
of copper, because tin is a lighter metal than copper, im going to get
more than 10 % by volume.
so when I melt and then analyse by volume its going to be more than 10 %
tin.

Getting back to my friend John he, im sure measured his alloy by weight,
it then would have been a bronze that was not suitable for forging into
sheet from the ingot.

As yet I dont see a flaw in my logic.


Why am I not surprised?!?

--
Abrasha
http://www.abrasha.com
  #14  
Old June 27th 09, 05:52 PM posted to rec.crafts.jewelry
ted frater
external usenet poster
 
Posts: 133
Default Math

Abrasha wrote:
Ted Frater wrote:
R T Smith wrote:
"Ted Frater" wrote in message
...
| Peter W. Rowe wrote:
| On Sat, 20 Jun 2009 21:32:00 -0700, in rec.crafts.jewelry Limpy
| wrote:
|
| I know there's a way to do this, but I can't remember how.
| I have x dwt's of sterling silver.
| I want to know how much that weight of sterling will weigh in 14, 18k.
| (snip)
| What I assume you want is to know what the save VOLUME of the other
metals would
| weigh, such as if you have a casting in sterling that weighs x, how much
would
| that same model, cast in another metal, then weigh.
|
| Right?
| (snip)
|
| Heres a question for you Peter,
| whilst were on the subject of alloys.
|
| My friend John Fenn is a master silver smith. Creates miracles from
| nothing with almost no tools.
| Cleverer than me by far.
| He was asked to make a replica of the Battersea shield.
| Being the determined person he is he checked out what the original alloy
| ot tin and copper was.
| According to the analysis made by the British Museum the last time they
| did a detailed study of the shield the tin /copper ratio was between 9
| and 10 %.
| So John being the person he is he tried to purchase this alloy in
| sheet form, 1mm thick.
| It is no longer made by any Co.
| So he desided to make it himself.
| No problem getting pure tin and pure copper, neither a problem for him
| to melt and cast a suitable ingot to start with.
| However often he tried he found it would become too brittle at those
| percentages to forge out into sheet despite repeated annealing.
| By reducing the tin to 6% it worked fine.
| so he and i discussed this problem of percentages of metals.
| If the analysis by the British museum was 10% tin to copper, it had to
| be by volume ie you take for example 10 1in cubes of tin and add this to
| 90 1in cubes of copper.
| However this isnt 10 % by weight is it?
| So to get the final alloy of say 10% by analysis does one go by weight
| or does one go by volume?
| Ie do you take say 9lbsof copper and add 1ld of tin to make the 10lbs or
| 100%?
| We asked IMI who list this alloy tho dont make it anymore and they didnt
| know anyone in their Co. who had the answer when we called.
| Since John had a deadline to finish the shied, for a television
| programme, I had here some 2ft by 4ft sheets of 70 /30 copper zinc I
| sent him and he made it out of that. .
| If you want to finish up with va 10% tin to 90% copper
| So what is it? ,
|
| By weight?
| or
| By volume?
|
| ted.

The individual metal constituents in an alloy are measure by weight, not
volume.
When you have a 12k gold alloy, do you think you have equal amounts in the
volume of gold and the volume of the alloying metals?

In your story, the British Museum analysis may have come up with the 9 to
10% tin/copper ratio, but did it unequivocally say that ONLY copper and tin
were in the alloy?

Ill reply on the basis of memory which is still resonably reliable!.
From what I recall, there were minute ie less than .05% of arsenic and
lead in their analysis.
Now im still confused,because if the analysis is by percent, ie 9 to 10
parts of tin to 90 to 91% copper.
Now this has to be by volume, ie 1 part of tin to 9 parts of copper
make 100%.


You are wrong, and I pointed out why.

Arguing with you is pointless.

[[moderator's edit. sentence deleted to conform with charter restrictions.]]

So if i start with these proportions ie, 1 part of tin to 9 parts of
copper by volume, melt them together then analyse the alloy it should in
theory come out as 10 % tin to 90% copper.

Looking at it further by weight if i weigh out 1 part of tin to 9 parts
of copper, because tin is a lighter metal than copper, im going to get
more than 10 % by volume.
so when I melt and then analyse by volume its going to be more than 10 %
tin.

Getting back to my friend John he, im sure measured his alloy by weight,
it then would have been a bronze that was not suitable for forging into
sheet from the ingot.

As yet I dont see a flaw in my logic.


Why am I not surprised?!?

