Non-Chemical Pouring Smooth Bars

[samuel-a]

Just wanted to follow up on this thread:
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=61&t=11626&p=113956#p113956

It is fairly simple to achieve smooth top bars with this technique:
The pour is done while the propane flame is blazing into the mold.
Here i was casting Ag anodes and pouring them at 1100C +-. The melt was done inside a graghipe crucible heated in my "fat boy" furnace. Don't mind the color stains or frosting, my point is the smoothness of the top. My assumption is that with pure metals being casted, the surface would probably be mirror smooth.



And here are the resulting bars:
Top side.


Bottom (mold) side.


Of course, the bottom side would have looked far better if the mold it self would have been smooth and srtight.
But i think my point is pretty clear by now...

 

[kuma]

Don't mind the color stains or frosting, my point is the smoothness of the top.

Nice work Samuel!
Granted , they might not be the 'shinyest of shiny shiny's' , but these look like the sort of bars I used to dream about finding on the beach , I would gladly pay to have one of these sitting on the shelf !
Now , where did I leave those silver contacts ? Giggles :lol:
Once again , nice work and thanks for the tip!
All the best and kind regards ,
Chris

 

[samuel-a]

I would gladly pay to have one of these sitting on the shelf !

I don't know how is it on your island, but i can say for my self, it's very easy for me to source sterling silver as i'm probably the only one amongst the competition that offers to buy silver in small lots of under 500 grams (they usually bring some gold with that :mrgreen: ).

Since i'm the only one who buyes silver like that, i can buy it at low rates and the costumer is still very happy to finally get rid of it and even get somthing back.

 

[kuma]

Hi how are tricks ?
Yeah , trying to get my piece of the sterling pie was high on my list when I first set foot on this adventure , for a couple of reasons.
First and foremost , it's obviously a whole lot cheaper to obtain than karat gold , and secondly it seemed a fair bit *simpler* to process.
I have been keeping an eye out in the charity shops for the odd random piece , but with no luck so far. I think that one of the main problems I'm facing is that this island (and it's people) are litteraly driven by money. Now that there's adverts in the local paper everyday looking for scrap gold & silver , I'm guessing that it's making it harder for me to find it at local charity shops ect. as people would rather make a few bucks off of these guy's than donate to charity , which can't really be moaned at , especialy in the current climate.
I have a couple of plans though! 8)
One involves tons of what look to my amatuer eye to be fairly promising silver mine tailings (from a local mine) , and the other is antiques shops.
It's the local antiques shops (aswell as some of the jewelers) that are advertising and buying up the local scrap silver. When I was trying to shift those ormolu sconces ( http://tinyurl.com/64cc849 ) , the deal that I was trying to get for them with antique shops was a straight swap for the equivalent value in scrap sterling.
I was positive that this was a sure shot , but unfortunatly not.
Apparently the antiques shops have buyers in the U.K. who are lined up to buy their scrap gold & silver , and they have to save it for them. I believe that every now and then the buyers fly over to Jersey to pay for and pick up the scrap.
My thinking is that once I have firmly got my head around all that I need to learn (with regards to refining) , I could approach these shops and offer to refine their scrap silver (maybe even gold at some point , way way way down the road) for a fee that under-cuts their buyer's prices , then selling the refined metals , paying the shop their share and keeping my agreed cut in actual bullion.
The only concern is that I'm not too sure that I could refine for a business full time , mainly , as mentioned in a recent conversation with Harold_V , because I wouldn't want the fun and interest taken out of it.
But , who knows , I was making chemistry set's out of pen-ink and toothpaste long before I ever wanted to be a D.J. , maybe theres somthing in it , lol's :lol:
The other factor is that I'm guessing it's months inbetween them having enough to make worthwhile processing , so it might not become to much of a chore , as it were.
I could just save up and buy a shiny , stamped , off the shelf bar or two , but I see no fun in that , just a transformation of one currency into another , albeit one that I'm a whole lot less likley to spend!
We'll see , time will tell!
Many thanks for the advice , and again , nice work! 8)
With kind regards and best wishes ,
Chris

 

[lazersteve]

Sam,

Check out this thread on pouring smooth bars.

Pouring Silver Bars

We had a good discussion on what conditions affect a good silver cast. There are also a few good links to documents that may help you improve the surface of your bars. I tried a lot of different setups and there's no better mold material that I have tried for silver than graphite.

Graphite is the mold of choice for smooth finish on silver bars. Your temperature seems to be too high to me as well since silver melts well below 1100C.

Of course, there is no real need for 'pretty' bars when casting anodes, but good technique throughout your processes never hurts. Consistency is the name of the game for me so that everything becomes routine when you do it enough.

Steve

 

[samuel-a]

Cool Steve, Thanks.

I can't recall seeing this thread, it is packed with good info and recommended for every one to read.
I would probably have posted my own expiriance there had i knew about it... i don't usually miss posts...

Anyways, i think my post illustrate rather nicely what Harold recommended, the resulting bars look bad since iron mold and not pure silver was used...
But the top came out without any ripples, which was my original point.

