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Thread: New guy in WI

  1. #1

    New guy in WI

    Hi everyone, My name is Paul and i'm just starting to melt some stuff. I've been lurking here reading for a while, watching videos, reading some books by a guy named Ammen, and i just got enough of a push to sign up by a member i know from another forum. I just have a small charcoal foundry similar to the mini-metal-foundry video by some guy on youtube and i have successfully made a few aluminum muffins, as well as a smaller copper blob (didn't have enough to make a whole muffin). My goal is to be able to melt copper into ingots, and then into things via sand casting. Nothing big, nothing load bearing, nothing that has to contain pressure, just small shiny things as a hobby. I'm interested to learn all i can about bigger, more complex projects, but i don't foresee myself doing anything beyond mostly ornamental stuff for the time being.

    The reason I'm shooting for copper is because i have a lot of the stuff. I'm encouraged by the fact that i did melt some of it, but it wasn't very efficient. My process was basically to put a bunch of hard lump charcoal into my mini foundry and blow air in through the side. While it got hot enough to melt the copper in fairly short order, i would run out of charcoal inside before i could melt very much of it. The charcoal seemed to burn up and blow out the top fairly quickly, and a bunch of it would fall into the crucible on the way out, filling the pool of molten copper up with junk. I probably lost 2/3 of it to a giant lump of ash/copper in a concretion.

    So my initial question is how to improve this system. I could shape a lid for the crucible out of sheet steel to keep the ashes out (and maybe keep the oxygen out), or I could use a different fuel. I got some briquettes advertised as "more airflow, higher temperatures", i think it's mainly due to the shape having more surface area. There's a video of someone using briquettes to melt brass, do you think with enough air it could melt copper? I'm hoping the lower spark/ash output of the briquettes would help keep the crucible from getting too contaminated. I also found a place somewhat nearby that sells anthracite in case i need to go full-coal, but i'm thinking my rapidly-decaying sand/plaster lined foundry may hit a wall here pretty soon if i keep pushing it. Any thoughts/tips/suggestions are greatly appreciated, i'm just a hack who made some aluminum muffins on his driveway so i need all the help i can get! Reading this forum has already been hugely helpful, so thank you all for that.

  2. #2
    Welcome to the Avenue! You may want to figure out a way to turn your air down, believe it or not. From what I understand, you don't need a lot to get the same effect. A simple way to regulate your airflow is to add a tee into your air intake, just before it goes into the furnace. put your blower into one side of the tee, and block the third side of the tee with a moveable disc so you can let some of the air dump out instead of going into the furnace. Adjust it until you get a steady burn, without a volcano of ash and embers fountaining out the top. After a certain point, adding more air does nothing for the burn. Don't use the briquettes, they produce a lot of ash, stick with the lump charcoal. To add more, just pick up on your crucible a bit to allow some of the burning coal to fall further in, and add more around the crucible. Depending on the crucible, you should easily be able to melt copper with charcoal, it was done for thousands of years before we came along. You may want to think about making a lid for the furnace instead of the crucible. Hope this helps. Oh, pictures, we liiike pictures.
    Vade Libram Harenae.

  3. #3
    Thanks for the tips! Pictures and video are incoming. I do have quite the shower of sparks out the top, perhaps I do have too much air. I'm using a hair dryer that has two settings, I used the strong one to try to melt copper. The low setting worked for the aluminum, but I think it's way less air than high, perhaps too little. I like the idea of the regulator, I hadn't thought of that! I could find a level between the two. It's a pretty cheap hair dryer, and I assume that my wife saying "the hair dryer smells funny now" is her way of saying I wrecked it and it's now mine. So I'll have to make it work.

    I do have a lid for the foundry with a small hole in the top (3 inches) which is about the inner diameter of the crucible I'm using. I'm using a clay graphite crucible from Amazon, though I think it may be too big. I don't remember the exact size but I can look it up and get back to you. There is enough room for a layer of charcoal under it, but if it raise it too much then the foundry lid sits on top of it. There isn't a ton of wiggle room, which is why I think it may be too big.

