Silver Metal Clay (PMC)

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My experience with the sodium formate was a coarse silver crystal, quick to settle. The silver chloride conversion yielded a fluffier less coarse silver.

Truth is atomization does give the particle size needed but takes the process out of the hands of most small guys, that is why I would try a reduction of silver nitrate first.
 
The sodium formate method requires some tweaking to get the particle size you want. The more concentrated the silver nitrate and sodium formate solutions, the more coarse and grainier the precipitate produced. Also, the addition rate is important.

I have much experience with both the formate and silver chloride methods. For my taste, I prefer the formate method to produce powders, but the silver chloride method works as well.
 
I have only used the formate method to drop silver from sterling and the sterling was digested at the rate of 1 gallon nitric, and 1 gallon distilled water per 100 oz of sterling. That is why my experience drops coarse silver.

Waste treatment problems with in the small shop have steered me away from the process.
 
Here is a thought, also search for information on paste solders, like bismuth and silver pastes, or how they make these solder pastes, maybe not just a search for the silver and bismuth type solder but any type of these, many of these solders you can solder with a match and paste smeared on the wire.



http://www.google.com/#hl=en&gs_nf=1&cp=25&gs_id=35&xhr=t&q=bismuth+and+silver+paste++solder&pq=bismuth+and+silver+liquid+solder&pf=p&sclient=psy-ab&rlz=1R2RNQN_enUS457&source=hp&pbx=1&oq=bismuth+and+silver+paste++solder&aq=f&aqi=&aql=&gs_sm=&gs_upl=&gs_l=&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=ebc05c09906f4efd&biw=1024&bih=587


http://www.solder-it.com/manuals/sp7msds.pdf

Another paste solder uses besides metals Diethylene Glycol Dibutyl Ether

http://www.google.com/#pq=bismuth+and+silver+paste++solder&hl=en&gs_nf=1&cp=27&gs_id=p&xhr=t&q=silver+paste++solder+patent&pf=p&sclient=psy-ab&rlz=1R2RNQN_enUS457&source=hp&pbx=1&oq=silver+paste++solder+patent&aq=f&aqi=&aql=&gs_sm=&gs_upl=&gs_l=&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=ebc05c09906f4efd&biw=1024&bih=587


Interesting solder
http://en.wikipedia.org/wiki/Solder

http://www.google.com/search?q=paste++silver+solder&btnG=Search+Patents&tbm=pts&tbo=1&hl=en#sclient=psy-ab&hl=en&tbo=1&tbm=pts&source=hp&q=paste++silver+solder&pbx=1&oq=paste++silver+solder&aq=f&aqi=&aql=&gs_sm=12&gs_upl=0l0l0l66734l0l0l0l0l0l0l0l0ll0l0&gs_l=serp.12...0l0l0l66734l0l0l0l0l0l0l0l0ll0l0&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=300ee25df671c11e&biw=1024&bih=587
 
Isn't precious metal clay still under patent protection? I was under the impression this is why it's so expensive to jewelers, as it would otherwise be easy to make. If so, even if you could duplicate it, it wouldn't be legal to sell/exchange.

That being said, my concern is primarily with the particle morphology. Atomization is ideal because the particles produced are small, dense spheres. This lends well to dispersing the powder at a high solids loading (which is important to minimize shrinkage) and directly aids the sintering (firing) process. Precipitated powders will probably not be spherical - at worst, they could be acicular (needle-like) or porous. These will not be well suited for sintering.

I have another thought though. Once when I was less experienced in melting metals, I overheated silver to the point of vaporizing it. I found later that the desk I used was covered in tiny silver spheres where the vapors had condensed and settled out of the air. It might be possible to produce a good powder in this way, if you can devise a way to collect the spheres. Maybe you could use a vacuum with a piece of filter paper?

Hope all of this is helpful
-Steve
 
As with all patents, you cannot just copy the invention. But if you can find a way to deviate from it and still make it work, then that is not covered by the patent.

For example, the PMC patent gives silver ranges of 50-90% if I remember correctly. If you could find a way to make it work with say 95% silver, then the patent would not be infringed.
 
I found this:

A new binder system consisting of cellulose acetate butyrate (CAB) and poly(ethylene glycol) (PEG) with various molecular weights was introduced. CAB and PEGs with various molecular weights had good compatibility. The blends exhibited low enough viscosity to make homogeneous feedstock for the injection molding. Shape maintenance during the extraction by an environmentally favored solvent of water was excellent, and final sintered parts had excellent dimensional stability (+/-0.3%) and high sintered density over 98%. We also found that injection cycle time was comparable to that of commonly used wax-based feedstock. (C) 2001 Kluwer Academic Publishers.
Click to expand...

Here:

http://www.mendeley.com/research/wa...hylene-glycol-blend-powder-injection-molding/

Is the post talking about the same binder that the patent is talking about? Or is this something different?

Scott
 
I think I am going to try this recipe first, I thought I would post it here for others to try as well.

