Slysmith Posted May 18, 2009 Share Posted May 18, 2009 I am trying to make my first furnace. I'm sorry if I mangle the proper words, so please correct me if I use terms improperly. I'm using a 5 gallon popcorn tin and giving it about a 2 inch refractory around the furnace of 5 to 1 Perlite to furnace cement. I cannot find fire clay locally, but since I am planning to melt only aluminum in this furnace and I'll start with a steel pipe crucible, I am imagining it is alright. I cannot find much aluminum locally, so I'm afraid I will have to deal with the massive amounts of dross from aluminum cans. I was able to melt a can with just some charcoal, and I estimate over half was dross. I made my own Oliver-upwind burner from steel tubing, but when I tested it, the flame seemed to be burning INSIDE the burner about 2 inches from the place the propane is injected. I thought the majority of burning was supposed to take place at the end of the pipe. End of the pipe got seriously hot in just a minute of burning. I'm going to have a steel pipe that holds the burner (whats that name of that? Tweer...?) and the flame AUGHT to coil around my crucible. The center open area will be formed as I squish my refractory around a sheet of duct taped aluminum sheeting. The bottom of the furnace will have a slight funnel dip if my plastic tub bottom holds its shape as I squish refractory around it. I'll have about a pinky sized hole in the bottom too and any spills aught to pour out the bottom in theory anyway. Is there any design flaw in what I am trying to do? Is 2 inches thick good enough? Am I in danger of slumping with these materials? Have any of you built a propane furnace out of these materials? I aught to be ready to mix a touch of water with the furnace cement soon and then I'll try to get the moisture out over several days. I saw somewhere that I want the furnace to dry SLOWLY? I understand that I don't want to fire it up after 48 hours drying time (except maybe in short bursts) but do I really WANT the refractory to dry slow with plastic wrapped around it? Is there a danger of cracking if the inside dries to fast or what? Anyway, for you folks that are more experienced than me, please offer some advice on where I might screw up or if I need to change anything. Thanks for your time. Quote Link to comment Share on other sites More sharing options...
Charlotte Posted May 18, 2009 Share Posted May 18, 2009 I'm not entirely clear on your design. It would be helpful if you posted drawings. As for melting Aluminum and fire clay: Look locally at your brick yards and get the fire brick that is used for chimeny building. I don't recommend mixing pearlinte with mortar in the use you are planning to make of it. That grade of fire brick can be used in an unmortered stack to surround an aluminum crucible. One of the big time metal sculptors I know uses a loose stack of higher temperature fire brick to melt 50-70 lbs of bronze at at time. Cast furnaces and blacksmith forges are really two different animals. There is a lot more to working with molten metal than you may realize. There are many safety issues that need to be addressed. I'm sure that some of very experience metal casters will chime in on these issues. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted May 18, 2009 Share Posted May 18, 2009 Does this type of burner use a blower? What type of regulator are you using with it and at what supposed pressure? Quote Link to comment Share on other sites More sharing options...
Dodge Posted May 18, 2009 Share Posted May 18, 2009 I agree, pictures, drawings etc. would be helpful in diagnostics. That being said, NONE of the flame should be burning inside the burner. ALL of the propane should burn outside the burner nozzle. I had the same problem and found the air:fuel mix was the culprit but without more info on your application, it would be near impossible to diagnose. Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 19, 2009 Share Posted May 19, 2009 The "Oliver Downdraft" is an ejector burner similar to a primitive Porter, type 3 maybe. I don't have a copy of Mike's book and he didn't have much to say about his earlier types but I think they're similar. Anyway, properly tuned it'll do the job though there are much easier burners to build and tune. A naturally aspirated burner will work in melters for sure. Robert Grauman or a buddy was melting 30lb batches of iron with a 1 1/4" Sidearm in a reasonable time. I wouldn't use perlite either, it melts at 2,000f so even bronze will erode it quickly. For the time and effort a commercial refractory is the only way to go. In my opinion anyway. A person CAN make a furnace to be both a forge and a melter but they're not great for either. It's the old, "a tool designed to do everything, doesn't do anything well," rule. Frosty Quote Link to comment Share on other sites More sharing options...
