Producing Fine Silver Powder

[dmquigley]

This is my first post on the forum and it was suggested by Gold Silver Pro to pose my questions here; GSP has been extremely helpful to date. I am new to refining. I am trying to develop a hybrid method to cast my silver figurines. The silver I have access to has purity issues and I would like to refine it so I can produce very fine silver powder of 20 microns of less. Does anyone have a refining method or methods that will allow me to control particle size and consistently produce this very fine silver powder? Thank you.

 

[Barren Realms 007]

This is my first post on the forum and it was suggested by Gold Silver Pro to pose my questions here; GSP has been extremely helpful to date. I am new to refining. I am trying to develop a hybrid method to cast my silver figurines. The silver I have access to has purity issues and I would like to refine it so I can produce very fine silver powder of 20 microns of less. Does anyone have a refining method or methods that will allow me to control particle size and consistently produce this very fine silver powder? Thank you.

Dissolve it in nitric acid, drop it with salt and convert it to silver metal with water, sulfuric acid and a piece of steel. This should give you what you are looking for.

 

[goldsilverpro]

Here's a copy of the email I sent to dmquigley yesterday. He wants to make a metal clay mixture (of which he already has a formula for) with the powder and, evidently, the particle size is important. He wants it to be sub-20 micron. I didn't suggest using a metal, such as iron, to reduce the silver because I didn't know how iron contamination would affect the final product.

"Although I have never had the need to produce silver powder as a product, I commonly produced silver powder as an intermediate refining step. The powder was then melted into bars. In general, this involved dissolving the impure silver in nitric acid and then precipitating the silver as silver chloride (AgCl), using either hydrochloric acid or a solution of table salt (if no mercury or lead are present, this is quite selective for silver, but the AgCl must be well-rinsed to remove any traces of dissolved contaminants). The AgCl was rinsed well and then it was reduced to silver powder using a solution of sodium hydroxide (NaOH) and Karo syrup. I have no idea what the particle size of the powder was. Here are some threads on this method.
http://www.goldrefiningforum.com/phpBB3/search.php?keywords=karo&terms=all&author=goldsilverpro&sv=0&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search

Many schemes for making silver powder involve first making AgCl (as above) and then using various means to reduce this to silver powder. Most use chemicals, but a dry method for this, using heat, is in this patent. To use this method, you would need an electronic furnace with accurate temperature control.
http://www.google.com/patents?id=Mj06AAAAEBAJ&printsec=abstract&zoom=4&source=gbs_overview_r&cad=0#v=onepage&q&f=false

On the forum, 4metals outlined a method for producing the powder directly from the silver nitrate solution without going through the AgCl step. Although I haven't used it, it sounds interesting.
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=1275&p=39590&hilit=formate#p39590

Some methods are quite simple, but I think your main problem will be controlling the particle size, as it will probably be dependent on the variables, such as solution temperature. Also, different methods will likely produce different particle sizes. You could screen the powder and use what passes through, but the smallest common screen is 400 mesh, which is 37 microns. They do make smaller screen sizes, I think, but they are probably expensive and hard to work with."

 

[Noxx]

Here's a very old post of mine:

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=3264

I hope it helps...

 

[Barren Realms 007]

Here's a copy of the email I sent to dmquigley yesterday. He wants to make a metal clay mixture (of which he already has a formula for) with the powder and, evidently, the particle size is important. He wants it to be sub-20 micron. I didn't suggest using a metal, such as iron, to reduce the silver because I didn't know how iron contamination would affect the final product.

