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SMELTING ORES

HOW TO SMELT ORE CONCENTRATES

 “SEASONING” THE KILN & CRUCIBLE PRIOR TO USE

Place the stacked kiln, containing an empty crucible, into the microwave and set the timer for 15 minutes on high. At the end of the 15 minute cycle, remove the kiln from the microwave and allow the kiln and crucible to cool to ambient temperature. Repeat the process again, setting the timer for 15 minutes. This process will drive off any moisture absorbed by the kiln, kiln shelf and/or the crucible from the atmosphere. New crucibles should also be “seasoned” using the above method for 15 minutes before use as well. Moisture absorbed from the atmosphere can cause the crucibles and or kiln shelf to crack or break during the firing process if not “seasoned” properly prior to use. It’s a good practice to repeat the “seasoning” process after extended periods of non-use of the kiln prior to firing. You’ve got a lot of time and effort invested in your black sands concentrates, so don’t get in a hurry and skip this “seasoning” process.

 

 

CHARGING THE CRUCIBLE

Place 3 parts flux to 1 part of your dry black sand concentrates into a quart jar. Place the lid on the jar and roll the jar until the materials are thoroughly mixed and homogenous. Pour the mixture into the crucible, leaving an inch space from the top of the crucible. Never pack a crucible with the mixture or use wet or damp black sand concentrate, as the material can rapidly expand upon heating and can crack the crucible or spill over the top. Lesser amounts of the black sands and flux mixture will work just as well as filling the whole crucible. If, in your experience after firing, the flux is thick and viscous and doesn’t want to pour readily using the 3 to 1 mixture, you can increase the mixture to 4 parts flux to 1 part black sand concentrate or 5 to 1 and it will thin out the flux and make pouring easier. Your experience will ultimately determine the best ratios for your concentrates. Remember, the more fine gold contained in your black sands concentrates, the bigger the button will be and the better the process works. Keep the nuggets and pickers out of your black sand concentrates and smelt the rest - this is my policy.

 





 FIRING THE KILN

Place the charged crucible on top of the kiln shelf in the center of the shelf. Stack the hollow kiln squares around the crucible, centering them around it so that the crucible does not touch the kiln and there is approximately 1 inch of clearance between the lid and the top of the crucible. Place the 1” thick solid kiln square lid on the top of the kiln. Carefully set the kiln inside the microwave, centering it in the microwave. Close the microwave door tightly and gently - do not slam. Set the microwave power level on high and the timer for 45 minutes and start the microwave. During the microwaving process DO NOT peer into the microwaves’ window to see what’s going on inside the microwave. Temperatures inside the kiln are going to reach in excess of 2300 degrees Fahrenheit and you don’t want your face in front of the glass door if the crucible fractures, boils over, or the kiln shelf cracks. Give this process of microwave smelting the respect it deserves and BE SAFE this process is not a toy.

After 60 minutes, open the microwave door and, wearing heat proof gloves, safety glasses and apron, carefully lift the entire kiln out, holding it by the base. Hold the kiln with both hands when moving from microwave to heat-resistant surface. The kiln shelf will be very hot, so be sure to use caution here. Place the hot kiln on a heat-resistant surface. A 12” x 12” clay tile will work well. Carefully lift the lid to check the color of the crucible and contents. They should be glowing yellow-orange. If they are not, replace the lid and return the kiln and contents to the microwave and continue microwaving for an additional 10 minutes. Typical microwaving times are from 45 to 60 minutes, depending upon the microwave you are using. Again, remove the hot kiln and place on a heat-proof surface. Lift the lid again carefully. Assuming that the crucible and contents are glowing yellow-orange by now, completely remove the lid with one or two layers of the kiln and place on another 12” x 12” tile or heat proof surface. This allows for access to the heated crucible. Grasp the crucible with the tongs and pour the contents of the crucible into the conical mold. 

 

  

USE EXTREME CAUTION when pouring the molten material from the crucible into the cast iron mold. The mold and tongs must be preheated in an oven or on top of a stove burner to prevent the molten glass and metal from splattering and erupting like a miniature volcano. The best way to pour into the molds is to pour a very small amount first, wait a half second, then pour the rest of the material into the mold. Remember to Pre-heat your mold and tongs and drive off any moisture before pouring our crucible contents into the moldTrust me; you don’t want liquid 2300 degree metal and glass splattering all over you or anything near you.

 

POURING MOLD

I place a conical mold on a 16”x16”x1” clay type “paver stone” used for walkways prior to pouring the molten material into the mold. This provides a good fireproof surface for the mold to sit on and a place to set the hot crucible onto after you have poured the molten material into the mold. This is also a good fireproof surface, should you happen to spill any of the molten material during the pouring process, or overflow the mold itself with the molten flux. Remember that the 2300 degree plus liquid, if spilled onto a wooden bench, will immediately result in the bench bursting into flames, as will the crucible after pouring, if set upon any unprotected surface. At least have the fire department’s number handy if you choose to skip this advice.

