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Just need a gut check here - to reticulate a copper/silver alloy, one should first pickle the surface to etch out copper, leaving a thin skin of silver, then apply heat with a torch until the underlying copper is liquid but not flowing, allowing the harder silver skin to wrinkle up a bit without melting... Is that pretty much it?

 

I plan to pickle with distilled vinegar, and after texturing, true up the edges of my piece with files.

 

Just wanted to make sure I wasn't missing anything. Thanks.

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Chris,

 

The copper does not just "etch" out of the silver, the process is somewhat more complicated and I cannot tell from your question if you already are aware of this or not. Forgive me if that is the case! The article that Luke provided a link to is excellent and contains very useful information but, does not provide the mechanics behind the recommended surface preparations.

 

When the material (thinking silver here) is heated, the copper in the alloy reacts with oxygen and forms cupric oxide, sort of like rust except it is an oxide of copper. The cupric oxide forms on the surface, where the oxygen is, and lowers the amount of copper in the alloy in a thin layer under that of the cupric oxide. After the layer of cupric oxide, commonly called firescale, is removed, the material has a thin layer of almost pure metal on the surface. Pure metals have higher melting temperatures and so it is possible (not easy but, possible) to heat the material to the point where the alloy under the thin layer of pure metal becomes molten. When the heat is removed the differing cooling rates of the two metals cause the wrinkling.

 

The hardest parts of the whole process are getting the cupric oxide to form, removing the cupric oxide without disturbing the thin layer of pure metal underneath, and heating up the metal to the point where liquidus in the substrate is reached without burning a hole in the metal. I recommend further research on firescale, the cause of its formation and methods for removal.

 

~Bruce~

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I consider myself fairly well practiced at getting the correct heat, based on all the coin mokume I've done - the pure copper cores, and the cupro-nickel sheaths, running the copper between layers on a good sweat, all without having the piece melt out of my tongs to the floor of the forge. I'm pretty sure I can get the oxides off. The etching portion, or in your description - removing the cupric oxides - was something I thought I remembered from a Tai Goo tutorial years ago on the subject. Your description sounds right, but do you remove it chemically or mechanically? I recall Tai using the word "pickle" in between his heating cycles (which I'd forgotten until you mentioned it), and assumed he used vinegar, since that what he "pickled" his blades and everything else in.

 

The article, Luke, was fantastic. Thanks for sharing that.

 

My intent is to test with a small amount, just to validate the process, before moving on to my piece. Thank you for the input... hopefully I can pull it off.

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I'm not sure how it would play out on a larger piece, (I don't know quite what you have in mind) but I don't remember finding it too hard to get it to the right temperature and keep it there, using a jewellers' torch with natural gas and air, nor that hard to depletion gild it. I did a bit while training as a goldsmith, at a school, around 2004, and I don't think anyone there melted theirs entirely. If we all managed it, I suspect it won't give you too much trouble.

 

One thing to keep in mind is that some alloys are better for this/easier to use than others. It all depends on the alloy melting point versus the melting point of the near pure gilding layer. We used 80/20 silver copper, rather than sterling, because it gives a larger temperature difference. I seem to recall that Faberge used a similar alloy in silver.

 

It occurs to me you might be able to practice the technique in aluminum. I think the temperature difference there is rather larger, but I remember getting a similar effect while annealing some bar stock a few years ago. Molten body, solid oxide skin, waves made by torch.

 

Oh, and play around with the sort of flame (Soft and bushy, more forceful without being too focussed) to get more dramatic effects in the texture.

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I'm making Shibuichi, 25% silver, 75% copper. McCreight says it reticulates well, and on a second reading, he reccomends either Sparex or a 10% Sulphuric Acid preparation.

 

Where do you get Sulphuric acid these days?

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Chris,

 

Firescale can be a real pain in the you know what to remove. Some say that it can only be removed mechanically, i.e. abraded off. I had next to no luck with Sparex, it didn't touch the stuff at all but, I've never used the Sulfuric Acid. One place to get Sulfuric Acid, if you do not want to go through the hassle of ordering from a chemical supply house, is to get it from batteries at the junkyard. The Ganoskin article that Luke referenced mentions using a wire brush (mechanical abrasion) on the piece prior to pickling for all but the last cycle. I would follow the instructions in that article explicitly. The part about preheating whatever you set your metal upon when doing the reticulation could easily make the difference between success and failure.

 

~Bruce~

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Well, I played around with it a bit tonight. Made 25% Shibuichi, the melting went easy enough. Hammered it out flat, but not as flat as I'll hammer the final plates. Worked as advertised, a bit stiffer than copper under a hammer (cold), but worked without any signs of stress as long as it was kept well-annealed. I think I did four or five cycles of hammering/annealing before I was done.

