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#21
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granulation
On Apr 19, 10
Still, I'm curious. Can you explain how Ronda does it? thanks. Peter Rowe Hi, Peter -- I've take both of Rhonda's classes in granulation, and she teaches slightly different techniques for fine silver and for gold. For silver, no copper or other metallic salts are involved. I believe it's just finely controlled fusion. She uses a fine silver base and fine silver granules. The "glue" is a mixture of green flux, hide glue, and water. Granules are placed wet with a fine brush, the piece then dried on top of the beehive kiln until the glue carbonizes, then it is fused in the kiln with a delicate application of direct torch heat from above. It's normal for students to partially or completely melt the first couple of pieces -- I think it's her way of teaching fine control of the torch heat. Once you can consistently fuse the silver pieces, gold becomes easy. For 22 kt gold granulation, she DOES copper-plate the granules, and also brings up a 24 kt surface on the substrate by repeated heating and pickling until no oxides form. Granules are placed and fired as described above, and the copper plating disappears during firing. Regards, Bob Edwards |
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#22
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granulation
On Apr 21, 7:55 pm, Bob wrote:
On Apr 19, 10 Still, I'm curious. Can you explain how Ronda does it? thanks. Peter Rowe Hi, Peter -- I've take both of Rhonda's classes in granulation, and... Once you can consistently fuse the silver pieces, gold becomes easy... .....copper plating disappears during firing. Regards, Bob Edwards Peter, Her DVD's show the technique described by Bob above. I have tried it (not enough yet) and gotten some good results. I really like granulation and I plan to do more. Gold granulation looks so good, I hope to some day do some designs with it. I would love the saliva technique because I never run out of spit. ha Has anyone seen granulation with contrasting metals, for example gold on silver? Or Argentium on gold? Or some other contrast? -Connie |
#23
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granulation
"Peter W.. Rowe," wrote in message ... On Tue, 17 Apr 2007 22:59:52 -0700, in rec.crafts.jewelry Carl wrote: When C0nnie put fingers to keys it was 3/17/07 1:56 AM... I want to do granulation in Argentium and fine silver. I'll keep y'all posted... What little I know of granulation says you need to be using an alloy and that trying to do it with fine silver will be a problem. Do I need to know more about granulation? - C yes, you need to know a bit more. Fine silver, or fine gold, are the easiest to granulate. Alloys are increasingly difficult as their melting points drop. Granulation is done by causing the surface skin of the granules to melt before the granule itself, or the base plate, does. This is done in several ways. One is to copper plate the granules. The usual method is to put the grains in an iron cup/container, along with some well used (turned blue in color) pickle, or just plain copper sulphate solution (about the same thing, used pickle that's already at hand is of course cheaper) The resulting electrolytic action copper plates the grains, which can then be placed on the desired surface, usually with a mix of dilute orgainic glue, perhaps a trace of flux, and water. . Another method is to glue unplated grains in place on the backing surface with a mix of organic glue (hide glue, for example) often a trace of flux, and a mix of powdered copper salts. When this is heated, to glue carbonizes, and causes the copper salts to reduce to metallic copper, leaving traces of copper metal on the grains and in the contact areas. With the plated grain method, the copper is already there, so no reducing action is needed. Either way, then upon further heating, when the eutectic temperature between copper and gold or silver (whichever is being worked) is reached, the copper then forms a eutectic alloys as a liquid on the surfaces of the grains, essentially becoming a faint thin liquid layer of solder on the surface. It's so little that upon continued heating, the copper quickly diffuses further into both the grains and the substrate, leaving the grains now affixed in place. The powdered mineral Malachite ( Chrysocolla, Copper Carbonate ), has been used for centuries as the Copper bearing salt in granulation work and other fusion joinings of precious metals. The name Chrysocolla translates from the Greek to "Gold Glue". Reference to the use of the mineral as a soldering aid is found in the writings of Theophrastus ( 370 - 287 B.C.E ). In those days they didn't use hide glue, they used Camel dung and juices from "almost" dried fruits ( high fructose content ) to make the granules adhere to the intended surface and act as the supplier of additional reducing atmosphere. -- Don Thompson Stolen from Dan: "Just thinking, besides, I watched 2 dogs mating once, and that makes me an expert. " There is nothing more frightening than active ignorance. ~Goethe It is a worthy thing to fight for one's freedom; it is another sight finer to fight for another man's. ~Mark Twain ~~~~~~~~~~~~~~~~~~~~~ A further method, better