"Although I have never had the need to produce silver powder as a product, I commonly produced silver powder as an intermediate refining step. The powder was then melted into bars. In general, this involved dissolving the impure silver in nitric acid and then precipitating the silver as silver chloride (AgCl), using either hydrochloric acid or a solution of table salt (if no mercury or lead are present, this is quite selective for silver, but the AgCl must be well-rinsed to remove any traces of dissolved contaminants). The AgCl was rinsed well and then it was reduced to silver powder using a solution of sodium hydroxide (NaOH) and Karo syrup. I have no idea what the particle size of the powder was. Here are some threads on this method.
http://www.goldrefiningforum.com/phpBB3/search.php?keywords=karo&terms=all&author=goldsilverpro&sv=0&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search

Many schemes for making silver powder involve first making AgCl (as above) and then using various means to reduce this to silver powder. Most use chemicals, but a dry method for this, using heat, is in this patent. To use this method, you would need an electronic furnace with accurate temperature control.
http://www.google.com/patents?id=Mj06AAAAEBAJ&printsec=abstract&zoom=4&source=gbs_overview_r&cad=0#v=onepage&q&f=false

On the forum, 4metals outlined a method for producing the powder directly from the silver nitrate solution without going through the AgCl step. Although I haven't used it, it sounds interesting.
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=1275&p=39590&hilit=formate#p39590

Some methods are quite simple, but I think your main problem will be controlling the particle size, as it will probably be dependent on the variables, such as solution temperature. Also, different methods will likely produce different particle sizes. You could screen the powder and use what passes through, but the smallest common screen is 400 mesh, which is 37 microns. They do make smaller screen sizes, I think, but they are probably expensive and hard to work with."

That was my conern when I posted the reply as well was the iron in the mix but I know the silver can be run thru HCL or sulfuric acid to clean it out.

 

[nickvc]

When I worked for Johnson Matthey we sold filed silver and gold solder powder perhaps this might be a way to get the silver powder you want,use a new clean very fine file and try,to remove any steel coming off the file use a magnet or failing you doing it yourself ask one of the big bullion dealers for a price for your spec.

 

[goldsilverpro]

They do make woven metal screens down to 20 microns, it seems. That is probably the method used to make the 20 micron powder that is commercially available for the silver clay. If you could find a precipitation method that produced a small particle size to start with, you might get a good yield of sub-20 micron powder by running it through the screen. That's how I would first go about it since it would be the simplest way. That way, you wouldn't need stiff controls on the precipitation.
http://www.keison.co.uk/endecotts_wovenwiremeshsieves.shtml

A photo reductant might work. Maybe Manuel can chime in here.

I noticed somewhere in the literature that sterling silver clay is desirable because it has a greater strength than pure silver. Since it is an alloy, about the only way I can think of making powder from it would be to atomize it in the molten state.

 

[Palladium]

Could you not take the silver and inquart it with an excess of copper. Then separate the two with hcl ? Seems like the more copper you would add the more dispersed the silver would be as far as grain size once the copper is removed.

 

[Barren Realms 007]

I was thinking of the silver chloride method with sulfuric and steel with a stirrer that would keep the material from clumping. Either way you have to deal with a possible by product that will need to be cleaned out.

 

[goldenchild]

The silver I have access to has purity issues and I would like to refine it so I can produce very fine silver powder of 20 microns of less. Does anyone have a refining method or methods that will allow me to control particle size and consistently produce this very fine silver powder? Thank you.

I would say use lazersteve's thum cell to get your silver to .9999 and melt it into bars or just buy some fine silver. Then take a very fine sandpaper and sand down the bars or purchased ingots. Use an electric sander to speed up the process if possible. At least this way your silver wont be contaminated with other metals.

 

[qst42know]

Sand paper sheds abrasive grains.

Silver chloride reduced with lye and Karo syrup produces a fine powder doesn't it?

Where is Lou with the right way? :lol:

 

[lazersteve]

All the silver I convert from silver chloride that has not been allowed to dry out before it is converted remains as a fine powder once it dries. You can rub a pinch of it between your fingers and it will soak right into your skin leaving a gray streak.

I think this should be fine enough.

Steve

 

[Harold_V]

All the silver I convert from silver chloride that has not been allowed to dry out before it is converted remains as a fine powder once it dries. You can rub a pinch of it between your fingers and it will soak right into your skin leaving a gray streak.

I think this should be fine enough.

Steve

I was about to post the same thing. I always reduced my silver chloride with aluminum (because I had it on hand). It reduces to a sticky paste, and is so finely divided that it's difficult to handle. It was so fine that in order to melt the stuff without loss, I'd sprinkle the surface with water and tamp it tight, to a dense cover.

