Silver cement not melting! New blowtorch needed?

Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

NewBullion

Member
Joined
Jun 29, 2011
Messages
11
Hi everybody.... (Hi Dr. Nick)

I tried melting some silver cement for the 1st time (about 20g to start) with my new Bernzomatic Quickfire blowtorch and melting dish to make anodes for my silver cell. After convincing myelf, the blowtorch wasn't going to blow my hand off, I began to "melt". The powdered cement turned orange with heat but not for long. As I moved the blowtorch around to other areas of the dish, the orange areas cooled very quickly. Some seems to have turned molten (more like some just stuck together into a blob) but then cooled quickly even as it was heated and then this reddish substance appeared. I then took another dish and put in 10g of cemented silver. After 20 - 25 mins of pointing the torch at one area, realisation kicked in that no melting was happening today, I decided to stop before I ran out of propane. Tiny amount of Borax was added when molten for a matter of seconds.
Is the blowtorch just not hot enough? I was told it would be and it's supposed to reach 1500C. I was told Mapp gas cans would fit these torches.
Any advice as it should be melting at least small amounts like 10g? What is the reddish substance?
Will get an oxy/acetylene setup when Im more savvy with my melting skills. I have over 1200g of 925 to refine but practicing with 50g first.

I thank you all in advance. I'd be more worried if everything was going right for me :lol:
 

Attachments

  • BLOWTORCH.jpg
    BLOWTORCH.jpg
    297.7 KB · Views: 673
  • MELT FAIL 2.jpg
    MELT FAIL 2.jpg
    330.1 KB · Views: 673
  • MELT FAIL.jpg
    MELT FAIL.jpg
    394.4 KB · Views: 673
NewBullion :

I would guess that you have unconverted silver chloride in the mix. But you stated "I tried melting some silver cement " so that shouldn't be the case.
I'm no expert, but I have melted up a few pounds of silver buttons. I do remember a batch of silver converted from chloride (incomplete conversion) that I tried to melt, and suddenly the torch didn't seem Anyways near hot enough. It stained up my dish with some of the same grayish colors I see in your picture.That may explain some of the reddish colors your looking at also. If it smoked allot when you attempted to melt, then you most likely somehow included some chlorides in the mix.

From your picture, it don't look to me like you have enough flux in their. It is up to the flux to collect the impurities from the melt. Your dish needs a lite coating over most of the inside surface before you start the melt.

From your picture it looks like any impurities are just sticking to the surface of the molten metal and the unglazed portions of the dish.

Don't be afraid to use a little more flux, The flux also transfers the heat more evenly in the melt. It's as if the metal the dish and the flux all have to become one. Only when all three reach melt temp will you get a nice button.

If your torch can not heat a red spot about 2-3" diameter in the bottom of an empty dish then you will need a better torch, or a hotter flame. Does your torch have a really defined flame that comes to a pencil point? Those type of torches never seem to be able to heat a larger area at once, you will have to move around allot.
I use an old style naturally aspirated dual fuel Turbo torch with mapp gas, the one with the swivel neck, before they added the tick lighters. It has no problems melting a 3oz button.
Just some ideas.

Ray

PS: the definition of an Expert
The x is a sign of excellence, and the spurt is just a drip under pressure.

So I could be an expert.
 
I use a very thinly flux coated dish with no additional flux added when I melt and cast cement silver into anodes for the silver cell.

I have no clue on the red you are getting.
 
Sodbuster said:
Ray

quote]

Thanks for your help. I dissolved 925 jewellery in nitric and H20 and cemented silver out using copper. Washed the cement with tap water as was suggested in many posts. Then I dried the cement until powder form. When I held my torch in some areas, I could see the blobs appeared molten silver, but it wouldn't get fluid enough to move around. As soon as I moved the torch away from the blob, it would go back to being red hot.

Here are some pics where I added some Borax (Sodium Tetraborate) - decahydrate around the melting dish and tried to remelt the contents. A turquoise liquid appeared this time and stained the silver but again it wouldn't melt.