    I was quite happy to get the copper to melt, but it got gunked up so quickly too! Is there something I should add to it? I've seen people ad borax in videos, so I tried that and it didn't seem to do much. Too little too late probably.

  4. #4
    Ok i said pictures and video incoming, so here's one of each. First, the aluminum pucks and blob of copper i melted:

    they aren't all that different from other ones i've seen online, but i'm still proud! The little lump of copper feels surprisingly heavy for it's size, but i've never held any copper that wasn't a penny, wire, or pipe. At the same time, the biggest aluminum puck feels surprisingly light! I guess that shouldn't come as a surprise. I haven't cut into them so i don't know what kinds of porosity they have. The bigger of the aluminum pucks were the last ones i made, and i did do some fluxing, but no degassing. following what i read, i didn't leave them melted for very long, i just melted them to liquid and poured somewhat quickly. I wanted to go for bricks more than pucks due to the more efficient way they can be stacked on my shelf, but a muffin tray was all i could get clearance from my wife to destroy, so that's what i used.

    If you want to see the foundry and watch me using it, watch this:

    You can see the actual showers of sparks coming off the top nearly up to my head! In hindsight I think you are completely right about too much air. Still working on getting some additional equipment like proper crucible handling tons and the like, but i couldn't resist trying it out when i had the chance. I used to be a graduate student for years so i can devour books and articles (and forum posts) pretty well, but nothing is more fun than diving in and giving it a go!

  5. #5
    hey rufled, welcome to the forums! I loved your video and got a seriously good laugh from the commentary, lol.

    If your really serious about melting copper, I really dont think charcoal is really the best way to go in all honesty, I would go with a propane burner like a forge burner in the furnace, and maybe better lining. Copper is actually really hard to melt imo and Ive honestly never really been able to successfully pull it off myself, but I plan on trying again here soon. As oddduck said above, you might be giving it a little too much air from the hair dryer and might need to tone it down a little.

    I like to take the hair dryers apart and take the fans out of them, which are 12v DC fans, so you can hook up one of those wall outlet adapters up to it that has the switch to switch between different voltages, we all seem to have one of those things floating around somewhere, but can never find it when we actually do find a use for it, one of those power supplies. The heater wires, I usually straighten out and put on a spool, and the thin stuff, I use with my foam cutter to cut out foam shapes to use for lost foam casting. If you take a little sandpaper and some time with some 2 inch pvc pipe couplings, the fan will fit perfectly in between two of them and make a really awesome blower for charcoal furnaces, and thats how I ran mine for a few years when I was using charcoal in my mini furnace.

    Like said above, I would stick with aluminum for now, and when you upgrade your furnace and go with propane/oil burners, you'll notice a massive difference in time of melting stuff, and ease of use. I used to take 15-20 mins to melt a few pounds of aluminum, and after I built my new furnace and oil burner, it's around 3-5 minutes. Copper requires some seriously high heat to melt it like you said above, and if you add any metal to the melt, it'll want to cool it to the point it wants to solidify it, which is a very good way to damage a crucible, same with using pliers on them or leaving metal in them. You always want to get the metal and everything out of them at the end of the melting session. If you try heating up a crucible full of solid metal, the metal will want to expand slightly and will crack and destroy your precious and expensive clay graphite crucible.

    I wouldnt add borax to your melt yet, thats only for when you can get to the point that you can melt a full pot of metal or a decent amount of it. Borax is a very aggressive flux and tends to eat away at your crucible, I tend to use boric acid, which isnt as agressive, but still works just the same and wont hurt the crucibles as bad. Boric acid can be found at the dollar store as the big yellow bottles of roach killer, you can find them for really cheap. The point of borax and boric acid is not only to act as a flux for the copper/copper alloys, but also to melt onto the top and act as somewhat of a cover to prevent the alloying metals that your melting from oxidizing and burning off. Some people add some broken beer bottles with it, to act as a glass cover to prevent the oxygen from reaching the metal, but Ive never used it.