Quenchcrack Posted May 19, 2009 Share Posted May 19, 2009 In the event you actually do get some aluminum melted, sprinkle in a few teaspoons of Potassium Chloride, the salt substitute you can buy at the grocery store. It will scavange the dissolved gases in the molten aluminum and reduce the pin holes when the metal solidifies. I assume you will do this outside? If not, do not mess with the KCl, it will form chlorine gas and that is not a good thing to do inside. Oh, and have you ever seen what happens when you pour molten aluminum into a crucible or mold that has a bit of moisture trapped inside? Ever seen Old Faithful? Learn about safety FIRST. Quote Link to comment Share on other sites More sharing options...
Slysmith Posted May 20, 2009 Author Share Posted May 20, 2009 (edited) Ok, Yes I did do poor job on the descriptions. My burner is easy to see if you google "Oliver upwind burner" (first hit). I drilled a #57 hole in a brass tube and it ejects gas to the side and into an 3/4 inch steel tube. I made a flare out of the same kind of pipe but it was an adapter that goes up to 1 inch. IF you see the 3 holes on the side, the third hole has the blue propane flame just visible and that means that I have burning propane for about 4 inches INSIDE the tube. That kind of bothered me even if steel is not the best conductor. For the er... tweer (tyuver? whatever the place for the burner) I have a steel pipe I will put inside my popcorn tin and set the burner inside of. This of course has no blower since the propane does the job. I have a single setting (unadjustable) 20 PSI adapter for the propane. Kind of regret not spending the extra for the ajustable. I wasn't planning to USE this as a forge, but perhaps if the mood struck me and I had not found firebrick. For a forge I planned to use a stainless steel sink with one side water and the other with a blower, refractory and grog lined sink (as seen in pop sci recently). THAT is still some time down the road (gotta find some kinda anvil if I'm gonna pound metal). HEY, is it possible to buy crumbled up grog (broken firebrick)? I could use a bag of that stuff. I just can not track down any freekin refractory other than the fireplace repair cement stuff from a hardware store (not Portland). I know there is a place about an hour away where I should be able to buy firebrick, so I'll go visit there this summer. I will use good refractory for a good furnace once I have gotten the low temp (relatively) of aluminum down pat. I certainly won't be melting brass in this thing. Maybe lead and aluminum (zinc if I get the breathing mask working), but not much higher than that. Oh and of course I'd never burn this inside. What kind of a nutjob (I'm sure there are many newbies) would do this inside unless it was in a warehouse. I'm planning to create a sand pit once I get started. I did not know the Potassium Chloride trick. I'll be certain I make my charcoal filter mask first to avoid the chlorine gas. BTW, where can one FIND activated charcoal? Oh and I know all to well about the gas laws.... Yeah too moist a casting would be terrifying. Anyway, I was just wondering if there was any glaring stupid errors before I got started. Is two inches enough insulation? I'll try to get some pictures up and running... Maybe even tonight. The lid will be a bit tricky it seems. Dodge, if you would look at the oliver upwind burner, and if you think the burning of the flame is taking place too deep in the burner, please give me an idea how I might slow the mixing down. I mean I guess I could try to cap the end so that less air is sucked in and perhaps form some kind of sleeve of steel to reduce the air from the sides. I made it pretty exactly as the design calls for, so I was surprised that I had the burning IN the tube and not at the flare. Thanks for the help. I really need to be prepared for the possibility of steam. I was not worrying about that, so I appreciate the warning Quench. Thanks guys for looking over my ideas. I'll try to show where I am in my progress as soon as possible. Edited May 20, 2009 by Slysmith Quote Link to comment Share on other sites More sharing options...
