Silver Metal Clay (PMC)

There is a growing market out there for silver (gold too) metal clay. It is made from pure silver power which is very small in size (atomized) and an organic binder. it can be modeled like clay, dried, and fired to make jewelry or whatever.

Does anyone have any idea what the organic binder used to make the clay is?

Usually a mineral oil.

I know that the gold and silver inks used in the heyday of thick film hybrid manufacturing for silk screening circuits was just metal powder and pine oil. I didn't think it would be that simple.

I think I'll try and do it with pine oil for starters.

They use rosemary oil and other aromatic heavy oils for the paint on gold and platinum that Degussa used to make.

hmmmm - one common thing to PMC I've seen is that it's wet - you have to dry it before firing. I wouldn't wet too well if it were an oil?

I've heard it's something like methyl cellulose, which can be wet. The air drying takes care of the water and the firing takes care of the binder.

Maybe a product MSDS will reveal a secret.
Or patent search.
I have also read old books of facts and formulas that had similar recipes of how they used to make things.

I got the methyl cellulose fact from a patent but it was vague in percentages and specifics. I don't blame them they get quite a premium for this stuff so they keep the formula secret.

It is really neat stuff, you mold it like modeling clay, plan ahead for the shrinkage, and dry it and fire it and you have a piece of jewelry. I'm sure there's more to it than that but it seems to be a valuable asset to a manufacturing jeweler. And a good way to get a premium on your silver.

I know that a company called Rio Grande Jewelers Supply markets the stuff. I will see if I can get any information on the composition, but it is likely a trade secret and not available to the general public.

My aunt started working with this a couple months ago. She's made a lot of flat pieces with designs on one side. From what I can tell, it doesn't work too well for 3D sculptures. or can it?

where do they get silver powder? cemented from copper? ^_^

Westerngs said:

I know that a company called Rio Grande Jewelers Supply markets the stuff. I will see if I can get any information on the composition, but it is likely a trade secret and not available to the general public.

Click to expand...

You could send a sample in to your state lab for analysis.

Conductive ink may be another product you could make with silver;

http://hackaday.com/2012/02/24/diy-conductive-ink-lets-you-freehand-circuits-on-the-cheap/

http://jordanbunker.com/archives/41

Jim

4metals - I also looked for the binder awhile back and I'm thinking I found some patents. Maybe I kept a file - I'll look and also check my bookmarks.

Patent for PMC

There is disclosed a precious metal article which is formed of a solid-phase sintered product of a precious metal powder. For manufacturing the precious metal article, a moldable mixture which contains a precious metal powder and a binder removable by sintering is shaped into a prescribed molded object, and the molded object is then subjected to sintering. The moldable mixture is produced by preparing a precious metal powder, preparing a jellylike cellulose binder by blending a cellulose with water and leaving for a prescribed period of time, and blending the precious metal powder and the jellylike cellulose binder together. The most preferable moldable mixture contains 50 to 90% by weight of precious metal powder, 0.8 to 8% by weight of water-soluble cellulose binder, 0.08 to 3% by weight of a surface-active agent. 0.1 to 3% by weight of oil, balance water and unavoidable impurities. The precious metal powder preferably contains gold powder and powder of an alloy containing silver or copper, and the gold powder is obtained by submerged-reduction method.

a) Precious metal powder:

Powders of precious metal such as gold, silver, copper, platinum and their alloys are main constituents for the moldable material to be obtained. If the content is less than 50% by weight, desired effects cannot be obtained. On the other hand, if the content exceeds 90% by weight, the resulting moldable material is inferior in extensibility and strength. Therefore, the content of the precious metal powder has been determined so as to range from 50 to 90% by weight.

In addition, if the average particle size of the precious metal powder exceeds 200 μm, the extensibility and strength are deteriorated. Therefore, it is preferable that the average particle size of the precious metal powder is no greater than 200 μm.

(b) Water-soluble cellulose binder:

When heated, the water soluble binder is quickly gelled, so that it is very easy to keep the shape of the molded article. However, if the binder content is less than 0.8% by weight, such an advantage cannot be obtained. On the other hand, if the content exceeds 8% by weight, fluidity is unduly increased, so that it becomes difficult to mold the mixture. Therefore, the content of the cellulose binder is determined so as to range from 0.8 to 8% by weight.

In the foregoing, methyl cellulose and/or ethyl cellulose are favorably used as the water-soluble binder of the above kind.

(c) Surface-active agent:

A surface-active agent breaks solid substances which are formed by the reaction of the binder with water, and facilitates an efficient mixing of the precious metal powder with the binder. However, if its content is less than 0.03% by weight, desired effects cannot be obtained. On the other hand, if the content exceeds 3% by weight, the fluidity of the moldable mixture is unduly reduced, so that molding operation cannot be smoothly carried out. Accordingly, the content of the surface-active agent to be added is determined so as to range from 0.03 to 3% by weight. As described above, polysoap or alkyl benzene sodium sulfonate is preferable as this agent.

(d) Adhesion-preventing agent:

When a small amount of adhesion-preventing agent, or oil and fat, is added, the moldable mixture is prevented from sticking to hand during the molding operation. However, if the content is less than 0.1% by weight, the effects cannot be obtained. On the other hand, if the content exceeds 3% by weight, the moldable mixture becomes oily and slippery, resulting in poor handling characteristics. Therefore, the content of the adhesion-preventing agent is determined so as to range from 0.1 to 3% by weight.

This agent may include higher organic acid such as phthalic acid, higher organic ester such as di-n-octyl phthalate or di-n-butyl phthalate, higher alcohol, higher polyhydric alcohol such as polyvinyl alcohol, polyethylene glycol, and higher ether.

Furthermore, it has been found that when ethylene glycol is added in an amount of no greater than 30% by weight, preferably 2 to 10% by weight, with respect to water, the moldability of the resulting mixture can be further improved. However, if the content exceeds 30% by weight, the viscosity is reduced, so that the moldability deteriorates instead.

Patent #5328775

Found it here:http://bbs.homeshopmachinist.net/showthread.php?t=41842

I did keep a patent file. Here's the numbers. The last 3 are patent applications. Some are more applicable than others.
5328775
5702501
6383248
6572670
7081149
7387762
20050241438
20070000351
20110064937

Search for the numbers here:
http://www.google.com/ptshp?hl=&sourceid=navclient-ff

This thread is a great example of refiners helping refiners.

This forum is truly unique.

Thanks for all the input.

Could someone maybe put a bit of this silver clay into a solvent that dissolves the organic materials, filter out the silver powder and determine the particle size and shape under a microscope? I wonder how they make this silver powder, and I think that a big part of the secret behind making this clay lies in the preparation of the powder. A powder that sinters to form a massive silver artifact far below the melting point has to very fine I would think.
I think of the possible applications for making silver labware from this clay. I have a little silver crucible and it is great for doing caustic alkali melts.

The silver is melted and poured with high pressure water jets fired at it, I think it was 4metals that posted about it so he has no problems with the silver it's the binder that's unknown.

The secret may be behind the production of the powder but I would also try dissolving some fine silver and filtering it and dropping it as a chloride and reducing it with Karo. This makes a fine clay like mud and with the right binder it may be just a question of adding the binder to your reduced chlorides.

My interest in this material is that it would be a good and easy way if reduced chlorides could produce a workable product, for our members to get an added value on their silver to sell to local jewelers.

You might get better powder if you precipitate it with sodium formate. The drawback here is that not all the silver gets precipitated out unless you use a huge excess of reagent.

The powder produced however can range from the 10 micron to the 500 micron range. You just tweak the process a little to make the size you need.