The torch could be better but seems hot enough to crack the clay dish. I have an electric furnace with cast iron crucible that holds 2kg of silver. I know they are disliked but would it be a bad idea to cast a large anode from cemented silver, (1kg), using an electric furnace? If I get a second cast iron crucible for my final melt (that Im told lasts 50 melts as opposed to 10-15 with the graphite), might be more cost effective??
 

Attachments

  • MELT FAIL 3.jpg
    MELT FAIL 3.jpg
    433.5 KB · Views: 635
  • MELT FAIL 4.jpg
    MELT FAIL 4.jpg
    274.1 KB · Views: 635
Also the flame coming off the silver was bright green & bright yellow (a different yellow to a standard flame).

I will solve this problem or go broke trying........
 
I agree copper in mix, as the dish cracking, you are probably thermally shocking it (changinging temperature too rapidly, it is not expanding and contracting slowly uniformly with heat changes).
 
First of all, I am no expert. Barren Realms 007, GSP, Harold and the likes can give much more insight. However, from my limited experience I can tell you two things: first, you do in fact still have some contaminates in your silver powder. Try rinsing with distilled water, or even boiled tap water, after cementation and filtering. There seems to be some copper in your powder. If your nitric is too strong, or you forget to dilute it 50/50 after dissolving your silver, it can chew up a lot of copper which can allow a few stray electrons to bind with your silver cement. You want very little free nitric during cementation. Secondly, melting silver is not as easy as it would seem. I have spent 30-35 minutes to get one ounce properly melted, sometimes having to re-melt it after pouring because it solidified during the pour. It is tricky, but practice makes it easier. I use a Bernzomatic TS with the 4 foot hose and run MAPP, and my silver will not stay molten more than 2 seconds if I remove the flame. Tricky stuff, but it looks soooo beautiful when all the hard work is done.
 
"Washed the cement with tap water as was suggested in many posts."

Did you get a white cloud (like milk) when you introduced the tap water?
Did you have allot of white/gray smoke from the melt?

If your silver wasn't completely cemented you will get some chlorides at this point.
Look for white grains in your cemented silver, use magnification if you have to.
I may be wrong but I just feel that from what I've seen in the first pictures that you have chlorides present. But pictures have lied to me before.

As others have stated, you have obvious copper ( bright green ) in the mix. that alone will change the way it melts. I think your biggest problem is inadequate heat, and improper fluxing of the dish. Like I said, If you can't maintain a red glow in the bottom of an empty dish with the torch, you will need more heat to come close to a pertly button.

Be sure and have a look at LaserSteve's website. Some good videos. One demonstrating how to properly season your melting dish.

I may be wrong but from what I understand here on the great GRF you won't want to melt values in cast iron or graphite. They make good molds, but you should not melt values directly in them.

Hope this helps
Ray
 
The solution to this problem is to use an adequate heat source. A propane torch, even one using MAPP gas, is just a dodge that is troublesome. Because silver transfers heat readily, it is rapidly radiated from the heated object. While the temperature of a propane torch is adequate to melt silver, the volume of heat required (BTU's) is woefully lacking.

If any of the readers are serious about refining and melting, an oxy/acet torch is almost mandatory. You can substitute acetylene with either natural gas or propane from a large cylinder, but you're kidding yourself if you think you can get by with a small propane torch. It simply is not up to the task, regardless of how you rationalize its use.

There is no reason in the world that you should take more than one minute to melt a troy ounce of silver. The idea that one would spend tens of minutes doing the task is more than enough evidence that you are not on the right track.

Harold
 
The torch could be better but seems hot enough to crack the clay dish.

Your dish properly preheated is unlikely to crack from being over heated. Excluding contaminants in your cement, not getting the "dish" itself hot enough may be part of your trouble. Make the dish glow or your metal will freeze where it sits.
 
Harold_V said:
Oz said:
I have no clue on the red you are getting.
I do. It's copper (oxide).

Harold
Yes Harold, I am an idiot, hindsight is 20/20. I was thinking of “cement silver” as 98%+ in silver purity. The idiot I am, I never considered there could be over 10% copper in the alloy to give even a slight red coloration to the melt.
 
