Mike-ICFGD
Member
New member, but been lurking the forum for a while (40+ hours of reading), watched a ton of Sreetlips videos (40+ hrs) before coming here too. Man I can find 1000 diff tutorials on refining to pure, but minimal detailed info on my specific need, just to melt and homogenize a bar. It seems almost that what I'm doing is so simple noone bothered to make a tutorial or give tips on why. To this day I'm still unsure what type of torches he is using for his countertop crucible melts.
I Have no intention to refine at this stage, only melt and pour into a bar then analyze with xrf. I wish to do this to eliminate the "melt losses" that occur when sending to the refinery. (or really to keep those melt losses in my workshop for later refining vs leaving them in the refiners dustbin for them to later capitalize on. Obviously some melt losses vs theoretical gold yield will be unavoidable, Burning off grease from the jewelry, stones (which I pull all of ), underkarating at the factory, mislabeled or mis categorized gold scraps on my end, solder and platinum contaminates. But I can at least know those losses by sending in a homogenous analyzed brick and eventually retain a pin sample.
1st Goal. To be able to melt beads of karat scrap gold, pound them out with a hammer and test with XRF gun which I have available.
2nd (true) Goal. To be able to melt bars in the ~1 kilo range of karat scrap gold which are homogenous and sufficiently clean to test with XRF gun.
3rd (for bragging rights) goal: to make said bars look pretty and stamp them with my info to make them less easy to sell if they were stolen. using metal punches. which I already own. along with weights and fineness as tested by XRF gun
I have access to a iron working forge along with anvil, crucibles (already did the glazing with 20 mule team borax) and various tongs/tools for managing the items in the forge. Its one of the 2 turbojet propane burner forges as seen on amazon. I also have leather gloves and apron and intend to wear long pants and leather hiking boots as I do not have a set of steel toed boots at this time. I wear prescription glasses but any time I'm moving molten metal I put on an additional set of safety goggles. I should probably get a face mask as well.
Comparable model of the forge I'm using
https://www.amazon.com/Propane-Blac...=1695745531&sprefix=forge,aps,104&sr=8-6&th=1
I have also about 2 dozen fire bricks (the heavier ones from tractor supply not the light airy ones) which I use to create a safe work surface when dealing with pouring metals etc.
I intended to do the following in this order.
1. melt copper pipe scrap (no solder joints) into a bar by melting in a quartz crucible and then pouring into a graphite mold.
1a. I failed to melt copper using various torches I already owned by direct firing into a crucible. Propane was unable to accomplish my task with the torches I had available, a later test with Mapp gas successfully melted one copper bead appx 20 grams, but It was of insufficient to make the bead flow for pouring. I determined my torches were insufficient even when creating a small firebrick enclosure to blast the crucible in. I also tried with 2x torches
1a. I have successfully done this with minor bubbles on the receiving molded bar. I'm not concerned about bubbles so long as it doesn't create splashed metal. I melted a few buttons into a ceramic quartz crucible and have been able to get it to pouring consistency. I preheated the Graphite bar mold using the waste heat coming from the front of the forge as the crucible was inside the forge. prior to pouring I stirred with graphite rod to verify no chunks inside.
2. Repeat process above Melting directly in Graphite mold. (what specifically is the issue with melting directly in graphite? is it only that the mold will degrade over time? I know graphite crucibles are used almost exclusively with electric furnaces so I knew it could handle the temps, I verified this by doing a dry run with only a graphite mold to red hot, then a 2nd run with a small amount of copper in the mold from which I successfully made a coin shaped ingot)
Anyway, I did this with apx. 5 ozt. copper and seemed to have no ill effects. but I can see the walls of my mold seem to be getting a bit thinner. I'm comfortable that it has at least 5 more melts in it before I need to reevaluate and consider replacing. I'm now the proud owner of a copper bar with minimal bubbles on the bottom side.
3. Repeat 1 and 2 using silver. I used about 5 ozt total of silver bar scrap in the 95% plus purity range working my way up from a few grams to the full 5 ozt. Silver bars are causing issues as the bubbles are excessive the bars are ugly and I'm not super happy, however I am convinced they are homogenous. My understanding is the "boiling" that is causing the cavetation is due to oxygen being absorbed into the silver and then "fizzing" out during the cooling. some of the silver bubbling was sufficient to throw tiny beads outside the mold so this is an issue with silver I will need to address. Somehow reducing the oxygen probably by using a different tool for melting or potentially learning more about how to operate the jet burners on the forge to ensure the oxygen is completely spent on the propane before it makes it to the silver. another idea was to float some charcoal on the silver to absorb the oxygen before it gets to the silver hopefully.
4. Today's project. Since I'm now working with gold I will be using all new molds/crucibles and have marked and set aside my copper and silver crucibles already. I have samples of 22k, 21k, 23k, 24k. each between 10 to 20 grams appx. I intend to melt each into a button, hammer and test with XRF to verify my guessed karat based on xrf of the raw jewelry.
