Well these pics worked as a test so here we go again...... This is the small furnace I have made, based on the basics from this vid . I researched for quite some time before this build, furnace building can be as rough as guts or effective, thought out and functional. I have adapted a 9kg LPG blacksmiths forge build and applied to my needs for smelting. This build is fairly easy and within the ability of the majority, your safety on the other hand is up to you alone if utilising such equipment. I have used this type of design as I do not need to smelt 4kg crucibles, both for safety as I do not feel comfortable with vertically rising 1300c heat direct from the chamber, vertically lifting molten metal at bone melting temperatures and ease of handling by not having to double handle and switch to pouring tongs. I use this for melting silver cement from acid digestion recovery/refine, mostly for doing large runs of shot production before further processing by the silver cell, after which comes the bar pours. I can fit 3, 1Kg Morgan Salamander Crucibles comfortably if needed, this is my general use crucible I also use Fused Silica Crucibles and Melt Dishes, generally i usually stick to one at a time for economy. My LPG cylinder was bought new off the shelf from BCF to avoid explosions while in manufacture stages, larger than the usual 9kg cylinder at 10kg so I get a smidge bigger chamber area lengthwise. Considerable research went into this design with consideration given to chamber size, Burner size and BTU output, Burner design, melt size required and refractories used. You could easily adapt this same design for a vertical furnace build for a larger crucible and 1" Burner. The ceramic fibre is made by Unifrax type: Durablanket Zircon 2400F heavy weight 1" blanket. I have used this due to the fact it is a high grade blanket and I would encourage you if are inclined to such a build to use the best quality blanket you can afford. Why didn't I use a poured refractory cement or firebrick lining?? Two reasons, 1: Weight of finished unit, 2: Economy. Ceramic fibre is extremely light and an excellent insulator and refractory. The chamber attains melt temp in a very short space of time compared to a castable or firebrick lining, instead of acting like a heatsink, I am poring while a castable/firebrick lining will still be attaining working temperature, this dramatically reduces fuel cost as I do not need to run this all day long, I also chose Ceramic fibre for ease of maintenance. This design utilises 2 layers of 1" ceramic fibre, after the inner lining has had its day, I can simply remove it without the need to replace the entire refractory lining. I have not used a sodium silicate sealer on this unit, the entire inner exposed ceramic fibre surface is sealed with a zircon based refractory ceramic wash coat. The sodium silicate is used also as a rigidiser, if you use a high grade/density blanket the lining is easily firm enough without it. Any exposed fibre surface MUST be coated in rigidiser the stop dissemination of microscopic fibres while operating if you have designed in such a way as to not seal the entire surface with a refractory wash coat. The wash coat I used is called RTZ wash coat, and is a ceramic zircon based paintable or spray able water based refractory. I am not 100% happy with it due to firecracking but it is effective. My research showed the best you can get is called ITC100HT, it is very exy compared to the RTZ, it is US made and not available in Australia anywhere. Apply the wash coat in light coats, you can spray the ceramic fibre with water before applying to help application, I used a brush but you must thin down the wash coat or you will tear the fibre blanket to bits. It will take a week or more to cure, Do NOT get impatient with its curing time. Both ends of the cylinder are lined with ceramic fibre, as I designed this as a sort of Furnace/forge/kiln crossover, I used a bubbled alumina firebrick as the floor, these are substantially more expensive than your average firebrick that you will find, but are not heavy heatsinks like your standard yellow firebricks. This floor piece is easily removable along with the inner lining when it comes time for replacement. The Burner is an engineered design not just your average hillbilly pipefitting effort you will find for both sale and all over youtube. It is made by Thermal Art Design type JF#1 3/4 inch. It is a Stainless steel made burner with a replaceable flare if need be. It also has an adjustable choke, a must for any burner, you can adjust your flame -Oxidising, Reducing or Neutral. Beware of what you see on youtube, by far the majority of these idiots have no idea what they are doing regarding burners, they think you can just screw a few bits of pipe together and away you go.....WRONG!!!! I will leave it up to you to do your research on this topic, one of the best resources I found was a site called Hybridburners. This site covers many of the scientific areas regarding Forge design and is directly applicable to what you will need, research it well. My fuel tank is your usual 9kg LPG tank. I run a CIG edge regulator at 10-15 psi for silver and 20-25 psi for gold. From the regulator the fuel hose runs to a gas tap ball valve just in front of the Burner, I do not have a need for an idle circuit nor a secondary needle valve. A word on safety: Unless you use serious safety gear forget about using this sort of equipment and stick to your torch and dish. When you open the front door just before you extract a crucible the heat is extreme, welding gloves will become hot in an instant and they will burn you, leather is not a sufficient insulator, the heat will flow straight through and you will feel it just when you have a full molten charge in your hands. I use Foil backed Aramid gloves with an inner Wool felt lining, they are molten splash resistant and elbow length, use a splash apron as well, face shield and leather boots. There are no second chances with this method of smelting. Your safety gear should reflect the respect you have for your own life. Molten metal burns can be life changing, a molten flux burn is Toxic and worse than molten metal. Use your noggin and enjoy. I will upload some more pics when I have time.
