# Ugly Brown stuff on top when I pour 14 K bars



## vincecate (Jul 12, 2010)

I am trying to make 14 K non-coins (nothing to do with any government) as pictured on http://gold.ai/
I have been buying scrap gold in a "cash for gold" way.
I have refined some gold using the Sub Zero kit from shorinternational.com and it worked!
Poured in water and got shot that looks very nice and yellow and tests nearly pure.
I melted some of this with another bar of 13 K gold to get up to 14.5 K. 

Now here is my problem, when I pour the 14 K thin bars (thin so I can put them in the rolling mill) they come out with a brown
ugly finish sometimes. Not all the bars I have poured had this problem and unfortunately I did not have a lab book!
I am now taking good notes on what I do each time, but I am not yet sure what is different when things work. 
Trying different temperatures, different crucibles, etc. Part of it may be that the other bars I poured were not 
so thin and so cooled slower. Before the lab book I tried heating the mold on an electric stove unit but think
that did not help. Maybe it needs to be covered over and not just heated from below? Or are there special
molds for pouring thing pieces to use in a rolling press?

For flux I with about 140 grams of 14 K gold I am using 1/4 tsp of Borax flux and 1/4 tsb of Boric acid.
Is this a reasonable amount?

Why do I sometimes get brown on the top? It is a very wrinkly and ugly finish. Would take a lot of filing to clean off.
I have tried soaking it in muriatic acid and that reduces the brownness some. It seems to happen right after it
is poured as if it is oxidizing then and/or wrinkling up.

I am off on an island in the Caribbean and have to figure everything out from stuff I read on the Internet.
I am pleased with what I have learned so far but I really need to be able to start make non-coins so I can 
start selling gold and get some cash coming in.

Thanks for any help,

-- Vince


----------



## Barren Realms 007 (Jul 12, 2010)

My guess would be the coloring you are having is coming from the melt not being compltely mixed and that the color is your base metals that are in your melt.


----------



## qst42know (Jul 12, 2010)

How many times have you melted this same karat gold?

It is quite normal to get worse with each melt.


----------



## vincecate (Jul 12, 2010)

qst42know said:


> How many times have you melted this same karat gold?
> 
> It is quite normal to get worse with each melt.



Yes, I have melted it several times now. I think the first melt
was scrap that came to about 13 K gold. Then second melt
I put in some pure gold to bring it above 14 K. Then trying
again and again to get a nice bar I am probably up to 5 melts now.

Why does it get worse? Anything I can do?

How much flux should I use? Do you recommend just borax flux or also boric acid? 

Thanks,
-- Vince


----------



## vincecate (Jul 12, 2010)

Barren Realms 007 said:


> My guess would be the coloring you are having is coming from the melt not being compltely mixed and that the color is your base metals that are in your melt.



What do I need to do so that it is completely mixed? Use stirring rod? Let it stay molten for some period of time?

If I am pouring 14 K gold, should I do it just above the melting point, like 1800 F or go up to 2000 F?

Thanks,

-- Vince


----------



## g_axelsson (Jul 12, 2010)

Have you any idea what the alloy contains except for the 14k of gold? Obviously the brown stuff is an oxidation product from the other 10k of base metals.

One of the ideas behind refining all gold and then alloying it again is that you know what metals you have in your alloy. If the gold that wasn't refined was produced by melting down various scrap jewelry then you probably have mixed in zinc, silver and possibly cadmium in unknown amounts. If you got some lead too in the mix then it will be very hard to roll without cracking. My advice is to refine it all and then alloying it with metals that makes it easy to work.

If you repeatedly melt your alloy then the base metals will oxidize and form slags inside the metal, creating weaker points in the alloy. You avoid that problem when refining and alloying again with pure metals.

Oh, and skip the sub zero, it is just a bunch of over priced common chemicals. A couple of hours on the forum will teach you all you need to know to start refine gold.

Good luck and welcome to the forum!

/Göran


----------



## qst42know (Jul 12, 2010)

Hot sulfuric acid or a solution of Sodium Bisulfate is used to pickle or clean the base metal oxides from the surface of karat gold castings. You still have to avoid repeated melts to keep the oxides from building up within the alloy.