Charlotte Posted May 20, 2009 Share Posted May 20, 2009 (edited) Ok first things first: 1) Refactory, Atlantic Firebrick and Supply Co in Jacksonville Flordia. 2) Have you checked for fireplace firebrick at local brick yards? It is all you need to melt aluminum. Just dry Stack and heat crucible through a gap in brick. Very simple, low cost, gets the job done. Puts the crucible and fire on the ground where everything can be safer. Depending on your water table and local geography you might even be able to dig a pit and put the whole thing in a pit. That is the favored place for most melting furnace that I know of. 3) Re think your design of burner. Something is not right with your setup. Read all the Gas forge stickies at the head of blacksmithing. Look I have an AP Green distribution warehouse 20 miles from this computer. If I were going to do what you seem to intend, melt aluminum, I could set the whole thing up for about a buck and change for brick and $18 in pipe fittings and widggets. I would be able to go to any brick yard and pick up what I need. I'd be worrying about how big a crucible I wanted, what I was going to handle it with, what I was going to do with the molten aluminum once I had it, and last by most importantly, how I was going to make sure I didn't scar or cripple my self for life playing with a process I don't really understand. Edited May 20, 2009 by Charlotte add sentence Quote Link to comment Share on other sites More sharing options...
Slysmith Posted May 20, 2009 Author Share Posted May 20, 2009 So, use the brick that are used in a fireplace. Interestingly I have never heard that suggested in all the time I have spent lerking about thinking of melting metals and casting. Pipes for chimney flues... sure, but not the BRICK that are used in fireplaces.... Very smart. There is a brick company about an hour away and I did not think about just getting brick for a fireplace and not actual firebrick (I forget what firebrick are made of, does anyone recall what the elements are?) Oh and yes, the pipe I got and made the burner out of is in the ball park of what you mentioned. The pricey bit was the xxxx regulator to get the right pressure. I may really have to have something that allows me to move the furnace around and I can't see the wife letting me build a brick furnace in the back yard. BUT I might could use my in-laws place... they have a ton of land. Hmmmm... something to really consider. By the way, I have heard many folks talk about one form of refractory adsorbing heat and others reflecting heat. Can anyone comment on this? Clearly I'd much prefer to reflect heat and conserve energy. About Crucibles, once I step above using a steel pipe, I have the art teacher down the hall that will craft me all the crucibles I want.... That is if ordinary redware clay is up to the task? Is there a different clay from the ordinary pottery clay that would need to be used? I know the shapes are different, and walls pretty thick, but will ordinary clay work for aluminum ok? How about iron and steel one day? Ceramics pretty much withstand heat far above ordinary melting points right? (I'm not planning to melt tungsten). For tools I was probably going to just get by for now with my own custom crafted junk and then if I made a forge, I'd bend some metals and craft the fancy clamps etc. needed to actually grasp crucibles evenly. Moving up to ceramic crucibles would give me a reason to make a forge and craft some tools. Oh and Charlotte, I have a friend's coat that is used by the guys that direct airplanes in the cold and it warns that the coat can catch fire and you wouldn't' be aware of it. I figure that and welders gloves will work till I can fashion a heavy leather apron. I have an old welders mask but I guess I'll use plain glass so I can see. I have one question no one has mentioned about safety. I have heard that long term exposure to the infrared spectrum can be damaging to the eyes. Is that in fact the case and do any of you use anything that filters that part of the spectrum out? Thanks again folks for all the help. Quote Link to comment Share on other sites More sharing options...
Charlotte Posted May 20, 2009 Share Posted May 20, 2009 There are some big gaps in your knowledge that we cann't repair this way. I STRONGLY suggest, since you want to start by casting, that you buy: "Practical Casting" by TIM McCreight Published by BrynMorgen Press, Cape Eliizabeth, Maine. Available on Most of the internet book sellers. I just replaced a damaged copy for $19.95 plus shipping The back of the book goes into crucibles, furnace construction, tools need to cast metals etc. It is aimed at the fine art caster but covers both jewlery and larger scale castings. McCreight's book "The Complete MetalSmith" is in many if not most Blacksmiths reference library. Quote Link to comment Share on other sites More sharing options...
Charlotte Posted May 20, 2009 Share Posted May 20, 2009 (edited) dbl post sorry Edited May 20, 2009 by Charlotte double post Quote Link to comment Share on other sites More sharing options...