 

I tried the depletion gilding and found I can do it with little trouble, but need to do it deeper than I did tonight for the final piece. I got a very nice silver surface after only three cycles. Because my test article was too thick, and the gilding not deep enough, I got more of a bubbled surface than a reticulated one, but from other stuff I've read in the last few days, as well as a re-read of McCreight's words on the subject, I think if I fix those two issues I'll be far more successful.

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Christopher,

 

So your physical therpist suggested some hammering? laugh.gif

 

just don't over do it man, You must be healing up pretty good ....excellent!!

 

you could try sending a PM to Dee, she has done some reticulating.... maybe she'll chime in here....haven't seen her here in a while...

 

Dick

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i have used nitric acid, sulphuric acid and sparex for a pickle and managed to get the same results in all ..

 

with no flux on the piece .. heat your silver to an annealing heat .. hold it at this temp for a few seconds and then let sit for a few seconds .. then quench int your acid pickle.

 

again - i, personally, have found that anything has worked.

 

when doing these preparation steps you need to make sure that you dont get it too hot .. as you will force the underlying metal top the surface if you do ..

 

scrub it clean ... i normally just use a hard toothbrush .. and then repeat it over and over again ..

i usually do it about 5 to 10 times .. you want it so that the oxides stop forming readily on the outside layer .. when you see that, then it should be mostly a fine silver layer outside.

 

then .. all you do is heat up the whole piece .. get it evenly heated to just a little past the annealing temp and then use your torch to focus in on points of the silver to make it reticulate ..

it will happen fast ... so you have to be careful that you dont burn a hole through the piece.

 

but thats about it really.

 

you can also place things underneath the silver to create an uneven surface so that you get more character to the piece if you want.

 

some people find that using two torches is of benefit .. as you can use one to keep the piece warm .. and the other to focus and reticulate the areas ..

i just use a jewellers torch..

 

umm ... oh and clean up with pumice powder and a toothbrush works well .. make sure that you really scrub hard, cause you will find firescale all over the place.

 

hope this helps.

this is just how i found works for me.

^_^

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So your physical therpist suggested some hammering? laugh.gif

 

just don't over do it man, You must be healing up pretty good ....excellent!!

 

 

No, but it was my little 2-pound hammer, and a 12-gram sample piece. Not what I'd call hard work. laugh.gif

Edited by Christopher Price
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i have used nitric acid, sulphuric acid and sparex for a pickle and managed to get the same results in all ..

 

with no flux on the piece .. heat your silver to an annealing heat .. hold it at this temp for a few seconds and then let sit for a few seconds .. then quench int your acid pickle.

 

again - i, personally, have found that anything has worked.

 

when doing these preparation steps you need to make sure that you dont get it too hot .. as you will force the underlying metal top the surface if you do ..

 

scrub it clean ... i normally just use a hard toothbrush .. and then repeat it over and over again ..

i usually do it about 5 to 10 times .. you want it so that the oxides stop forming readily on the outside layer .. when you see that, then it should be mostly a fine silver layer outside.

 

then .. all you do is heat up the whole piece .. get it evenly heated to just a little past the annealing temp and then use your torch to focus in on points of the silver to make it reticulate ..

it will happen fast ... so you have to be careful that you dont burn a hole through the piece.

 

but thats about it really.

 

you can also place things underneath the silver to create an uneven surface so that you get more character to the piece if you want.

 

some people find that using two torches is of benefit .. as you can use one to keep the piece warm .. and the other to focus and reticulate the areas ..

i just use a jewellers torch..

 

umm ... oh and clean up with pumice powder and a toothbrush works well .. make sure that you really scrub hard, cause you will find firescale all over the place.

 

hope this helps.

this is just how i found works for me.

happy.gif

 

 

Thank you. My good results last night were using Nitric that had been converted from Sulphuric, so I'm glad to hear you had similar success. This is an excellent description of the part nobody seems to talk much about, and I appreciate it.

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Chris,

If I'd known you needed Sparex...

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Chris, how do you convert sulfuric acid to nitric acid? Is it like with hydrochloric acid by adding potassium nitrate? By the way, if anyone is having trouble finding potassium nitrite, I managed to find it on Amazon as salt peter.

 

Doug Lester

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@Chris: ARGH! I am a bad Scale Daddy! I owe you for the batteries.

-J

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  • 2 weeks later...

Shibuichi does not really reticulate like sterling does but if done right you can get a great texturing of fine bubbles that the japanese refer to as pear skin.I once did a frog broach out of it and the texture looked just like frog skin.As for a pickle solution I use PH down from a pool supply.You get 7 lbs. for about $10.Mix it 3 to 1 water /sodium bisulfate (PH down) and heat in crock pot.

Edited by Christopher Makin
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That sounds exactly like what I got.

 

Which is funny, because McCreight says in his Complete Metalsmith, that shibuichi "reticulates easily" (p. 7, under Copper). Further reading in the section titled "reticulation" (p. 24) however, suggests that a base material of sterling or 14k is preferred, and doesn't mention the japanese alloys anywhere else as far as I can tell.

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