----------



## Harold_V (Jul 12, 2010)

Very little attention has been given to the flame that does the melting. For melting pure gold, it's not important, but if you are melting alloyed gold, the flame is ultra critical to the outcome. 

A reducing flame will minimize oxidation of the base metals used in alloying karat gold. Should you use an oxidizing flame, the number of times that gold alloy can be melted is drastically limited. You can witness the effect simply by heating a coin known to be alloyed (90% gold, 10% copper) such as a Krugerrand. When heated to redness with an oxidizing flame, the coin surface, where exposed to the atmosphere, will turn blue. Shift the balance of the fuel in the torch so the flame becomes reducing and the blue disappears. 

You have been advised to not attempt to melt gold of unknown quality. I agree. It takes very little of the wrong element to destroy the ductility of gold, plus the endless melting causes a serious deterioration of its qualities, as you have seen. 

Assuming you choose to stay the course, there is little that is better as a pickle than dilute sulfuric acid. A light boil should remove the scale you have mentioned. Jewelers that cast gold call it fire scale. 

Regards your flux----if, when you have finished melting, your flux is not a dark black color, thick and sticky, you likely are using an adequate amount. Use more if it is as described. 

Best solution is to refine the gold first, as you've been advised. 

Harold


----------



## nickvc (Jul 13, 2010)

Im with Harold on this the only way to be sure of your alloy is to refine all the gold and start from fresh with your alloying thus eliminating any unwanted and troublesome base metals.


----------



## chemist (Jul 13, 2010)

Regarding Subzero, search the forum for Sodium Nitrate.


----------



## vincecate (Jul 13, 2010)

Harold_V said:


> Very little attention has been given to the flame that does the melting. For melting pure gold, it's not important, but if you are melting alloyed gold, the flame is ultra critical to the outcome.



I am using a gold melting furnace:
http://www.amazon.com/GOLD-MELTING-FURNACE-DIGITAL-KILO/dp/B000HWHXXI/ref=sr_1_1?ie=UTF8&s=home-garden&qid=1279026443&sr=8-1



Harold_V said:


> You have been advised to not attempt to melt gold of unknown quality. I agree. It takes very little of the wrong element to destroy the ductility of gold, plus the endless melting causes a serious deterioration of its qualities, as you have seen.



I had thought the flux was absorbing the oxidized base metal while in the furnace. Sounds like it does not get all of it though.



Harold_V said:


> Assuming you choose to stay the course, there is little that is better as a pickle than dilute sulfuric acid. A light boil should remove the scale you have mentioned. Jewelers that cast gold call it fire scale.



I can not find any sulfuric acid on this island (Anguilla in the Caribbean).
Is there any other way?



Harold_V said:


> Regards your flux----if, when you have finished melting, your flux is not a dark black color, thick and sticky, you likely are using an adequate amount. Use more if it is as described.



Thanks. Are we talking several tablespoons? Some of the stuff I read on the Internet talked of "pinches". And should I just use "Borax Flux" or is combining with "Boric Acid" better?



Harold_V said:


> Best solution is to refine the gold first, as you've been advised.



I was really hoping to save the work of doing this. Also, the way I refined my first two batches I lost the silver content.

Thanks.


----------



## vincecate (Jul 13, 2010)

qst42know said:


> Hot sulfuric acid or a solution of Sodium Bisulfate is used to pickle or clean the base metal oxides from the surface of karat gold castings. You still have to avoid repeated melts to keep the oxides from building up within the alloy.



Can't seem to find sulfuric acid on this island. Even the auto-parts stores selling battery water just have yellow water.

But a google search indicates sodium bisulfate is what is in swimming pool Ph reducer. So I can get that. So just mix some with water and soak the gold in that?


----------



## goldsilverpro (Jul 13, 2010)

I have never tried to cast 14K bars or make 14K sheet as a product. However, I've been around long enough to know that what you're trying to do is difficult. Also, I think the furnace you're using is a very poor choice. If you search the internet for 14K gold sheet, you'll find it readily available in about any thickness or temper you want. I have no idea how this sheet is made, but it could involve melting and casting in an inert atmosphere. Also, I know that you can buy 14K alloy material to add to pure gold that contains oxygen scavengers to help prevent the problems you are having.