Sodbuster said:
Did you get a white cloud (like milk) when you introduced the tap water?
Did you have allot of white/gray smoke from the melt?

Be sure and have a look at LaserSteve's website. Some good videos. One demonstrating how to properly season your melting dish.

Im dissolving this mess in approx 1.2ml Nitric / 1.2ml H20 per gram of silver and will cement silver out again with copper after diluting mixture.
I washed my remaining cement I thought was clean, because when washing it with H20, the water ran clear eventually. I put 200g into a filter, packed it down, poured in boiling tap water, and watched this yellow fluid drip out. Some small particles fell through into the cup, looks like cement, but it's orange. Guessing this might be copper. Amazed at how dirty my cement was (if these are contaminants) and how the orange particles have appeared.
There was no white smoke or white cloud when washing with tap water.
Thank you everybody for all your help. I hope somebody finds this useful one day. I'll keep everyone posted. I checked out LS website a few weeks ago and the vids wouldn't play for me. Can you believe I had to resort to the ancient art of reading books :shock: It's been a while.
 

Attachments

  • REWASHED CEMENT.jpg
    REWASHED CEMENT.jpg
    236.5 KB · Views: 575
  • REWASHED CEMENT 2.jpg
    REWASHED CEMENT 2.jpg
    324.3 KB · Views: 575
Too much time melting silver. Great point Harold, not just for me but for anyone spending a lot of time over the melting dish. A new torch has just went to the top of my list. One minute to melt an ounce? That would be awesome and well worth the money spent for a new torch. I'm guessing that an oxy/acetylene torch would also make it easier to pour the silver because it would stay molten a little longer?
 
juxtaposedsoul said:
Too much time melting silver. Great point Harold, not just for me but for anyone spending a lot of time over the melting dish. A new torch has just went to the top of my list. One minute to melt an ounce? That would be awesome and well worth the money spent for a new torch. I'm guessing that an oxy/acetylene torch would also make it easier to pour the silver because it would stay molten a little longer?

On my youtube channel there is a video of me melting and pouring 10 troy ounces of silver with MAPP gas. So oxy/acet will definitely do the job. There is also a video of me shooting silver using an oxy/acet rig. I chose the rig that time because the metal has to be hot enough not to freeze in the receiving crucible.
 
Oz said:
Harold_V said:
Oz said:
I have no clue on the red you are getting.
I do. It's copper (oxide).

Harold
Yes Harold, I am an idiot, hindsight is 20/20. I was thinking of “cement silver” as 98%+ in silver purity. The idiot I am, I never considered there could be over 10% copper in the alloy to give even a slight red coloration to the melt.
There need not be a high percentage of copper to yield the red coloration. Because the silver has been heated for a prolonged time, and without a flux to absorb the copper (which would then be blue instead of red), the traces of copper have oxidized, and are no longer absorbed by the silver. Fluxing, when melting silver to be cast as anodes, is actually quite important, as it is part of the purification process, removing oxides, and "lubricating" the silver so it gathers well.

Note that I recommend one NOT use soda ash as part of the flux. It tends to reverse the absorption of oxides, causing them to remain in the silver.

Harold
 
juxtaposedsoul said:
I'm guessing that an oxy/acetylene torch would also make it easier to pour the silver because it would stay molten a little longer?
A great deal depends on the flame you select, and the tip you use. Silver absorbs oxygen at a frightening rate (nine times it's volume), which it expels upon solidification. That means you should use a neutral or reducing flame, which is much cooler than an oxidizing flame. You run the fuel rich for a reducing flame, so there's no free oxygen.

The torch I used to use was a large Hoke torch. I have been unsuccessful in finding them, so they may no longer be on the market. Mine was purchased about 25 years ago. It had a large rosebud type tip, so that may serve as a guide for you. A rosebud tip is key to success, whereby you can melt large volumes of metal easily because you produce the required BTU's. If you have natural gas service, it might pay you to investigate a torch that can be so fueled. Acetylene is quite expensive, and not a necessity. Key to achieving the required heat is the use of oxygen---the fuel type is secondary. Consider using propane if you don't have natural gas.

Harold
 
Back
Top