I cast from several hundred to a few thousand pounds a year. I've been casting lead, and other metals, in one form or another for about 40 years
I wrote this up for Diverlink a while back
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A cast iron pot will work well, or even heavy aluminum pots if you are only doing one melt & can keep the bottom covered with molten lead. An old propane tank properly cleaned and sectioned also makes a pretty reasonable large capacity low cost pot. Anything used to help with the melting process, as well as the melt pot, should be relegated to that use permanently! It is not possible to clean a pan used to melt lead well enough to ever cook food in it again! The same applies with skimming tools and ladles. Even if they should look clean, the traces left behind are highly toxic and can cause permanent damage to your brain and other organs. Soup ladles, or tomato cans with a pair of vise grips serving as handles are good to handle the molten lead from the pot to the mold. A “standard" soup ladle holds about 3 pounds of lead. A “large” Tomato sauce can will hold about 12 pounds before it gets difficult to control. If pouring more than 12 pounds in a single shot make a bottom drop pot.
You can make molds from dry hardwood, an aluminum or steel cookie sheet with four side walls (if all you want is sheet), dry sand, or even plaster of paris if you bake it good and dry before adding the lead. Production molds are generally machined or cast aluminum, steel, or gray cast iron. If making a mold you intend to re-use allow for about 1.5° draft to get the lead out of the mold. Global Manufacturing makes semi-commercial molds at a reasonable price. No matter what you use as a mold, giving it a good coating of dry film graphite or molydisulphide will make it a lot easier to get the lead separated from the mold. Separating the lead from the mold should be done as soon after it fully hardens as practical to minimize difficulties “knocking out.” Silicone spray also works as a mold release agent, but burned silicone smells bad and the odor lingers on/in the weights for years.
Cast weights for the pocket style neoprene belts will be almost exactly half the size of shot weights for the same weight. Remember that smaller size = less drag.
Any stove, including some camping stoves, should be able to generate enough heat to melt the lead, which takes approximately 500 -700 degrees Fahrenheit. The “lighter" the lead (i.e more tin in the mix) the lower the melt point. Pure lead melts about 720°F. Solder, which is ~40% tin, melts at about 500°F. The "cajun cookers" are great heat sources for melting lead, plus once you're through doing the lead you can use the burner to fry turkeys and boil crabs, lobster, or mudbugs!
In any case always melt outside with good ventilation.
Lead sources:
1. Tire stores. The weights used to balance wheels are a lead-tin alloy and contain about 5 - 8 % antimony, which is a hardening agent, The result is castings which are much harder and more durable than lead or a lead- tin alloy. Most tire shops don't reuse wheel weights and will be happy to give you all you want as it usually costs them to have the weights taken away. They melt and cast well but the steel clips can be problematic to remove. The easiest and best way to remove them from the pot is with a magnet. The steel will float on the top of the molten lead and can be removed clean by using an old speaker magnet or any other magnet strong enough. Try to keep the lead dross (the other stuff floating on top of the lead) separate from the clips. The clips can be recycled as steel, but only if there is no lead mixed in with it. Wheel weights normally melt between 500 and 600 degrees F.
2. Hospitals. Hospitals often use radioactive tracers or drugs. These are shipped in virgin lead containers often weighing several pounds or kilograms each, and there are other protective parts to disposable delivery equipment that are also made of virgin lead. If you just need a few pounds (50 or less) contact your local hospital's radiology labs and offer to take the "trash" out. If they balk, you may even have to offer them a few $. This lead melts around 600-700 F (the highest melting point of the lot.)
3. Shooting ranges. This lead recovery is a lot of work. There is usually a lot of brass and copper to be cleaned from the spent projectiles and the amount of dross is almost as much as the amount of lead you'll recover, but it's cheap.
4. Plumbing contractors. Roof flashing and old lead caulked sewer pipes are constantly being replaced and are normally available, as is the lead sheathing from buried telephone lines.
5. Scrap yards. Most metal recyclers will sell scrap lead for melting. It can be in any of the above forms, plus ingot, 5 lb. pigs, and sheet. Scrap yards will often charge you twice what you could get the lead for if you scrounged a bit yourself. As a gauge, expect to pay up to $.40/lb for scrap lead at a scrap yard depending on how clean it is and how much is needed. In over one ton lots the price should be down around $.15-.20/lb
6. NEVER melt down a lead-acid battery to get the lead out of it! Some of the alloying elements are deadly (cadmium and arsenic for example) and they will boil out of the molten metal at about the same point the lead melts. This is not a good thing even if you are melting in a high wind with lots of ventilation.
If you have a choice you want to get the highest weight to surface area ratio stuff you can find. Not only is lead oxide hard to reduce back to metallic lead unless you know exactly what you are doing, handling it is the most toxic part of the entire operation.