--
Abrasha
http://www.abrasha.com


Arguing is pointless? for its own sake? yes.
Im not trying to argue with anyone, As I said Im confused ie not clear
if you follow, how the LaTene smiths made an alloy of copper and tin,
and were able to forge out an ingot to less thn a MM over such large
areas, based on the analysis ofthe original metal.
If anyone wants to know ive the Museum guide to the shield with details
of the sizes of the parts.
If you go to google and type in Battersea Shield image youll soon see
what the object is. Its some 77cm ie 2ft 4 in in length by some 10 in wide.
john inspected the original( actually had it in the hand!!) and took
extensive measurements and photosof it before making a full size replica.
you wouldnt knowthe difference unless you examined the wood.backing.

Also I do follow everyones points about making alloys by weight,
my next step isto talk to the UK goldsmiths Co, of which im a member,who
run the Government assay offices here in the UK.
they will im sure put me right as to the question of alloys, after all
there assaying metal items all the time in their thousands.
Also so as not to leave any stone unturned ill also talk to Imperial
Metal industries at Whitton nr. Birmingham and ask them when they make
up an alloy , how do they do it? to achieve the specifications they
publish in their catalogues which ive here..
Then when ive their answers ill write it all up here.
You should all realise that I dont give up on something till im
satisfied with the answers. If i gave up on something as simple as this
what hope would there be for me as a metal craftsman on something
really difficult?

Hope you all follow.
Ted

  #15  
Old June 27th 09, 06:10 PM posted to rec.crafts.jewelry
Peter W. Rowe[_2_]
external usenet poster
 
Posts: 115
Default Math

On Sat, 27 Jun 2009 09:52:18 -0700, in rec.crafts.jewelry Ted Frater
wrote:

Im not trying to argue with anyone, As I said Im confused ie not clear
if you follow, how the LaTene smiths made an alloy of copper and tin,
and were able to forge out an ingot to less thn a MM over such large
areas, based on the analysis ofthe original metal.


And that, of course, remains an interesting question. My owh suspicion is that
those smiths were using methods that differ from our own. Perhaps tools didn't
allow as efficient working, so metal wasn't being "moved" as quickly as with
modern hammers and anvils. That more delicate sort of work might stress an
alloy less, so even a brittle alloy might respond acceptably. Or perhaps there
is some specific temperature range one could forge the alloy at wherein it
becomes more workable. Or perhaps the assumption that it's forged from an ingot
isn't entirely correct. Maybe it was initially cast as a shape that's not too
far from the current form, meaing much less forging would be required. We make
lots of assumptions as to how it was made based on how WE would do it with
modern knowledge, modern tools and equipment, and our own education. That can
lead to errors or missed methods...

I'm rather guessing that spending lots of energy wondering what the exact alloy
is, and how alloys specifications are arrived at, may be looking at the wrong
end of the question. Instead of whether the answer is in incorrect assumptions
of what the alloy is, I'd take the stated analysis as given, and get back to
the "how" of how it was worked. The sophistication of the methods of ancient
smiths is easy to underestimate. These people were absolute experts at making
the alloys they had available and used, do the things they needed it to do. And
they could take however much time was needed. No doubt the range of alloys they
could choose from was much more limited, and they may have had to make do with
whatever they could get out of the ground, or not far from it. But they'd have
compensated with the technology of how they worked it.

Back in the late 70s, as part of a school trip to england, the group I was with
was taken through the British Museum's collection, and as part of that visit,
was given a private showing of the Sutton Ho treasure. I held a couple of those
items in my (gloved) hand, and was able to use a good loupe to examine the
things very closely. Now, I didn't have the experience I have now, but I wasn't
a total beginner either, with a good deal of lapidary experience in particular
under my belt at that time. To this day, the memories of those items still
amazes me, with the precision of the workmanship. Just how those folks were
able to shape all those garnet inlays as they did, not to mention work the metal
as well as they did, given the materials and technology they had available for
the task, still amazes me. Even with modern lapidary equipment, and modern
metalworking tools, duplicating that work would be well beyond the skills of
most modern jewelers, including me, I think.

So don't discount the simple factor of the skills of the people involved. Your
answer may be as straight forward as the notion that those folks were better at
working the specific metal alloy they had, than you, I, or your friend are.

Peter


Also I do follow everyones points about making alloys by weight,
my next step isto talk to the UK goldsmiths Co, of which im a member,who
run the Government assay offices here in the UK.
they will im sure put me right as to the question of alloys, after all
there assaying metal items all the time in their thousands.
Also so as not to leave any stone unturned ill also talk to Imperial
Metal industries at Whitton nr. Birmingham and ask them when they make
up an alloy , how do they do it? to achieve the specifications they
publish in their catalogues which ive here..
Then when ive their answers ill write it all up here.
You should all realise that I dont give up on something till im
satisfied with the answers. If i gave up on something as simple as this
what hope would there be for me as a metal craftsman on something
really difficult?

 




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