 

[lazersteve]

Sam,

Yours turned out great for anodes. It's not too often sterling melts so clean. I've run into batches of sterling that looked horrible even after several melts. Contamination from other base metals present (other than copper) in the silver will ruin the appearance of the bars quickly.

I typically dissolve all of my cornflaked sterling (using diluted HNO3 directly or via inquarting) before it see's the cell, so my anodes are much cleaner. It's matter of preference and how often you want to have to change the electrolyte in your cell as long as your anode bars are better than 90%.

I'll merge the two topics in an effort to continue to centralize the scattered information on the forum.

Steve

 

[lazersteve]

On second thought I won't merge them as the old one was locked for some reason. I'll check out why and maybe unlock it for the merge.

Steve

 

[lazersteve]

I've had excellent results of achieving 'ripple free' silver bars simply by pouring into a five sided rectangular graphite mold with a sprue on top. The mold is simply a hollow rectangle missing one end. It gets covered with a separate piece of graphite to prevent O2 absorption as the bar cools.

The sprue is trimmed after the bar is cast and all sides are mirror like as long as the mold does not have any imperfections on it's surface, is well sooted, and is hot when the silver is cast.

Steve

 

[its-all-a-lie]

Thanks for the link Steve, i have been lookin for the name of Harolds Refining business and pictures of his bars for several months and have had no luck until now. Those are great looking bars Harold, i would love to have those put up for a rainy day. :mrgreen:

 

[Harold_V]

i have been lookin for the name of Harolds Refining business and pictures of his bars for several months and have had no luck until now. Those are great looking bars Harold, i would love to have those put up for a rainy day. :mrgreen:

You apparently found what you were looking for. My business name was Regal Refining, as you now likely know.
Yeah, the bars would have been nice to keep. Unfortunately, I do not have even one example. The vast majority of bars I cast were for customers, or were, long ago, liquidated. Don't even have the small logo stamp any longer, although I do have a pair of larger ones. I rarely used them as they required too much tonnage to make a good impression.

Harold

 

[Meh]

I ran across this video of pouring some nice silver bars today:

http://youtu.be/A0-OAXLK4UI

Never saw a torch integrated into crucible tongs before. Also shows the results of what I guess people are calling "flame polishing".

 

[Smack]

That's cool 8)

 

[samuel-a]

Thanks for the video Meh.
They are using the exact same method i have described above and do so quite professionally i might add.

It seems as if they are using a wide mouth Graphite crucible (protected a ceramic), so they need to keep the melt under flame the whole time.
Since i'm using a deep narrow graphite crucible that is covered all the time, there's no need for that.

I took some pictures from open cast of 9999 silver.
There a few things i know i need to change:
- I need a mold with a smooth finish ! The one i use is cast iron designated for Doré bullion bars which arn't supposed to look pretty.
- multiple torch tips for slower and more even cooling. I'm using now only one tip, which did not provided enough heat and did not distributed it evenly, that's why the pipes...

The one on the left was pouren under Propane flame alone, as one can see, the pipe is bigger. The one on the right was poured under propane flame slightly enriched with O2. Both pours were done at about 1000-1020 C. All in all, not bad... but could be much better. IMHO.

 

[Lou]

You can avoid the pipe by pouring into a graphite mold and pouring quickly and steadily. The faster the heat flows from the metal the less time there is for the bar to "de-stress" itself by forming contractions.

On 1000 ounce silver bars I pour, the metal will be liquid in the mold for quite some time but it doesn't pipe that badly. I preheat my cast iron mold on the exhaust port and then spray it with release.



Lou

 

[rusty]

This small 5 tr oz silver bar was poured into a vertical cavity made by inserting a piece of flat bar into a small pail of petrobond sand, the pipe ended up at the top end of the bar which is to the right hand side on the scale.

 

[samuel-a]

I preheat my cast iron mold on the exhaust port and then spray it with release.

I do too, usually i place the mold on top of the furnace cover while it heats up, this brings the mold to around 250-300 C, 5 minutes before the pour i hit it with the torch (bit O2 added) until i can see the soot starts to smoke slightly, i reckon by then the mold is at around 500C or more...

I'm under the impression that the slower the metal freezes the better finish (miror like) will turn out on top... Am i wrong about that?

 

[lazersteve]

Sam,

The mirrior finish on the top surface has a lot to do with several factors:

• How fast the bar cools.
• How evenly the bar cools.
• How much pressure is on the surface of the cooling bar (ie: from the torch)
• Purity of the silver.
• Temperature of the mold
• O2 level in the atmosphere around the cooling bar in conjunction with the purity of the silver. Pure silver loves O2 and will get 'crabby' as Harold once told me when it absorbs O2 when cooling.
• Temperature of the melt. Hotter is better to a degree as silver becomes a vapor easily.
• How even the temperature spread is on the mold. Hot and cold spots on the mold cause the bar to cool at different rates making uneven surfaces.
• Surface imperfections in the mold affect the surfaces of the bar other than the top obviously.
• Debris in or on the surface of the silver as it cools. This can be from the mold, the torch tip, slag, etc.
• Movement of the mold during the cooling process.

Steve