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#11
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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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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 |
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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 |
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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 |
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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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