4a I then intend to mix those 4 buttons into 1 homogenous button. and repeat XRF test.
4b. I then intend to melt about 10-20 ozt of 10 and 14k karat scrap intended for refining and create a homogenous bar using the same techniques I used for the copper and silver. stir, mold, and analyze before sending to the refiner for them to do their thing and get me paid back for my investment.
Of course I will keep careful notes on the feed stock weights, and do the proper calculations of expected yield vs my measured yield of post melt weight and vs the final yield as determined by my refiner. As this is the data I'm looking for in this project and I am very comfortable doing these calculations as I have been for the past 10 years before sending loose broken jewelry to the refiner.
Once I've done the proof of concept project with my less than ideal tools available and verify I do want to pre-melt my gold in the future I will probably invest in a lower cost propane melting furnace, and a proper oxy/acetylene or oxy/propane setup as I just can't seem to get the required temps with the tools I have available.
Specific questions:
1. my understanding is the bubbling is a silver specific issue that will be much less pronounced in karat gold. am I accurate in this? If so I can worry about silver melts in the future, gold melt is what I'm concerned with at this time...
2. Other than glazing the quartz porcelain type crucibles what is the purpose of the borax flux in my situation of melting karat gold. Is it even necessary? I know when I went to a refiner and they melted in front of me they melted in tabletop electric crucible furnace not much different from the cheap ones seen on amazon, and they used what seemed like a ton of borax powder, enough that the resulting brick was coated with about 1/8 to 1/4 inch of molten slag whch was easily hammered off. Why would they do this? Is this the right thing to do?
3. I tried to be as detailed without writing 2 novels, What am I doing wrong? what is a safety concern? where might I be losing metals?
4. I have 3 types of crucibles. Small white ceramic quartz dishes, a graphite cylinder crucible about 2 inches tall by 1.5 inches wide, and a larger graphite clay crucible. I have read not to use flux with the graphite clay as it causes oxidation issues. (one of my silver melts I forgot this and added flux which seems to have damaged my crucible, I did not have time to wait for it to cool to properly observe it. Obviously these 3 crucible types have different purposes but I'm not seeing much info on this specific subject, can anyone expound? When would flux be advisable in each of these types of crucible?
5. I have been placing the crucible directly under the flame jet of the forge, is that the wrong place to do it, I suspect this is why I"m getting the oxygen contamination on silver?
For anyone who takes the time I really appreciate any information/suggestions. Thanks and God bless.
I Have no intention to refine at this stage, only melt and pour into a bar then analyze with xrf. I wish to do this to eliminate the "melt losses" that occur when sending to the refinery. (or really to keep those melt losses in my workshop for later refining vs leaving them in the refiners dustbin for them to later capitalize on. Obviously some melt losses vs theoretical gold yield will be unavoidable, Burning off grease from the jewelry, stones (which I pull all of ), underkarating at the factory, mislabeled or mis categorized gold scraps on my end, solder and platinum contaminates. But I can at least know those losses by sending in a homogenous analyzed brick and eventually retain a pin sample.
1st Goal. To be able to melt beads of karat scrap gold, pound them out with a hammer and test with XRF gun which I have available.
2nd (true) Goal. To be able to melt bars in the ~1 kilo range of karat scrap gold which are homogenous and sufficiently clean to test with XRF gun.
3rd (for bragging rights) goal: to make said bars look pretty and stamp them with my info to make them less easy to sell if they were stolen. using metal punches. which I already own. along with weights and fineness as tested by XRF gun
I have access to a iron working forge along with anvil, crucibles (already did the glazing with 20 mule team borax) and various tongs/tools for managing the items in the forge. Its one of the 2 turbojet propane burner forges as seen on amazon. I also have leather gloves and apron and intend to wear long pants and leather hiking boots as I do not have a set of steel toed boots at this time. I wear prescription glasses but any time I'm moving molten metal I put on an additional set of safety goggles. I should probably get a face mask as well.
Comparable model of the forge I'm using
https://www.amazon.com/Propane-Blac...=1695745531&sprefix=forge,aps,104&sr=8-6&th=1
I have also about 2 dozen fire bricks (the heavier ones from tractor supply not the light airy ones) which I use to create a safe work surface when dealing with pouring metals etc.
I intended to do the following in this order.
1. melt copper pipe scrap (no solder joints) into a bar by melting in a quartz crucible and then pouring into a graphite mold.