----------



## vincecate (Jul 13, 2010)

goldsilverpro said:


> I have never tried to cast 14K bars or make 14K sheet as a product. However, I've been around long enough to know that what you're trying to do is difficult. Also, I think the furnace you're using is a very poor choice. If you search the internet for 14K gold sheet, you'll find it readily available in about any thickness or temper you want. I have no idea how this sheet is made, but it could involve melting and casting in an inert atmosphere. Also, I know that you can buy 14K alloy material to add to pure gold that contains oxygen scavengers to help prevent the problems you are having.



People were coming from the US and other islands and buying up gold really cheap here. They were flying in here, staying at hotels, and eating out at restaurants. I figured I could offer customers a higher price since I live here and did not have such overheads. So I came up with this idea of buying scrap gold and making these coins to sell to tourists. Even if it is difficult, I really want to do it at this point.  

Sending off the gold and then buy other gold is not really possible. Local shippers really don't want to ship any significant amount of gold as they feel it is too risky.

Why is the furnace I have a poor choice? What would a better choice be?


----------



## nickvc (Jul 13, 2010)

Sheet is produced by casting the gold in a furnace and then been extruded into roughly 6mm thick rough billets to be rolled to the size required.A thought has occurred to me why not cast the coins as grain this is much easier to produce especially from fine gold and the equipment needed can be had very cheaply.


----------



## shyknee (Jul 13, 2010)

vincecate said:


> qst42know said:
> 
> 
> > Hot sulfuric acid or a solution of Sodium Bisulfate is used to pickle or clean the base metal oxides from the surface of karat gold castings. You still have to avoid repeated melts to keep the oxides from building up within the alloy.
> ...



Yes, use some heat and use copper tongs to place and remove your items have some water and baking soda mix to neutralize the acid pickle.

Do this to remove fire scale and flux before you take it to the rolling mill and every time after heating to anneal ( always use reducing flame ).

When you make sheet after you pour in the mold cover with a compressed charcoal brick this will help squeeze flat the melt and create a reducing atmosphere .

I recommend you refine first to 24 k then mix casting grain to the carat you need (there are grains sold formulated for better rolling )

good luck 
shyknee


----------



## qst42know (Jul 13, 2010)

Sodium Bisulfate is a swimming pool chemical, PH down, or PH reducer.

You might consider the casting of souvenir charms or pendants rather than coins. No issues with forming sheet, cutting blanks, or coining dies.

Just a thought.


----------



## vincecate (Jul 13, 2010)

shyknee said:


> vincecate said:
> 
> 
> > qst42know said:
> ...



So I got some pH reducer which had sodium bisulfate and sodium sulfate and tried to clean it off. Used heat but did not have any copper tongs. It really did not seem to do much. After a half hour it seemed about the same. I poured the acid onto some limestone rocks and got lots of reaction, so it seems it was a reasonably strong acid.

I ended up just filing off the top of the bar to remove the ugly stuff.

The bar was about 5 mm thick. Using the rolling press I am now down to about 3.5 mm but need to get to about 1.1 mm before I can cut the circles to make my coins. Maybe done 2 hours of rolling and have 3 more to go. Never done this before and had no idea how much time it would take. There is one small crack. I am not sure what the technique is supposed to be, like should I flip it over, change ends, etc?


----------



## vincecate (Jul 13, 2010)

qst42know said:


> You might consider the casting of souvenir charms or pendants rather than coins. No issues with forming sheet, cutting blanks, or coining dies.
> Just a thought.



I have already invested in the dies, and have them here. I love the designs, so I really want to make this work somehow. The design is at http://gold.ai The 3 dolphins come from the Anguilla flag and the sailboat is a traditional Anguilla racing sailboat design.

But if I had known how much work it was ahead of time...


----------



## qst42know (Jul 13, 2010)

I have no precious metal rolling experience and I'm sure someone else will advise you but when rolling karat gold you may have to anneal this every so often to prevent the cracking as you are reducing it's thickness and a last time before you try your dies. Cold working it as in rolling will make it harder.


----------



## g_axelsson (Jul 13, 2010)

A good site to find information about working with precious metals is http://www.ganoksin.com/
I found this article on my second search: http://www.ganoksin.com/borisat/nenam/metal-rolling-n-drawing.htm

/Göran


----------



## nickvc (Jul 14, 2010)

qst42know said:


> I have no precious metal rolling experience and I'm sure someone else will advise you but when rolling karat gold you may have to anneal this every so often to prevent the cracking as you are reducing it's thickness and a last time before you try your dies. Cold working it as in rolling will make it harder.