Bentiron1946 Posted May 20, 2009 Share Posted May 20, 2009 Glad to hear that you have a brick yard near to you, they will have fire clay. My first melting furnace was a 5 gallon bucket with a sand/fire clay liner. I let it air dry for 3 days then patched all of the cracks with the same sand/fire clay mixture. Then I built a small wood fire in the thing and kept it going for a day and then patched more cracks and let them dry. The lid consisted of two fire bricks, like used for fire places. My burner was a forced draft affair that used propane full throttle from the bottle powered by a shop vac. This little furnace would hold a crucible large enough to hold about 5# of bronze. I made my own lifting tongs. Yes you should have some kind of UV protection after all the inside of this furnace is incandescent white when at the right temperature. DON'T mess around with shop/home made crucibles, your foot isn't worth a broken crucible full of hot metal breaking and spilling on it. My next furnace was made from a section of gas fired water heater lined with common fire brick. Worked very well for fifteen years using the same burner,same shop vac. I just upped the size of my crucible to one that held 25# of bronze. Forced draft gets you to 2450F in the crucible for bronze fast the correct temp for pouring bronze:cool: Quote Link to comment Share on other sites More sharing options...
saintjohnbarleycorn Posted May 21, 2009 Share Posted May 21, 2009 I melt aluminum wire on a regular wood fire all the time in a small lead pot, the kind the plumbers use. I am not sure if this is not a pure enough way for you to do it though, maybe the smoke and all ruins it? maybe for casting you might want more control? I just am pouring it into cans for now. I have a whole lot of aluminum wire. Quote Link to comment Share on other sites More sharing options...
Slysmith Posted May 25, 2009 Author Share Posted May 25, 2009 Bent, Let me ask this about forced draft. Your propane was about WHAT PSI coming out of the tank. If I read this when you say "forced draft" you are NOT just allowing a tiny hole to venturi in outside air, but you are actually forcing air into the mix WITH the propane and this is creating a hotter flame. Although this creates a temperature higher than anything I need, I am curious about this configuration. One NEEDS to force air into a propane burner and cannot expect a tiny hole to pull sufficient air from the outside? I am not interested in these extreme temperatures at all until I feel very comfortable with not only melting Al, but in pouring, greensand casting and eventually lost wax casting. When I was in college, I was around a fair bit of bronze casting, but did not have the class. My sculpture class was not quite at that level, so I didn't get to do my own casting, but I'm about as experienced as you can get without doing the casting. I wonder if you have any images of your fancier, higher temp, furnace and the setup you have used. I only thought a blower was really necessary for waste oil furnaces and when you used coal in a forge. Once I have a source of firebrick (they ARE about an hour away from me) I am interested in forging my own tools to handle my simple crucibles (steel pipe). St.John, I'm just trying to get comfortable with melting/casting and then at some point I'll even try some potassium chloride once I have a good mask and protective gear. Folks seem to mis-interpret my future desire to melt things like iron as something I'll be doing tomorrow. When you say "lead pot" don't you mean that small scoop that is iron or steel that is used to melt lead? You don't actually mean that you are melting aluminum IN a lead pot. Sorry if I am off on the terminology there. Anyway, thanks folks for adding info. The books that are the tried and true for metal casters is also very welcome. I do wish someone that is familiar with and has used and built the perlite / fireplace cement type refractory would chime in and offer opinions or personal pitfalls. I know those of you that melt iron poo-poo at the wimpy capacity of such a furnace, but really folks, I am just trying to melt aluminum as a path for greater things to come. Just cause I ask about a coupela, doesn't mean I'm gonna build one tomorrow... ------------------------------------------ Can anyone that truly knows what they are talking about offer advice on how I might avoid burning my eyeballs (via EM radiation). I know that folks that work glass use some form of ruby lenses, but is the danger the same from melting glass as it is for heated metals? What is the wavelength of light that is the problem for the eyes (is it infrared?) and how does one SEE clearly when pouring or looking at the metal? -please don't answer that one without really BEING an expert on the EM radiation hazards. I certainly am not. Quote Link to comment Share on other sites More sharing options...
Charlotte Posted May 25, 2009 Share Posted May 25, 2009 (edited) Don't use pearlite in a refactory that will be direct contact with the hot gases. it melts. Back up insulation is ok. Pieh Tool company sells forging glasses that are also used by glass workers. Edited May 25, 2009 by Charlotte PS Quote Link to comment Share on other sites More sharing options...
