Shibuichi

[GinZaikuShi]

For the last week, I've been playing around with making Shibuichi.  I've done a few different combinations, from melting down old war nickels to weighing out a few silver dimes and melting them down in scrap copper.

 

I have a few questions to improve my casts.

 

- Would the use of bronze, as opposed to a more pure copper, taint my alloy?

 

- I've seen some vidoes of people making Shibuichi, casting into boiling water.  What is the reason for this?  I've been casting in open air onto a brick of rammed earth.

 

- I've heard not to use Muriatic acid when pickling silver, but that it's good to use on Copper.  How does it do with a mixture?  Should I use sulphuric instead?

 

- Although it looks like most of it was left in the crucible after casting, I believe some of my Shibuichi has a bit of manganese in them (from the war nickels).  Any idea how this might effect patination and working of the alloy?

 

Thanks

 

ML

 

[Chinobi]

Haha, wow you have been busy! Kudos for experimenting :)

For starters, shibuichi is fine silver and straight copper, different compositions for different 'qualities' or grades of shibuichi. So I dunno what you would call the nickel alloy or bronze for that matter, but you might be on your own there :) (unless you do the math on the composition and and it comes up as a known mix) remember also that coin grade silver is 90/10 silver/copper IIRC, so factor that 10% copper into your final composition. I don't think bronze would 'taint' it persay, it just wouldn't be what you think it is and it might not behave as you expect said alloy to perform.

The water casting method is a way of casting reactive alloys (copper heavy) into an environment with less free oxygen circulating around it to form oxides. There is less oxide development, which means less imperfections in the ingot, and less losses trying to get rid of them. Been a while since I looked into it but I don't think the water needs to be boiling, it just gets there in a hurry after you pour! The molten metal vaporizes the water on contact and creates a shield of water vapor on the way down and actually a bubble when it puddles at the bottom. So you end up with a puddle of liquid metal shielded by a gas bubble in a pot of water, which is pretty awesome when you think about it :) when the metal looses enough energy it can no longer vaporize the water as aggressively and the bubble collapses and finally quenches the ingot. From there you can start to clean up the edges and form the ingot into your sheet stock or whatever you need.
Check out Ferguson's book, he has some info on the process, and there are several YouTube bids on the subject as well.

I haven't heard anything relating to silver and muriatic (hydrochloric) acid, I use Skaylex which lists sodium bisulfate on the label and that it is a 'safer alternative to sulfuric'. Sulfuric and nitric are listed as pickle acids as well, but I don't want anything that nasty kicking around my house :)
Doubt the link will take but this was an article a quick google turned up
http://jewelrymaking.about.com/od/solderinginformation/a/032806.htm
Take a look around the Internet and the alchemy section, I'm sure pickle recipes and procurement have been beaten to death here. Check jewelry supply websites for availability or web amazon.

I don't know what the effect of manganese on a copper alloy would be, but I would probably treat it as a contaminant for a project like this. I believe it makes steel tough like nobody's business (google Mangalloy, German guy invented it I don't remember how long, but it's the stuff they made military helmets in WWII out of) so I could guess that it would make working a Mokume piece *real* unpleasant. Also, if you suspect that it has precipitated out into your crucible you should treat that crucible as contaminated and not use it for or subsequent pour. General rule if you want to really keep your alloys pure and traceable (so you an market them legally) is one crucible per alloy or metal.

Shibuichi alloy grades vary considerably but first quality is listed as 60% fine silver to 40% pure copper, and can go down to 'contemporary' grade at 5% fine silver to 95% pure copper [Kidwell technical papers]

LOVE to see some pics of what you have been up to! Keep at it!

[GinZaikuShi]

Here is my first piece of Shibuichi.  It's a 25/75 mix of silver and bronze.  I did accound for the ten percent copper of the coins.  It's been forged down to about a .5 mm sheet and reduction gilded in a acid solution that I made.  the acid does some interesting things, first it eats away at all the surface copper and the piece looks like sterling, then the surface turns a beautiful bright white.  Hard to see in this picture, but this piece is white, pickled for a few hours.  The back side was sanded down, so it's still got that goldist/copperish Shibuichi color.

 

 

I've started working with my piece that had manganese in it.  I've noticed some interesting things.  It retains a grey color when sanded, darker than silver but with that silver luster.  It doesn't seem to need to be annealed as much as straight shibuichi, and anneals well at a blue/purple temper color.  Any more than that and it seems to get crumbly.  It works different than copper or silver, more like nickel, very stiff. '

 

[GinZaikuShi]

More and more questions....

 

I put two large pennies in my pickle to give it some copper content (Copper II Chloride).  I just pulled them out and washed them off and saw something pretty cool.  One penny is still copper colored, the other is a deep, matte black.

 

From what I can find on the internet, as far as the metal content of these pennies, is that the black one has 1% more tin than the other.  Besides that, they seem to be indentical.  If anyone has a good knowledge of chemistry and can help me figure out how to repeat this, please speak up.  Black copper and white Shibuichi would make a wonderful contrast on a knife handle.

 

I will try and get a picture up tonight.  This black finish appears to be more "black" than a Liver of Sulpher "black-brown" finish.

[Chinobi]

Interesting results indeed :) really hard to say what's going on with the mystery recycled metal alloys because it's real hard to say what they are and how they will behave (at least I have no clue). The depletion guilding will also alter how the metal performs when bonding.

I dunno what's up with the black patina but maybe try using that vintage of coin in your stack.

[GinZaikuShi]

Black penny.

 

 

Will probably flatten it out into sheet and use it for a knife handle.

 

[Chinobi]

That would look pretty cool :) does it seem like a tough patina or just a dusty coating that you can rub off?

[GinZaikuShi]

It's on there pretty well.  Couldn't rub it off, cleaned it with alcohol.  It feels like a powder coat.

[Steve Sells]

remember that for a patterned billet to bring out the contrast, I see so many mokume that people just dont take the time to finish.