    If you was wanting to make some things for just playing around and such that isnt ingots, I would look into lost foam and making yourself a little foam cutter, for people just starting out, it's the best way to start making things imo. Also, the reason most people use muffin trays is because it's just an easy way to make ingots, thats mainly it, its just the most convenient way to make them. I would also grab a face shield from harbor freight and some premium welding gloves, it helps a ton because they dont let the heat through as much as normal gloves, and they are much longer so they go part way up your arms and protect your wrists. The face shield is defenitely needed tho, you dont want a steam pop to happen when your trying to pour and getting shot in the face with flying molten metal. That'll end in a bad trip to the ER along with some nasty scars and knowing that you have part of your backside on your face.

    Also, your picture in the last post just went kaput, so just to let you know.

  6. #6
    Administrator Site Admin
    Join Date
    Dec 2005
    Huatulco, Mexico
    Copper is difficult to make castings from, even for the pros. It oxidizes badly during the melt, as you have discovered. That is why you lost much of your melt; the charcoal was not the problem. In fact, the charcoal on top of your melt is a good thing.

    Bronze is the best copper alloy for casting. You may want to sell your copper to your local scrap dealer and buy some scrap red brass from him. (The price of scrap copper is way higher than red brass.) Most cast pipe fittings and valves are red brass, which is also called "Eighty-five, three five." It's 85% copper, 5% zinc, 5% tin, and 5% lead. It melts and casts beautifully.

    When I die, Heaven can wait—I want to go to McMaster-Carr.

  7. #7
    Thanks for the tips! I'm probably going to keep messing around with the copper, but aluminum seems like the way forward with actually making stuff. I have some petrobond, I figure I'll use that until I can figure out what good sand should feel like. The Guide to Sand Casting book by Ammen talked a lot about sand qualities and mixes, but without touching it I had trouble figuring out what he meant by some of it. This petrobond stuff, though, I bet I could make one heck of a sandcastle with it! It seems like sand casting and lost foam casting should be another fun step with these aluminum muffins. Now I just need something to make! I have a few ideas, but I need to do some more planning/reading on that. I have been saving brass too, I just don't have a lot of it yet so I haven't tried melting it down. What makes it work so well? Is it the cooler temps or the alloy being more resistant to oxidation? I read something about zinc in brass bubbling up to the surface, does that form an oxygen barrier or something? I could always add a touch of zinc to the copper if that would help me get ingots out of this hard to melt copper. I'm not too worried about keeping it pure, like I said it's just for ornamental stuff.

    So for the copper, what would you suggest I try (before I give in and just leave in to mess with later, I mean)? I never thought of oxidation being the problem over the ashes flying into the crucible, and I hadn't considered that adding copper to the pool would solidify it. In that case, should I just load the crucible from the start with the copper I want to melt, get it melted quickly and pour right away? Speaking of borax, I saw one video where a guy added borax into the crucible with the copper at the start. Would something like that work, or should I wait until a pool is forming? I definitely had a pool in the crucible when it started melting, but it started to go bad in a very short time.

    Boric acid, borax, and bottle glass are fluxes for forming a surface coating to prevent oxygen from getting into the melt, correct? Is it hot enough to for bottle glass to do that? Because I would have to go buy boric acid, but I have some bottles in my recycle bin I could experiment with. I'm fully expecting this copper melting thing to not work for all the reasons outlined by you guys, I just want to give it another shot. So throw a chunk of bottle glass into the crucible with the copper at the start and pour right away when it melts?

    I have some aluminum questions. I've read cast aluminum is best, cans leave lots of crud because of the plastic liners and rapid oxidation, and extruded aluminum is a bit too soft, correct? If I had a bunch of extruded aluminum, would it still work for ornamental castings? Speaking of hardness, I've read an alloy of zinc and aluminum is pretty good stuff for casting, could I throw some zinc in with extruded aluminum for a similar effect? I have a bunch of mostly destroyed hot wheels cars that I think are zinc.

    Thanks for all the help so far, this seems like a fantastic forum. It's hard to find good forums these days.

  8. #8
    I wouldnt add the boric acid/borax to the brass/copper at the start, it tends to evaporate pretty quickly imo and is mainly there just to flux the melt and make it a little more fluid by removing the impurities and such in the metal, also it acts as a cover to prevent the oxygen from reacting with the melt. The reason rasper said that it is good to have a little charcoal on the top of the melt is because it'll react with the oxygen and tend to burn up and convert to CO2 before it can burn down enough to react with the metal, and limit the amount of molten metal that is exposed to the oxygen/air.