1a. I failed to melt copper using various torches I already owned by direct firing into a crucible. Propane was unable to accomplish my task with the torches I had available, a later test with Mapp gas successfully melted one copper bead appx 20 grams, but It was of insufficient to make the bead flow for pouring. I determined my torches were insufficient even when creating a small firebrick enclosure to blast the crucible in. I also tried with 2x torches
1a. I have successfully done this with minor bubbles on the receiving molded bar. I'm not concerned about bubbles so long as it doesn't create splashed metal. I melted a few buttons into a ceramic quartz crucible and have been able to get it to pouring consistency. I preheated the Graphite bar mold using the waste heat coming from the front of the forge as the crucible was inside the forge. prior to pouring I stirred with graphite rod to verify no chunks inside.
2. Repeat process above Melting directly in Graphite mold. (what specifically is the issue with melting directly in graphite? is it only that the mold will degrade over time? I know graphite crucibles are used almost exclusively with electric furnaces so I knew it could handle the temps, I verified this by doing a dry run with only a graphite mold to red hot, then a 2nd run with a small amount of copper in the mold from which I successfully made a coin shaped ingot)
Anyway, I did this with apx. 5 ozt. copper and seemed to have no ill effects. but I can see the walls of my mold seem to be getting a bit thinner. I'm comfortable that it has at least 5 more melts in it before I need to reevaluate and consider replacing. I'm now the proud owner of a copper bar with minimal bubbles on the bottom side.
3. Repeat 1 and 2 using silver. I used about 5 ozt total of silver bar scrap in the 95% plus purity range working my way up from a few grams to the full 5 ozt. Silver bars are causing issues as the bubbles are excessive the bars are ugly and I'm not super happy, however I am convinced they are homogenous. My understanding is the "boiling" that is causing the cavetation is due to oxygen being absorbed into the silver and then "fizzing" out during the cooling. some of the silver bubbling was sufficient to throw tiny beads outside the mold so this is an issue with silver I will need to address. Somehow reducing the oxygen probably by using a different tool for melting or potentially learning more about how to operate the jet burners on the forge to ensure the oxygen is completely spent on the propane before it makes it to the silver. another idea was to float some charcoal on the silver to absorb the oxygen before it gets to the silver hopefully.
4. Today's project. Since I'm now working with gold I will be using all new molds/crucibles and have marked and set aside my copper and silver crucibles already. I have samples of 22k, 21k, 23k, 24k. each between 10 to 20 grams appx. I intend to melt each into a button, hammer and test with XRF to verify my guessed karat based on xrf of the raw jewelry.
4a I then intend to mix those 4 buttons into 1 homogenous button. and repeat XRF test.
4b. I then intend to melt about 10-20 ozt of 10 and 14k karat scrap intended for refining and create a homogenous bar using the same techniques I used for the copper and silver. stir, mold, and analyze before sending to the refiner for them to do their thing and get me paid back for my investment.
Of course I will keep careful notes on the feed stock weights, and do the proper calculations of expected yield vs my measured yield of post melt weight and vs the final yield as determined by my refiner. As this is the data I'm looking for in this project and I am very comfortable doing these calculations as I have been for the past 10 years before sending loose broken jewelry to the refiner.
Once I've done the proof of concept project with my less than ideal tools available and verify I do want to pre-melt my gold in the future I will probably invest in a lower cost propane melting furnace, and a proper oxy/acetylene or oxy/propane setup as I just can't seem to get the required temps with the tools I have available.
Specific questions:
1. my understanding is the bubbling is a silver specific issue that will be much less pronounced in karat gold. am I accurate in this? If so I can worry about silver melts in the future, gold melt is what I'm concerned with at this time...
2. Other than glazing the quartz porcelain type crucibles what is the purpose of the borax flux in my situation of melting karat gold. Is it even necessary? I know when I went to a refiner and they melted in front of me they melted in tabletop electric crucible furnace not much different from the cheap ones seen on amazon, and they used what seemed like a ton of borax powder, enough that the resulting brick was coated with about 1/8 to 1/4 inch of molten slag whch was easily hammered off. Why would they do this? Is this the right thing to do?
3. I tried to be as detailed without writing 2 novels, What am I doing wrong? what is a safety concern? where might I be losing metals?
4. I have 3 types of crucibles. Small white ceramic quartz dishes, a graphite cylinder crucible about 2 inches tall by 1.5 inches wide, and a larger graphite clay crucible. I have read not to use flux with the graphite clay as it causes oxidation issues. (one of my silver melts I forgot this and added flux which seems to have damaged my crucible, I did not have time to wait for it to cool to properly observe it. Obviously these 3 crucible types have different purposes but I'm not seeing much info on this specific subject, can anyone expound? When would flux be advisable in each of these types of crucible?
5. I have been placing the crucible directly under the flame jet of the forge, is that the wrong place to do it, I suspect this is why I"m getting the oxygen contamination on silver?
For anyone who takes the time I really appreciate any information/suggestions. Thanks and God bless.
and since I'm dealing with molten metals and reasonably intimidated by the process and inherent dangers I just posted exactly what my plan was/what I wanted to do and asked for help/tips as was explained in many many posts 