suited to lower karats (not too low, but say, 18K) can be done by first heating the grains repeatedly in an oxidizing atmosphere. This causes copper oxides to form on the surface, and copper near the surface of the grains to diffuse towards the surface and concentrate there as the oxide. The layer of metal just under the surface ends up copper depleted slightly. In any case, you've got a higher percentage of copper at the surface, as oxide, than in the alloy itself. These grains are then glued in place same as for other methods, and heating lets for formed carbon (from the glue) reduce the copper skin surface to copper, and from there the process is identical. High karat alloys, or pure metals, are easier to granulate simply because the difference between the temperature where bonding takes place, and that where the substrate or granules actually melt on their own, is greater, allowing easier working without melting accidents. As to the original question, whether or not argentum silver granulates would depend on whether a copper layer on it's surface lowers the metling point at the interface between the two, and on whether the resulting eutectic bond formed if they grains can be affixed this way, is strong enough. Some alloys can be granulated, but the results are not satisfactory since the joints are so brittle the grains fall off again too easily. I don't know if this is the case with argentum, but I'd not expect it to be. fine silver, though, is relatively easy to granulate. Peter Rowe |
#24
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granulation
On Tue, 24 Apr 2007 04:53:01 +0000, C0nnie wrote:
Has anyone seen granulation with contrasting metals, for example gold on silver? Or Argentium on gold? Or some other contrast? http://tinyurl.com/yvs6td ....high caret gold onto sterling is quite easy because the silver melts at a much lower temperature. No silver "solder" such as "hard solder" is used. Still, I don't think you could call it a fusion type of operation. I surmise what is actually going on is brazing. You just coat everything with a light coat of Handy flux and use a very bushy flame over coals to get the sterling to just go shimmery. I think that if the gold granules were extremely small, the effect would show too much silver crawling up their sides. So you are trading a certain kind of refinement for color contrast. |
#26
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granulation
On Thu, 26 Apr 2007 02:00:49 +0000, Abrasha wrote:
http://tinyurl.com/yvs6td ...high caret gold onto sterling is quite easy because the silver melts at a much lower temperature. No silver "solder" such as "hard solder" is used. Still, I don't think you could call it a fusion type of operation. I surmise what is actually going on is brazing. There you go again! This is NOT brazing! A couple of definitions of what brazing is: ............. The emphasis is on FILLER metals! *Your* emphasis, not theirs. A quick and rough definition of brazing will of course tend to simplify the description of the process, demonstrating the most typical cases. If you understand brazing in depth, you find that the difference between that and welding is that in welding the metals actually mix together when both are melted at the same time. In brazing, the filler metal, by capillary action, penetrates the porosity of another piece of metal that does not melt. This is the important part, the part where the emphasis *should* be placed. The case being discussed here is not normal granulation. In the case of attaching the high caret gold to the sterling, the gold was not melted at all. The silver itself was the 'filler' metal. The fact that there was not a hunk of non-melting metal on the other side of the silver does not make it any less of a brazing operation. And it is clearly, clearly not either a fusion weld or soft soldering. The only reasonable term left is brazing. I have asked you many times to stop dispensing "knowledge" of things you know nothing or little of. I have had course work in oxy/acetylene brazing and welding, and have done considerable readings on the matter. Once again, please stop. Just as soon as you are no longer confused. Your need to 'get' me has once again made you appear silly and mean spirited. -- mbstevens http://www.mbstevens.com/ |
#27
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granulation
mbstevens wrote: I
think that if the gold granules were extremely small, the effect would show too much silver crawling up their sides. So you are trading a certain kind of refinement for color contrast. That is very interesting. I don't mind using larger granules. I used too-small granules on my last project. They are so small that the overall effect is small-scale. The design is visible but not impressive, yet the work was laborious and painstaking. The spherical and individual nature of each granule is lost when they are as tiny as I used. I will try granulation with 22 K gold on Argentium or fine silver sheet some day soon. I just need to justify the expenditure on the gold. Perhaps more fine silver practice. Peter, That is all very interesting. Perhaps some day I will use some of these materials. |
#28
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granulation
On Thu, 26 Apr 2007 02:00:49 +0000, Abrasha wrote:
The emphasis is on FILLER metals! Please stop shouting and using exclamation points. To further illustrate the error of this argument, lets consider a common use of brazing: http://www.bls.gov/oco/ocos226.htm "Brazing can also be used to apply coatings to parts to reduce wear and protect against corrosion." Sculptors often use bronze and other metals on steel and iron for decorative purposes as well, and this also is brazing. See Dona Meilach's "Direct Metal Sculpture" p. 68: "Brazing is another type of hard-soldering operation. It is used for fusing joints and for coating surfaces." |
#29
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granulation
On Thu, 26 Apr 2007 02:00:49 +0000, Abrasha wrote:
There you go again! This is NOT brazing! http://tinyurl.com/cuqzf ....metallic bond is the main way brazing holds metals together. Welding simply mixes the metals making them one chunk of metal. |
#30
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granulation
On Wed, 25 Apr 2007 22:43:40 -0700, in rec.crafts.jewelry mbstevens
wrote: On Thu, 26 Apr 2007 02:00:49 +0000, Abrasha wrote: There you go again! This is NOT brazing! http://tinyurl.com/cuqzf ...metallic bond is the main way brazing holds metals together. Welding simply mixes the metals making them one chunk of metal. Yes, though the difference between this and brazing is that the two objects/surfaces/etc being bonded are both melted. Whether they actually mix much depends on the type of welding. If both are the same type, and both surfaces melt, they will solidify as one, recrystalize as one, without needing to actually mix. If only one surface melts, as with your gold on silver granulation (according to your analysis), then this is not brazing, because you've not introduced a seperate filler alloy. Rather, the molten surface diffuses into the non molten one, producing a bond. It's the same type of bond produced by brazing, of course, but that's not really a valid label for it, since no external bonding alloy is formed, if the gold does not melt. So then, perhaps neither welding, nor brazing, is accurate. Rather, then fusing would be most accurate. However, I'd guess that when the silver melts, the gold surface in contact with it at least slightly melts too, forming a thin layer of eutectic alloy. This is then the same thing, metalurgically, as what happens with classic granulation by means the the added copper. A eutectic alloy forms at the interface, giving the bond. In normal single alloy granulation, the amount of that eutectic alloy that can form is limited by the amount of copper and the temperature to which it's raised. With gold on silver, though, because it's likely that the mix of the gold alloy, with additional silver, makes a lower melting alloy, then the potential supply of eutectic alloys is rather larger. how much forms will be limited by the temperature, and by the melting point of the resulting mix. Now, I don't know for sure that this will be what happens. It depends on whether the addition of silver to the gold alloy would raise or lower the melting point of the gold or silver. If either one is lowered, then what forms at the interface is this new alloy, and then, the proper term, just as with classic granulation, might be eutectic soldering, the term Littledale used, if I recall, to describe his method of granulation using copper or other metallic salts to do the same thing. In jewelry use, brazing is a term seldom used. More commonly used in other industries, where "soldering" refers to what jewelers call "soft solder", such as lead soldering, the term brazing in industry generally applies to the same sort of operation as we jewelers call soldering (hard soldering), and generally implies the addition of a distinct brazing alloy, not the in situ formation of one from parent metals.. In classic granulation, brazing/soldering might be an appropriate term since additional external metal, ie copper from plating or from reduced copper salts, is added to the joint resulting in a distinct third alloy that forms the joint before dissipating into the parent metal. But in the method described in this case, no external filler or solder or other metal is added. The whole is simply heated until fusion takes place. Since it happens with one or both surfaces at least slightly melted, "fusing" is likely the best term. If it were done without heating to melting temps, (as in making mokume billets), then it would be diffusion bonding. The term "fusing" is not especially specific. It does not require both surfaces to be the same, or both to actually melt. All it requires is that two surfaces or items melt together to form a bond. One can melt, or both can melt, so long as they join in the process. But in the end, might I suggest that there's way too much argument going on about the definition of the words. While words are important, much more fundamental and important is to understand the process going on. After that, the words are just tools to communicate, and in this case, even the words used are not consistant between the jewelry industry and the rest of the world. So can we just not get so worked up over which word? It's not the important part of the content, nor worth getting angry about. Peter |
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