What am I doing wrong?

[MtnMariner]

I am trying to make silver ingot from cemented silver. I did the nitric acid solution then cemented the silver out with copper. I then filtered, rinsed, and dried the silver.
I then melted it with a oxy-ace torch. Going clockwise starting with the top left: used equal portions of silver and borax/soda ash mix; used silver only; used equal parts silver and borax; used 2 parts silver, 1 part borax and 1 part borax/soda ash.
Any suggestions or comments are welcome and appreciated.

 

[Woodworker1997]

Are you saying that you mixed the borax and silver together, then melted?
If so I think that is where you went wrong. The borax needs to be melted in a hot melting dish then the silver is added and melted.

Derek

 

[Lino1406]

1. Do I see kind of green? is the silver copper free?
2. KNO3 with the borax is a must

 

[Anonymous]

Are you saying that you mixed the borax and silver together, then melted?
If so I think that is where you went wrong. The borax needs to be melted in a hot melting dish then the silver is added and melted.

Derek

If you done what Woodworker1997 is asking you, then you contaminated your silver by adding more flux/borax to the melt. Did you season your dish first with borax? If you did, then you had no reason to add any more borax into the mix.

What you need to do is get a clean melting dish, label it Ag/Silver, and use it only for melting that.

You can also try heating some diluted 10 -15 ml HCL with 200 ml distilled water for about half an hour +/- and try rubbing off the flux, if that is indeed flux. Other than that, I suggest you redissolve the silver in 50/50 nitric/water or peroxide and simply cement it with copper. After you filter and dry it enough to melt it, put it into a clean melting dish that has been already seasoned with borax. You do not need to add borax/flux when you go to melt the silver.

Kevin

 

[Geo]

the two on the left looks like stuck on flux. tap it with a hammer to break the flux. the two on the right looks contaminated, the bottom right looks like copper for sure. give them a good boil in dilute sulfuric acid. rinse with water when the solution cools.leave the bar in the solution until it cools.rinse and dry and watch for spots of oxidized metal.it could have been a metal salt on the mold.

 

[lazersteve]

Cemented silver is typically very dirty if you don't do lots of cleanup work on it before trying to melt it. Judging from the color of the slag you have a lot of contaminates in the silver still. Cemented silver tends to trap all sorts of contaminates ranging from silver nitrate to all sorts of dissolved base metals in the form of nitrates. These contaminates increase melt loss, degrade the silver purity, and make casting nice looking bars nearly impossible.

I use a standard MAPP gas torch for melting silver lots of less than 5 ounces. I prefer an electric oven for anything larger. I intentionally stay away from oxy/act because of the high temperature of the gases. Silver is easily evaporated at these high temperatures. With handheld MAPP cylinders the average temperature of the melt is lower and there is a less chance of distilling off your silver. An oven is optimal because it allows you to set the temperature of the melt. Control of the melt temperature and the atmosphere around the mold are keys to pouring pure silver into smooth shiny bars.

Silver vapors are bad for you.

Steve

 

[MtnMariner]

First, Thank you for all the comments and suggestion. Second, let me try to answer some of the questions:
* Derek - I did put the borax or soda ash mixture in the crucible first and melted it before adding the silver cement;
* Lino1406 - Yes there is green in the one's I used borax only. The silver should be copper free, I dissolved the metal in nitric acid and cemented it with copper. What would the KNO3 do for this and how much would I use?
* Kevin - Yes I seasoned the crucible with borax before attempting anything. I used the borax or soda ash mixture because I was told that the silver cement needed it to help clean it of the impurities. There are 2 crucibles I bought specifically for this and 1 is used for silver and borax only and the other for silver and soda ash mix only. When I clean the flux off the silver resembles a sponge.
* Geo - As I said to Kevin I've cleaned the flux off and all four samples look like sponges. I did have a strange thing happen that I've not been able to find an answer too in any forums or google. When I dissolved the metal in the 50/50 solution of nitric acid/water, after cooling there was about a 1/4" of crystalline structure in the bottom of the beaker. I drained and filtered the solution into another beaker before cementing the silver out. But the crystal is baffling me as to what I did wrong or how I created it???
* Steve - What is your suggestion as to clean the cement of these contaminates or purify further? I am new to this and have followed every step in the book and added a few based on the forum and comments I've been given.

 

[lazersteve]

Primary contamination in cemented silver comes from solution. Rinsing properly with hot water can eliminate most of them. Rinse/Wash until rinse liquid no longer tests positive for contaminate metals:

Copper = blue in basic ammonia hydroxide
Nickel = pink in basic DMG
Iron = blue in potassium ferrocyanide or brown in sodium hydroxide

More cation tests:

Identifying Metal Cations in Solutions

Steve