Nice first go JNS, did you use pure refined silver? The finish on the bars is not too bad, at least they are shiny in the mold and not frozen and oxidised. I fired up the furnace last week and poured over 2 kilo of silver shot in one session, got into the process a little much and totally forgot to take pics. I nearly have enough refined once shot on hand to bother starting up the silver cell for a final refine process. Will have to hit the forum for some more material soon to keep the cell fed though, got some Karat Au to refine now and will post those bars when done too.
Hi BenKenobi, i used scrapped silver made from sterling. I am experimenting by using steel moulding covered with cast iron. I do not have a furnace yet. With the use of oxy-acetylene torch, the melting of about 500 grams was carried out. Probably next year, i am planning to buy a mini furnace and graphite moulds. Here is the mess that i made which turns out to be ok.
Had a crack at some hand pours. Turned out better than I thought. Small bar is 2ozt, bigger one just under 5ozt. Just waiting on some stamps to arrive and some other shape molds. Bars were poured from shot made from a 999 kilo bar. There were some small specks of borax on the 5oz bar that I chipped off, any ideas how to remove borax without marking the bar? These are as is straight from the mold. Look forward to any comments/advice
I have no idea of your experience level so please take the following under advice according to it. Are you quenching your bars in clean water after the pour? this normally eradicates borax beads if the bar is still hot enough due to sudden contraction. If not there is a solution and a recommendation I have. Solution: Sulphuric acid dilute pickle will dissolve borax. Immerse into pickle AFTER quenching in water. The process is accelerated if the bar is still warm. Recommendation: Is subject to the amount of borax in your melt dish, only use enough borax to seal the dish, no more, you already have a relatively pure product assuming no contamination from the previous melt and reducing to shot if using 999 bars. Do not add borax to your melt, it is simply un necessary and leads to the issues you are experiencing. Assuming there is an excess, heat the dish, melt the borax, use the flame pressure/temperature to manipulate the molten borax and blow it out of the dish at the lip or pouring spout if you have one. Concerning your melt dish, use ONLY a new dish for refined silver at 999 bullion grade, if not, you have already reduced the fineness of the end product by simply melting in a previously contaminated dish. Metal beads, oxides and other foreign contaminants will reside in the flux after any process otherwise, your 999 will no longer be of guaranteed fineness.
I use pickle, which is basically dilute sulphuric acid, as per Ben above. If that is too much hassle, run it under hot tap water or if persistent put it in an old pot and boil it.
What do people do with these hand poured bars? I have 5 oz bars made from 999 coins that I have no need for lol
My first attempt at hand pouring silver. I carefully glazed a new melt dish with a small pinch at a time and looked like there was no excess, like you said- just enough to seal the dish. Out of the half dozen or so I've poured so far, that was the only one to have borax beads. Maybe i left too long before quenching in clean water. How far do you dilute the sulphuric acid/water mix? 50/50 Thanks for the advice BenKenobi I'm enjoying hand pouring silver and will post some pics as i go.
Ill try boiling, see how that goes before i get some acid. Thanks for the tip I treat it as a hobby, it helps i guess if you already have half the gear. maybe one day i might put some up for auction here to see if there is any interest. Thanks
Id like to try different surface finishes. If once the silver is poured into the mold, if I left the flame on the surface, would that give a smooth polished look? Here's one from the same melt dish I started with. No borax beads on this one
My issue is who would I sell it too? Don’t get me wrong I had fun, but now have 20 ounces of home made 999 bars of various sizes and another 10 ounces of 925 or better bars lol.
I'm sure there would be a market for these bars. I thought they would be popular, something different than the mass produced stuff. I'll pour a few more and try my luck selling them here, if there's no interest, that's ok by me. Put one of yours up for sale, you might be surprised.
Decided I will share a quick pick of my silver cell, showing crystal silver growth before I knock down the crystals a bit to avoid a short while the cell is un attended. This the Seventh step in my refining process, there are a few secrets I have had to learn over the years by trial and error so I will not be detailing anything specific to operation, that information can be discovered by yourself by studying and research on refining operations. Before anyone gets any hair brained ideas, let me advise there is significant investment in the setup as many experienced in this already know. As a hint there is over 500grams of PURE silver in the AgNo3 electrolyte alone, which must be replaced when contaminated with other metals before co deposition occurs, or you will definitely not be achieving the purpose for which it is intended. The Amperage and Voltage are also strictly controlled or you will also co deposit unwanted metals. This is 99.99+ purity in action. You may not be able to tell from the pic but the electrolyte is actually in the cell covering the silver crystal.......Clean and pure