The following procedures should be strictly followed for your safety!
DO NOT VIOLATE THESE PROCEDURES AND WARNINGS!
1. Do the following in a very well ventilated area (read outdoors). A fan to blow the very toxic fumes of the melted lead and any impurities away from where you are breathing is strongly recommended. You do not want to breathe these fumes! Lead can cause permanent brain damage and is toxic. At the very least, stand upwind of the vapors and fumes.
2. Be certain that there is no moisture of any sort in the material you use. The pot, beeswax, and everything else must be perfectly dry. Any moisture in the pot will instantly turn to steam and explosively spatter molten lead everywhere! Treat this step lightly and you may bear nasty scars for the rest of your life.
3. Be absolutely certain that the mold is absolutely dry and free of grease, oil, moisture, etc.
4. Flux the lead for uniform results.
Fluxing is the adding of a material which helps the alloying metals mix together and to float impurities to the surface for removal. If you melt a lead alloy, you will see a silvery scum on the surface of the molten metal. This scum is lead oxide and tin. The flux will help the tin to recombine with the alloy and will cause the lead oxide to precipitate in an easily removed form. Beeswax is a commonly available fluxing agent, however there are other commercial fluxing agents usually available from bullet casting supply houses that do not smoke or flare as much. Almost any hydrocarbon with a high flash point will work for fluxing. Old frying grease, crankcase oil, parrafin, “axle grease”, lard, etc have been used with success. These lower flash point materials will ignite and flare! Never the less the low flash point materials will still function as a flux if you are working in an area with nothing flammable overhead where the flame can be tolerated. With beeswax, about 1/4 teaspoon stirred into a 20 pound pot is all that is needed to clean up the alloy for pouring, although it will smoke a lot! Repeat fluxing and skimming until the mix is clean.
5. Add about a pound of 50/50 or 60/40 solder per 50 pounds of pure lead to have some tin in the alloy. This will allow it to flow more easily and fill the mold uniformly. The target here is 1% to 1.5% tin in the final alloy. More than that simply adds cost and lowers the melting point without giving any flow or strength advantage. Wheel weights generally start with enough tin. Sheathing and shielding don't.
6. Pre heat the mold by dipping a corner of it in the molten lead if the mold is small, or by filling a larger open mold very slowly. The first shot or two out of any mold will generally go back in the pot as a mold preheater with an incomplete fill. The preheating process provides two advantages. The first thing it does is slow down the set process to allow a more complete mold fill and better surface finish on the cast weight. The second thing it does is raise the mold temperature slowly to above boiling point, thus ensuring a dry mold.
7. Wear eye protection, goggles or a full face shield.
8. Wear a breath shield or mask, the thicker or more effective, the better. You could even breathe from your regulator and tank if the hose will reach.
9. Wear thick gloves, heavy welding gloves are best
10. Wear heatproof clothing. Heavy cotton absorbs sweat that will quench most small splashes before it reaches skin. NEVER wear synthetic fabrics, other than kevlar, when doing any hot metal operation! Any splashes, spatter or slag will melt the clothes and bond the hot metal to your skin for a REALLY nasty burn. Peeling off the melted plastic usually takes the hide with it!
11. Be aware that if the molten lead spatters or spills, it will stick to your skin and/or clothes and can cause some nasty burns.
Watch your heat! Lead, and the alloying elements in it, all have a vapor pressure once you get them molten, and the hotter the melt the higher the vapor pressure. The high vapor pressure of the alloying elements in batteries is the primary reason to let the big smelters deal with recycling them. As a rule of thumb, you want to pour lead as close to the melting point as you can, without having it set on you before you get the mold full.
Another rule of thumb is that when stirring the pot you should use a dry pine stick. If the pine stick chars to black in a few seconds, or if it ignites, the pot is too hot. Either turn off the heat or add a bit of cold lead, the faster method of the two, which will get it cooled down fast.
Boiling lead is not a good thing! If the top of the pot starts to turn yellow or gold you have the same problem of a pot that is overheated.
Remember that even after the lead hardens it is still around 500F and will remove skin if you touch it too soon. Good leather gloves are a must.
A final note: Lead dross is the stuff you skim off the top of the pot. The steel of the wheel weight clips can be recycled. The rest of it can be incorporated in a marker buoy weight by mixing it with cement and using the lead dross as the aggregate. Lead dross of any amount is NOT to be discarded as trash in the US. If you can't use it as ballast in another project, you are required to ship it to one ofthe metal smelters for reuse. That shipment is expensive as it has to go as a hazardous material. Metallic lead is dangerous if it splashes on you or hits you at high velocity. Dross is just plain nasty biologically. Dross encased in cement is rendered relatively harmless.