Harold

 

[dmquigley]

Thank you one and all for your posts - I am grateful for all of your input. Thanks again.

 

[bagus]

In general, this involved dissolving the impure silver in nitric acid and then precipitating the silver as silver chloride (AgCl), using either hydrochloric acid or a solution of table salt (if no mercury or lead are present, this is quite selective for silver, but the AgCl must be well-rinsed to remove any traces of dissolved contaminants).

I have silver nitrate solution containing dissolved mercury from silver battery batch. Can I precipitate the silver using table salt? Or should I use another kind of method?

best regards,

Bagus

 

[Juan Manuel Arcos Frank]

Sorry guys...I am late in this post because I was busy in the photo bussines.

A few years ago I was asked by a cuban friend for making silver powder that he needed it for ink conductor to metalize some kind of plastic...Well,that time silver powder made with Karo syrup process worked but I learned a little bit about silver powders,here is all the information.

I hope it helps.

Kindest regards.

Manuel

 

[Juan Manuel Arcos Frank]

David:

I have received you e mail but I did not how to aswer you becasue I did not kown your e mail adress so I will answer you by here.

The patent sounds good and easy so try to research with a little bit of silver,I have never needed such a small silver powder.

If I understood well you wanted to produce silver wildlife figurines.What kind of wildlife figurines?Are they plants,insects,flowers or small mammals?Probably you need metallization processes instead of casting processes,Exactly,what do you want to do?

Kindest Regards.

Manuel

BTW,tell me your e mail,my e mail is [email protected]

 

[Anonymous]

Sorry, I'm not certain if I should post here or start a new topic, but if one was interested in doing the same thing with Gold rather than Silver, how would one go about doing so? My interest isn't so much in recovery at this point as it is obtaining these powders cheaply, around the price of the metal. The searches I did for these powders commercially had me spending $2000 for 100 grams of gold and 250 for 100 grams of silver. I am doing a process similar to cold casting to inlay some fine woodwork, and I would much rather use Gold and Silver over brass, bronze, tin, iron, or aluminum.

 

[goldenchild]

Sorry, I'm not certain if I should post here or start a new topic, but if one was interested in doing the same thing with Gold rather than Silver, how would one go about doing so? My interest isn't so much in recovery at this point as it is obtaining these powders cheaply, around the price of the metal. The searches I did for these powders commercially had me spending $2000 for 100 grams of gold and 250 for 100 grams of silver. I am doing a process similar to cold casting to inlay some fine woodwork, and I would much rather use Gold and Silver over brass, bronze, tin, iron, or aluminum.

Where did you find 100 grams of gold for $2000? What purity?

 

[goldsilverpro]

Sorry, I'm not certain if I should post here or start a new topic, but if one was interested in doing the same thing with Gold rather than Silver, how would one go about doing so? My interest isn't so much in recovery at this point as it is obtaining these powders cheaply, around the price of the metal. The searches I did for these powders commercially had me spending $2000 for 100 grams of gold and 250 for 100 grams of silver. I am doing a process similar to cold casting to inlay some fine woodwork, and I would much rather use Gold and Silver over brass, bronze, tin, iron, or aluminum.

You must mean $2000/10 grams or $20,000/100 grams for the gold - $2000/100 g would only be about 1/2 of spot. Why not use 22-24K gold leaf? I've used it on hand-carved mahogany exterior signs for many years. $50 worth will cover about 1 to 1-1/2 sq.ft of surface area. The gold leaf lasts forever inside or outside, if you don't touch it. Neither leaf or powder will stand up to hardly any wear unless you clear coat it. Have you considered having the metals gold plated (or setting up to do it yourself)? Gold plating can be from bright to matte, light gold color to full deep color, and in many colors, similar to karat golds. If the gold plating is thick, say 2.5 microns, it will stand up to quite a bit of abuse. An ounce of 2.5 micron gold will cover about 1000 sq.in., if my math is right.