Slysmith Posted May 25, 2009 Author Share Posted May 25, 2009 Char, so if I form my furnace with the mix and then line the center with just fireplace cement, then I'll be OK? I have seen quite a few "slumped" furnace images and I guess that was pearlite that was in contact with the fire. --thank you, I was considering mixing and making today. I'll keep the pearlite out of direct contact. What did you mean by back up insulation? I don't have access to any rockwool or fancy insulation. Hmm... so give Pieh Tool company a try. Thanks a lot. Does anyone know what happens to eyes that are overexposed to the EM radiation of a forge or furnace? Quote Link to comment Share on other sites More sharing options...
Charlotte Posted May 25, 2009 Share Posted May 25, 2009 Perarlite can be used as backing. As long as the temp is below around 1500 behind the facing it will hold up and provide some insulation. The facing in this case needs to be sort of thick like 1 inch or so. You can burn your retina and ruin your cornea from the uv and infra red. The same problems that glass workers and welders face. You go blind! Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 25, 2009 Share Posted May 25, 2009 Have you looked through the burner Blueprints? A gun burner (blower driven) is often favored by people needing lots of heat, not because it's the only way to get it but because it's easier than making and tuning a naturally aspirated burner. The operator is in charge of the throttle so how hot your furnace gets is up to you . Perlite has melting temp of 2,000f and is of limited use in melters. You can of course make a multiple liner furnace but just buying and using a properly rated refractory is time and money ahead. I have not used a home made perlite refractory, it isn't suitable for my needs and for $50 I was able to build a far superior liner with insulation. When he said lead pot he was referring to a cast iron pot used to melt lead, sometimes referred to as a plumber's pot. Buy a pair of IR rated safety glasses, UV is not a factor. Frosty Quote Link to comment Share on other sites More sharing options...
Slysmith Posted May 26, 2009 Author Share Posted May 26, 2009 (edited) Ok well Frosty, now that you have brought up eye protection.... I'm going to hope folks will chime in here. I clearly want to protect my eyes and I do not want to let dangerous radiation in. NOW, I am considering also working glass at some point and clearly would need some Didymium glasses with protection in other wavelengths. I do not want to skimp at all, but I also want exactly what I need. I was thinking of getting THESE lenses for both looking at the interior of the furnace when needed and if I ever did lampworking with borasilicate glass. I really want to get this right the first time.Mosaics Unlimited Didymium Safety Glasses - Fusing Stained Glass Supplies I have been looking for several hours over many days trying to educate myself on the eye damage issue. Many folks say that unless I'm going to try and use borax to try and clean up the metal, then I don't really need to worry about sodium flare... OK but there are many other issues as well such as getting just too much visible light in your eyes as well. My wife has crappy night vision and mine seems to be superior to at least hers. I really don't want to screw that up. Found a good article on the whole issue with the EM radiation thing HERE:Visible Light Hazards and the Glassworker Edited May 26, 2009 by Slysmith Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 26, 2009 Share Posted May 26, 2009 I have a couple pair of dydimium glasses and they aren't very good for forging at all, only the slightest filtering of borax flare. Must not be any sodium in borax eh? You aren't going to get a definitive answer to your questions, too many variables mostly with your sight. The closest you're going to get is by consulting the welding industry. Better yet just buy a pair of #5 cutting and brazing shades and call it good for hot metal. These are good for staring into the puddle of molten steel while you weld, all - day - loooong. IR protection is whatever plastic/glass the glasses are made of. For casting you arent going to be standing there staring into the furnace or crucible so protection from dangerous debris is a much higher priority. For that I recommend a tinted face shield with clear safety glasses underneath. This gives you a double layer of protection if something goes south and you have molten metal in the air. This can happen very easily and it's all over but the screaming faster than you can blink. The tinted face shield will allow you to spend some time if necessary looking into the fire and protect your face as well as your eyes. The clear glasses will protect your eyes while allowing you unrestricted vision while you aren't staring into the fire. With or without shades your eyes will adjust to available light so if you're looking into the fire with tinted eye wear then look away you'll be half blind till they adjust. If however you can flip the face shield up and have clear glasses you're vision's good immediately and you won't be compromising your eye protection. For working glass the dydimium glasses are excellent. Unbelievable excellent in fact. Last I talked to Mike Porter he was working on filtering glasses for different uses. Dydimium filters sodium yellow and other coatings will filter other wavelengths. His goal was to come up with a coating or searies of coatings that would filter torch welding, forge, brazing, etc. glare without a dark tint. I haven't heard anything from him though so I don't imagine it's anything but an interesting possibility just yet. Frosty Quote Link to comment Share on other sites More sharing options...