    Cast aluminum is the best to use and that is mainly because of the stuff that is added to it to allow it to flow and increase it's strength/various properties. Cans tend to be just like aluminum foil covered with a layer of paint and plastic on both insides and outsides of the walls of the can, if you try melting the cans, most of the time, you'll end up just burning the paint and crap off and it oxidizes the cans to almost nothing. Depending on the conditions and such in the furnace, most people get between 60-90% loss with the cans due to that. Extruded aluminum and cast aluminum have very little to no other alloying metals in them to help them flow into a mold and such where as cast aluminum has 6-12% silicon added to it to increase it's strength and ability to flow into a mold, and to help with shrinkage. Also, you can make an easier machinable aluminum bronze by adding cast aluminum rather than extruded aluminum, the silicon in it helps make it easier to machine.

    Glass bottles are usually made of soda lime glass, which the melting temp of that is around 1350-1400 degrees, much lower than the melting point of brass/copper, so it'll melt fairly easily in that application. Only thing to think about is that it tends to cover the crucible and you have glass stuck to the crucible if you dont scrape it off when your ready to pour. Most of the time, you would add the glass to the metal when your starting to melt it like you were thinking of doing with the borax above, the glass would stay throughout the heat where as the borax or boric acid would just boil off long before the metal would be melted.

    The zinc/aluminum alloys are usually called zamac, you would have to add like 75%+ of zinc to aluminum to make that alloy. If you really intend on using the extruded stuff, I know you can throw in some really small pieces of copper so you would have like a 5% by weight of aluminum to copper and it would help with the metal flow much better. Another thing you could do is make aluminum bronze, which you just melt the copper, and add around 5-10% aluminum by weight to the melt, and it'll melt into it making an alloy that looks like gold, very very strong, but very hard to machine due to being so hard/strong. I was planning on making some myself and making some swords or knives with it, mainly because I thought a golden sword or golden knife would be very cool, expecially when it's around 6x harder than mild steel if it's forged also.

    The brass, I would avoid doing for a while until you get the other metals and such under your belt first. The zinc in it tends to burn off in a white smoke and is what will give you the metal fume fever, so to cast that, you would need the boric acid and at least a P100 series respirator or at least a P95 series one. Those are designed for metal casting and filter out zinc, lead, cadmium, etc.

    The copper will easily freeze a melt when added to it, it acts as a massive heatsink when it is added to the melt, and unless you have the copper superheated, it'll just freeze it, which just ends in a bad day really. Most copper/aluminum alloys will do that tho, so you just have to learn to adjust for that with the amount that your melting, the more your melting, the more it'll want to freeze.

  9. #9
    Just a thought, are you using the same crucible for both metals? This is not a good idea, it will screw up either metal melted in short order if there is any dross or leftover metal in the crucible. It will make aluminum bronze of some sort or other and could explain part of your dross problem and the slower melt times. If you can swing it (trust me, I know what it's like trying to do this on zero budget) get a separate crucible for each different metal you use. If you have any empty ones kicking around, cut the top off a plumber's torch sized propane bottle using a hacksaw and try that for the aluminum melts. Practically free, and they work okay with aluminum, and if you can find the skinnier ones it may give you a bit more room for charcoal. You will really want to watch the airflow if you use one, however, because too much blast will act like a cutting torch. Save the commercial crucible for copper/brass/bronze.
    Vade Libram Harenae.

  10. #10
    for aluminum, I usually just use a steel crucible, just find some steel pipe where the walls are 1/8th inch thick or slightly more, and have someone weld a piece of 1/8-1/4 inch steel on the bottom of the pipe, that'll make one of the most reliable crucibles that you could find for melting aluminum. Ive had 20-30 melts on mine, and have done brass in them too, (different crucible than the ones for aluminum) and they're still as good as they were when I made them a year or two ago. Ive found the propane tanks tend to be pretty thin really and will burn through fairly quick in a charcoal fire where the air isnt controlled just perfectly.

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