That's spot on you need to anneal your metal and not try to reduce the thickness to fast or cracking is almost certain to occur. If your using hand rolls this is a long job and even when you get to the thickness you want you might find the sheet has blemishes which will ruin your coins especially if the alloy is suspect and sorry to sound negative but striking the coins is going to require a big press to get a decent finish and image. It would be a lot easier to cast the coins as I said before or refine the metal and use fine gold to make them as the metal is much more ductile and would be much easier to roll and blank.


----------



## vincecate (Jul 14, 2010)

nickvc said:


> That's spot on you need to anneal your metal and not try to reduce the thickness to fast or cracking is almost certain to occur.



What do I need to do to prevent oxidization during annealing?
Like coat bar with a solution of flux? Or if I am under 650 C
is oxidization not much trouble with 15 K gold? I can try the 
acid after but I am not very confident my pH reducer really
can deal with it.

Do most people use a torch or an oven for annealing?
Seems like air cooling is best for 15K gold?



nickvc said:


> If your using hand rolls this is a long job and even when you get to the thickness you want you might find the sheet has blemishes which will ruin your coins especially if the alloy is suspect and sorry to sound negative but striking the coins is going to require a big press to get a decent finish and image. It would be a lot easier to cast the coins as I said before or refine the metal and use fine gold to make them as the metal is much more ductile and would be much easier to roll and blank.



These are very small 1/10th oz non-coins (around size of a dime) and I have a 50 ton (100,000 lbs) press. Do you think this is too small for 14 K gold? Would it be ok for 24 K gold? 

On this island and the next over almost all the gold people buy is 14K gold. I can sell the non-coins cheaper if they are 14K, so I think it will be easier to find customers. I am hoping tourists will buy them and the cheaper it is the easier to get a sort of impulse buy. We have some rich tourists coming here so I think that a $100 Anguilla souvenir can sell. So I think I want to do 14K. Also, the die I have say the non-coin is 14K, so I am kind of committed to that.

Update: This article says "coat the piece with boric acid and alcohol" and quenching into "solution based on sodium bisulfate". My gold is at least 15 K. I guess this is my current plan unless someone has more advice. Oh, what kind of alcohol?
http://www.hooverandstrong.com/blog/archives/107/


----------



## lazersteve (Jul 14, 2010)

vincecate said:


> nickvc said:
> 
> 
> > ...Oh, what kind of alcohol?



Ethanol.

Steve


----------



## vincecate (Jul 14, 2010)

g_axelsson said:


> A good site to find information about working with precious metals is http://www.ganoksin.com/
> I found this article on my second search: http://www.ganoksin.com/borisat/nenam/metal-rolling-n-drawing.htm
> 
> /Göran



Thanks. That explains a lot.


----------



## vincecate (Jul 14, 2010)

lazersteve said:


> vincecate said:
> 
> 
> > nickvc said:
> ...



Thanks. My 70% Isopropyl rubbing alcohol is not good? I can probably find ethanol rubbing alcohol but have not checked stores yet.


----------



## shyknee (Jul 14, 2010)

boric acid and methanol alcohol make a paste then spread with brush before heating with torch or furnace


----------



## vincecate (Jul 14, 2010)

shyknee said:


> boric acid and methanol alcohol make a paste then spread with brush before heating with torch or furnace



If methanol alcohol and ethanol alcohol both work, would 70% Isopropyl rubbing alcohol work too? Do you let it dry or does that not matter?


----------



## shyknee (Jul 14, 2010)

does not matter the alcohol burns away instantly any way. I never tried 70%rubbing alcohol ,I would think that 30% water would boil boric off of the gold leaving spots unprotected . 
As long as oxygen(air) can not get at the metal their should be no fire scale


----------



## goldsilverpro (Jul 14, 2010)

You can buy 91% isopropyl in most grocery stores or Walmart for a dollar or so a bottle - about the same price as the 70% stuff. It burns quite well. You can also buy 99% isopropyl in drug stores but it costs $4-$5 for the same size bottle. At least, that's been my experience.