 

         

 

BUTTONS

After pouring the molten mixture into the conical mold, the cooling process begins. The molten flux is actually a form of borosilicate glass and, during the cooling process, the glass will shrink and crack. Often times during the cooling period, small shards of glass will fly outward from the cooling mass in the mold with high velocity, as well as from the small amount of flux coating the inside of the crucible. These flying pieces of glass obviously present a hazard when within range of them. Always wear safety goggles and your protective clothing while in the immediate area of the cooling mold and crucible. After the mold and the borosilicate glass have cooled, invert the mold and the conical shaped glass will drop out of the mold. The smelted metal “button” will be on top of the conical shaped glass.  In my experience, the glass splinters shooting from the “button” and glass can occur at any time until the metal “button” is completely free of the glass. So, it’s also a good idea to wait on taking family pictures until after the cooling process is complete. In other words; keep everyone, pets included, out of your play area. I hold the metal “button” in my gloved hand and tap the glass on the button with a suitable tool to remove the glass from the button. Once again; always wear your goggles and protective clothing when working with the glass and metal 'buttons' until the buttons are free of the glass. 

After I have cleaned the “button” and am finished with the glass, I like to break up the glass and inspect it carefully for any small metallic beads or slivers of metal that didn’t pour out of the melt. In my experience, if you are following the directions given here, there should be very little, if any remaining metal beads in the flux. However, stuff happens and if something was not quite right, or the flux was thick and viscous during the pour, ultimately nothing need be lost. I’ll save that glass and when I get enough of it, I’ll crush it to minus 10 mesh, using a mortar and pestle. I’ll then pan the glass down to a concentrate, then dry it, charge a crucible with the glass concentrates and a 1 oz. shot glass of flux, fire the mixture in the kiln and viola, problem solved.

 

      

FREE MILLING GOLD & SILVER ORES

Yes, I know they’re rare and that a lot of the ore can be worth several times spot price, as specimen material. However; I have found gold and silver ores in old abandoned mines and mine dumps that were nothing much to look at, that were very high grade. For instance, I know of an old mine in Nevada that select ore samples assay from 350 to 500 ounces per ton in silver that are nothing much to look at. I’ve also run across gold ores that assayed over 2 ounced of gold per ton that you can’t see the gold in as well. Basically you can treat these free milling ores the same as the black sand concentrates and recover the metals from them. Obviously the ore needs to be finely crushed and panned down to a concentrate before firing them in the microwave kiln. The ores need to be “free milling” and in an oxidized state for the best results.

I start with a 1 part dry ore concentrates and add 4 parts of the flux mixture, to charge the crucible.  The ore concentrates can contain more impurities than the black sand concentrates and can be more difficult to work with, however, with experimentation, they can be smelted. There are different mixtures of fluxes that can be used, as well as processes that can be used for high grade sulfide ores. 


IMPORTANT SAFEGUARDS

  • Set up your workspace away from your home, in a well ventilated area, such as the garage with the door open, or outside.
  • Keep your workspace free of flammable materials.
  • Do not use the microwave kiln in the house. The temperatures achieved during the process are in excess of 2300 degrees Fahrenheit and the danger of fire is too much of a risk. Also: there are fumes coming off of the crucible during the smelting process that can be hazardous if not properly ventilated.
  • A separate, dedicated 1200 watt microwave is recommended. Do not use your household microwave for smelting and expect your coffee to taste good after you warm it up. Using a microwave with less than 1200 wattage is not recommended, as smelting times would take much longer.
  • Allow at least 1 inch space between the top of the kiln and the ceiling of the inside of your microwave oven.
  • Allow the microwave to cool at least 20 minutes between firings.
  • Keep microwave door open between multiple firings, for effective cooling. Always remove the kiln from the microwave after firing, to prevent heat from building up in the microwave and damaging it.
  • Do not try to heat a crucible in the microwave alone, without Ceramic Fiber Kiln in place around it.
  • Do not leave microwave unattended while the smelting process is underway.
  • Immediately turn off the microwave if any sparking occurs or if a crucible breaks. If you cannot reach the control panel, pull the plug.
  • Allow the microwave and kiln to cool before trying to deal with any type of spill.
  • Always clean microwave after use.
  • Do not attempt to fire materials other than listed in these directions.
  • Use common sense during this process, always wear your protective gear and the world will be great.

 

DISCLAIMER

No guarantee is given on the amount of gold or silver obtained from this process, as it depends upon the quality of your material to begin with. The kiln is not a toy and is not to be used by children. IT IS A KILN THAT ULTIMATELY GENERATES TEMPERATURES IN EXCESS OF 2300 DEGREES! Please do not allow small children in the same room when you are firing! Use at your own risk and follow all recommended and common-sense safety precautions! Sellers are not responsible for accidents or injuries caused by hot kilns and your using one purchased from this seller acknowledges that you use it at your own risk. Please remember that a traditional kiln is composed of fireproofed materials and a microwave oven is made of materials that can burn under certain conditions.