Charlotte Posted May 26, 2009 Share Posted May 26, 2009 Gold reflective lenses are Ir reflective. Most welding gas suppliers carry a dark like number two or three green tint glasses that permit cutting torch work. Thes are often used around welding and cutting operations by the helpers so that they won't get accidentally dazzled. I used prescription saftey glasses with a number three welding tint for my forge and torch work. Get double strength polycarb prescription lenses with side shields and a face shield over that and you will be good for back yard casting im my opinion. But that is my opinion. Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 26, 2009 Share Posted May 26, 2009 I like the gold coated lenses when you can find them. They don't change the color, just dim it. #3 for cutting, brazing, etc.? I thought it was #5 but it's been quite a while since I picked up any. I bought a box of tinted face shield refills and a few pairs of tinted goggles and glasses at a going out of business sale a decade ago and still have lots. Frosty Quote Link to comment Share on other sites More sharing options...
Charlotte Posted May 26, 2009 Share Posted May 26, 2009 Actually at the momemt I don't have my prescription. It may have been five but then I didn't do much serious torch work. I think it was three. However the major point is that Welding suppliers have plastic, glass, and polycarbamate saftey glasses by the gross. Poly is by far the best and if gold tinted resists Ir. Poly is also uv absorbant so provides some help that way. Quote Link to comment Share on other sites More sharing options...
RcRacer Posted May 26, 2009 Share Posted May 26, 2009 I am not a professional blacksmith or a weldor but I did sleep at a Holiday Inn last night All kidding aside, when I took a course for TIG welding, the instructor indicated that polycarbonate safety glasses with ANSI ratings for UV/IR filtering will protect against UV/IR damage. The tint should be selected to suite your comfort level. I currently have shade 3 safety glasses that I use when plasma cutting and they are ANSI rated for 100% UV/IR protection. Shade 3 is about right for tint and comfort for me. Just make sure you are buying a reputable known brand name when buying safety glasses or goggles. YMMV PS. My welding helmet is auto darkening and has a grind mode. The lens remains at the lightest shade but still offers full protection. The hood doubles as face protection. It works great but is not always the best for full field of view capability. Quote Link to comment Share on other sites More sharing options...
Slysmith Posted May 28, 2009 Author Share Posted May 28, 2009 Guys that is great advice. Like someone said earlier about making a forge/furnace, you can't have one thing do all jobs safely. I think I am going to use something utterly different for glass and something else for metals. Now, I suspect that clear polycarbonate should be all that one EVER needs for IR light. It really just can't get through a thick layer of plastic as I understand it. That is why greenhouses work. Well perhaps SOME gets through, but most IR should be stopped with just a bit of thick plastic. Frosty, I was going to get by with a welders mask I have, but I think I'm going to go with a full face shield instead. Safety is just too important to let something not be protected on the face. I mean really... skimp on safety equipment... that is just stupid. A face shield with a pair of IR/UV wrap arounds sounds like the right set up. Now, as a science teacher, I have a lot of aprons, but they are really only good for something like hot exploding test tubes. I can't imagine molten metal not just pushing right through it. As I mentioned, a friend has a jacket that is used by the guys with the flashlights that direct airplanes and THAT comes with a warning that it insulates enough that you wouldn't notice the jacket as being on fire. That would be for my chest area with SOME apron over the front. Then I'm thinking welders gloves and for shoes, I was thinking hiking boots (that have laces). Now someone said you cannot have exposed laces no matter what, so I was thinking of making some kind of dorky leather cover over the parts of the boots that have laces. Any opinion on that folks? Feel free to chime in on safety. I'm planning on melting over sand/dirt in the back yard. Nothing but Al ingots at first. Tomorrow I am off, but taking care of my son. I expect that I may get the chance to take pictures of what I have so far and possibly post pics. Then in a day or two get started with the furnace. Though it may be boring to all of you helping a noob get up to speed, I really appreciate the expert help folks! Quote Link to comment Share on other sites More sharing options...
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