----------



## vincecate (Jul 14, 2010)

shyknee said:


> does not matter the alcohol burns away instantly any way. I never tried 70%rubbing alcohol ,I would think that 30% water would boil boric off of the gold leaving spots unprotected .
> As long as oxygen(air) can not get at the metal their should be no fire scale



Ouch. I went to 2 drug stores and 2 liquor stores (only 2 on island) and the highest percent alcohol I could get was Bicardi 151 at 75% alcohol. Now I am afraid to try this. Not many other places to try, it is a small island.


----------



## Barren Realms 007 (Jul 14, 2010)

vincecate said:


> shyknee said:
> 
> 
> > does not matter the alcohol burns away instantly any way. I never tried 70%rubbing alcohol ,I would think that 30% water would boil boric off of the gold leaving spots unprotected .
> ...



:lol: Not drinking alcohol, rubbing alcohol.


----------



## vincecate (Jul 22, 2010)

Barren Realms 007 said:


> :lol: Not drinking alcohol, rubbing alcohol.



The Bicardi 151and Boric Acid paste worked just fine. Did not get fire scale when annealing. I did 1200 F for 15 minutes, but the bar kept cracking when later rolled again. Annealed one more time and then still got more and more cracking till I gave up. Reading another place after it said 1300 F. And it may be that the bar inside was not really up to that temperature for the whole 15 minutes. Much to learn.

Someone else recommended pouring the gold into a stainless steal container such that I would get a thin layer. I tried that but it did not come out thin. The steal deformed and the gold did not flow all over. And still fire scale. Not sure what temperature I should have been at. Was at 1850 F. 

I then melted my refined gold into a small round mold and rolled this nearly pure gold. This did not have fire scale problems nor cracking problems and I never annealed it once. Pure gold seems much easier to deal with than 14K (I also wonder if a round mold reduces the cracking problem when rolling compared to rectangular). Anyway, I now have some coins but they are more than the 14K I had planned on. You can see them at http://gold.ai
I will try 14 K again sometime but probably try to understand more first.

Thanks all for your help.


----------



## Harold_V (Jul 23, 2010)

Don't know if any of this might help, but for what it's worth, here's my comments;

All of the cracking problems you are experiencing are directly related to melting old gold. It generally gets contaminated with elements that destroy gold's ductility. Don't recall if it was this thread, or another, but all of this has been discussed before. If you want to process 14K gold, which is perfectly acceptable, you're going to have to start with gold of known ancestry. Even melting solder joints can lead to problems, which eliminates a lot of gold made items. 

Annealing happens instantly----there is no need to hold gold at an annealing temperature. Get it dull red and quench in water, which, in your case, will eliminate the boric acid coating that was applied. 

If you work with pure gold, you need not worry about fire scale. If you get any, it's because the gold isn't pure. Fire scale is the result of oxidized base metals within the gold alloy. They can be the source of the cracking you have experienced, although I expect that they are just a contributor, not the sole cause. How long you hold gold molten is important. If you can't get your gold up to melting temperature readily, but must heat it endlessly, that can be troublesome. Heating with a reducing flame is the best of all worlds, but it requires a large heat source, for a reducing flame tends to be much colder than an oxidizing flame. 

Jewelers that uphold good practice do not melt old gold for re-use, and, indeed, rarely melt their gold more than once. What little gets re-melted tends to be just the sprues from previous castings, which are generally well cleaned in the pickle pot before being melted. The well pickled sprue is generally a small percentage if the gold that is melted, so it is well diluted and consumed by the new castings. By continuing this practice, gold of good quality can be assured, with no waste returned for refining. 

For the record, it was VERY common to receive sprues from my customers. If they had the slightest problem with inclusions in their castings, any remaining gold, and even, on occasion, the resulting castings were submitted for refining. Pure gold eliminates a lot of problems. 



> Someone else recommended pouring the gold into a stainless steal container such that I would get a thin layer. I tried that but it did not come out thin. The steal deformed and the gold did not flow all over. And still fire scale. Not sure what temperature I should have been at. Was at 1850 F.


Nonsense. You can NOT get gold to pour a thin layer, full stop. You should also never pour gold to a metallic surface unless it has been well treated to prevent contact (and soldering) of your gold to the surface. If you want thin gold, it must be rolled. As advised, above, start with gold alloy of proven purity and no multiple melting. 

Harold


----------