Silver Powder
-particulate shape appears to work better in as spherical form, although flakes work as well. Particulate size should be less than 8 microns.
-powder is cost effective to purchase in 1kg increments (price drops to about $.60 per gram or less)

Polyolefin Powder
-this has a btu value and aids in the sintering process
-for those of you unfamiliar with this compound, this material is used in as house wraps and protective suits for printers (its also called tyvek)
-this compounds burns relatively cleanly with little or no ash

Peridur Powder
-This is basically a celluose product, it serves the same purpose as polyolefin powder
-combining Peridur and Polyolefin powder in a 1:1 ratio appears to aid the sintering process
-We suspect any simple cellulose powdered product would also work.

De-ionized Water (or double De-ionized water)
-water was be as pure as possible, otherwise the sintering process doesn't work properly due to the presense of mineral salts



Gycerin
-a 5 to 10% gycerin appears to work best, a greater concentration causes incomplete combustion (e.g. a alot of soot)
-functions as a moisture retardent
-we believe that other moisture retardents will work as well (e.g. polyethylene glycol ?) or better


Mixing

-Peridur/Polyolefin Powder must be put in the mixer first (we have a aerosol mixer for making paints but a household blender would probably work)
-Mixing the Peridur/Polyolefin Powder by itself gives it a static charge which helps adherence to the silver powder
-Add the silver powder in second
-De-ionized water/Glycerin is added next but must be atomized into the mixture (e.g. broken up into little droplets, a spray bottle would probably work) if not the mixture will clump with an inconsistent moisture content.
-90% to 95% Silver Powder/2% to 5% Peridur/Polyolefin Powder/5% to 8% Water/Glycerin
-Mixing Ratios depend on initial moisture content of silver, peridur and polyolefin powders (you will have play around with the ratios a bit).
Click to expand...

If anyone has tried this recipe, or one similar, please post your experiences.

Is there a method better than most for producing spheres of silver small enough to comply with this recipe?

Scott
 
A question for anyone who has any experience with the PMCs.

I am interested in making sterling silver and I am wondering if I can use the same recipe above for copper, then mix the correct amounts allowing for shrinkage of copper/silver clays, so that when fired, the end result could rightfully be hallmarked as sterling silver?

Scott
 
I think I'm also going to try rice starch as a binder, it seems like it would behave similar as the Japanese PMCs, and I imagine it very well might be what is used in theirs considering how widely used rice starch is, in Japan.

Anyone have experience with rice starch as a binder? :mrgreen:
 
Scott in reply to your earlier question about adding copper powder to the mix the only problem I can see is oxidisation of the copper which might cause problems with the final product, I'm also unsure how your going to get copper powder fine enough to use.
 
nickvc said:
Scott in reply to your earlier question about adding copper powder to the mix the only problem I can see is oxidisation of the copper which might cause problems with the final product, I'm also unsure how your going to get copper powder fine enough to use.
Click to expand...

Oxidation would be a problem, it could only work I think if it was made, hydrated, used immediately or made, hydrated, foil vacuum packaged for later use. I also suspect unless you are replacing with some inert gas, the clay would have a specific lifespan before it became unworkable.

I'm fascinated by the prospect, it seems it would work for other metal alloys as well, perhaps the key is in making each individual clay, and then the buyer mixing them accordingly, at the time of use.

Scott
 
NobleMetalWorks said:
nickvc said:
Scott in reply to your earlier question about adding copper powder to the mix the only problem I can see is oxidisation of the copper which might cause problems with the final product, I'm also unsure how your going to get copper powder fine enough to use.
Click to expand...

Oxidation would be a problem, it could only work I think if it was made, hydrated, used immediately or made, hydrated, foil vacuum packaged for later use. I also suspect unless you are replacing with some inert gas, the clay would have a specific lifespan before it became unworkable.

I'm fascinated by the prospect, it seems it would work for other metal alloys as well, perhaps the key is in making each individual clay, and then the buyer mixing them accordingly, at the time of use.

Scott
Click to expand...

Scott, I'm interested to know how it went out for you. Did you use that recipe you posted?
 
If I hadn't too many projects running I would try to make colloidal gold (cassius') and colloidal silver (thread about electrolysis of silver in plain water). I would try to obtain a blend of gold and silver equal to a only-gold-silver alloy for jewelry, something like 75/25. Then vaporise the water in a desiccator, if other methods of vaporizing would cause loss of PMs or use a centrifuge. When most of the water is vaporized, I would add the binder, - methyl cellulose sounds nice...wallpaper adhesive :lol:
Then I would go on vaporizing until the material has a kneadable consistency.

Just my unworthy thoughts...

edit: cassius' wouldn't work, the gold is blended with/bound to SnO2 :roll: could it be dissolved without getting the gold to coagulate?
 
edit: cassius' wouldn't work,
Click to expand...

maybe this book gives an answer, how make proper colloidal gold (Lehrbuch der anorganischen Chemie, Hollemann/Wiberg):
http://books.google.de/books?id=eGk...e&q=Lehrbuch der anorganischen Chemie&f=false

page: 1359 and 1363

I am not sure but I guess methylene chloride (cas nr. 75-09-2) is nothing for the hobbyist, probably cancerogen, unhealthy like all those nasty chlorinated hydrocarbons and capable of certain nasty reactions. On the other side it is or has been contained in common solvents. .....Au55(PPh3)12Cl6 :?: :?: :?: :lol: looks like swahili to me
 

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