I typically am melting small 1-2 ounce melts of scrap silver and gold at a time. My Meco does a good job of melting silver and gold. I have started to work a bit in brass and am generating a fair amount of scrap. I also find myself needing shapes that I can only get from pouring odd shaped brass ingots. My meco on propane and an O2 concentrator doesn’t produce enough heat to melt brass in an open crucible. I don’t want to go back to regulated propane and O2 cylinders. I bought and tried a Devil Forge propane melting furnace and it will definitely melt brass, but it is very difficult to keep the brass melted in small amounts while I transition to the ingot mold. I sold the furnace yesterday to a guy who has no idea what he will use it for, but wants it. I thought that my good old trust prestolite acetylene torch would do the trick, so I fired it up and it didn’t, even with making a firebrick tent. So my question is, will an electric melting furnace work for me in the small amounts of silver and gold that I cast and will it be able to melt brass? I am looking for general answers to these questions and recommendations for what electric furnace to buy. Any help is appreciated…Rob

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Rob,
I’ve used the Kerr version of this electric furnace for many years. Sadly, as it says in this description that Kerr discontinued their jewelry product line in . This model is supposedly the same as the Kerr version.

I know there are other electromelt furnaces out there, but I’ve never used them.

This will definitely melt gold and silver and will melt brass, but remember that brass is a mixture of copper, tin and zinc. As you have probably learned (for lack of a better way of describing it), brass is a dirty metal to melt. The zinc burns off, creates toxic zinc fumes and will coat the inside of your electric melting furnace with burnt zinc dust. You’ll have to clean out the melting furnace after every time that you melt brass otherwise it will contaminate your silver and gold.

I’ve melted lots of brass throughout my lifetime and these days I strive to never melt it. (I use silicon bronze for casting.)

Hope that helps!!

Jeff

Rob, I use the kind of furnace with a removable cylindrical crucible.

Yes you can pour small quantities with it as long as you do it quickly. The last bit out does tend to ‘solidify’ into a kind of slush if the pour is a bit too slow.

Recently I read somewhere, here? of using a torch while pouring the furnace crucible. I haven’t tried that, haven’t needed to, but can see that it would work, make it less important to rush a pour.

I dedicate one crucible per metal type. Argentium, standard sterling silver, Rio’s ancient bronze. Works out well.

The crucibles I’ve bought have a too-small spout in my opinion. Using a round rasp I’ve filed it deeper into the crucible so the melt gets lined up and narrowed down sooner.

Some time ago an Orchid member mentioned weighing new graphite crucibles and checking their weight after each use to help determine when they may be getting too thin.

Neil A

Yes, you’re correct. The molten brass won’t destroy the electric melting furnace. You’ll just have to clean it each time and keep a separate crucible for each metal.

We just had a thread about pouring ingots. One of the things mentioned is being fast & efficient. You’ll just need to practice a bit. I’d recommend heating the metal a bit hotter than usual. F -F. Once you get your technique down, you shouldn’t have any problems pouring 2 oz of silver.

Like Neil A says, some folks like to keep a torch on the metal as you pour to eliminate oxidation between the taking the crucible out of the melting furnace and pouring into the ingot mold. This torch doesn’t have to be a high temp casting torch. The metal is already molten. You’re just burning away the oxygen. I think you said that you have an EZ/Orca torch. That should work fine.

I have used those cylindrical furnaces before and not only do they ALWAYS fail, they are difficult to service and require the use of expensive rimmed+grooved graphite crucibles.

I have since started using front-door electric kilns with great success. I require my kilns to go up to °F (°C) and these are the only affordable options that aren’t induction. I’ve had the best success with vintage kilns as, in my experience, they were made with kanthal wire which can take the heat required for brass and bronze. The newer, cheap nichrome elements won’t last.

They allow you to use any type of crucible you want. For precious I go with a ceramic sleeve and graphite crucible+lid. For brass and bronze I use a clay-graphite cup crucible. My bronze melting kiln is a Paragon from the 70s. The only downside is they can take a while to heat up. I have melted 2lb of bronze before without problems.

I’ll through in my 2¢…

I purchased this furnace:

The furnace heats up very fast. The only issue is the company is not a company i would do business with again. I’ve had to rebuild it a few times due to less than stellar quality control and they overcharge heavily for replacement parts.

It is a simple design though if someone wanted to make one themselves. (And had a lot of time to burn)

The Tabletop company has only been around for a few years. Looks like they got you with their name. He’s not referring to furnaces that sit on a desk, but the brand name “Tabletop”.

Newer kilns either use Nichrome elements, which burn out at high temperatures and firing intervals, or go too thin on the gauge. It also becomes brittle after firing and can snap and short out. Better kilns will use thick Kanthal elements which last a very long time and are easy to service. Vintage kilns were overengineered.

Nowadays kanthal kilns are catageorized as “high temperature” furnaces and carry a steep premium, for whatever reason. Kanthal is only a bit more expensive.

Since my last post, I have done a lot of research (wasted a lot of time on the internet), regarding small electric melting furnaces. Other than variations in size, capacity, quality and price, the main variable that I have yet to resolve is furnaces where you remove the crucible with tongs from the furnace and pour the melted metal vs pouring melted metal out of the crucible by tipping the entire furnace as in the old Kerr design. I would be interested in comments regarding both designs. Thanks…Rob

The only electric furnace that I’ve ever used is an older Kerr removable crucible version. It took me a little bit of practice to “dance” with it because if you’re vacuum casting or casting an ingot there are number of components to coordinate, pretty much all at once.

For me, making a comprehensive plan of every step and then going through the motions, practicing with all of the parts while they were totally cold was very helpful. My goal was to create intuitive muscle memory, so when everything was hot & ready my hands knew what to to do without thinking too much. Once I did all of that it was pretty easy to make it work.

Besides all that, the best advice that I could give is to make sure that you have tongs that are easy to work and fit your crucible securely.

I’ve mentioned this before, but most jewelry tool companies have a 30 return policy, if you want to buy an electro melt furnace and try it. From your description it sounds like you’ve done a pile of research. Is there an easy way that you can get your hands on an electro melt furnace to try? A jewelry school, jewelry tool company, friends with jewelry stores within driving distance? Like I said, for me it took a bit of time to practice.

Let’s see what others say.

Good luck figuring it out Rob!

Jeff

Dual Fuel Metal Melting Furnace

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Introduction: Dual Fuel Metal Melting Furnace

About: I have a compulsion to make stuff, all kinds of stuff. I'm glad to be here... More About spike » I got such a great response from the Easy Dual Fuel Furnace Burner that it only made sense to follow it up with the rest of the furnace.

This furnace will be able to handle melting aluminum and bronze with no trouble. In theory it should be able to melt iron too but that's probably pushing it.

I've been using my furnace for a couple years now and it has worked out quite well. My design is based on information I picked up from the backyard metalcasting forum. It's a great resource and community. There are a bunch of furnace builds there exploring a variety of ideas. I recommend checking it out. I'd also read thiscomprehensive guide for a general overview of metal casting and furnace design.

Step 1: General Plan

The basic concept is that we are making an insulated container that can withstand temperatures of up to degrees. The dimensions don't need to be precise but you will have better results if you stick with the general program. I wanted a furnace that would let me cast a decent amount of metal, about 5 lbs aluminum.  It needs to be sturdy but as inexpensive as possible to make and run.

The furnace is really simple. It's just a metal container with a lid, a drain and a hole for the burner. It is filled with high temperature insulation to retain the heat and a sturdy inner lining (hot face) to withstand the flame from the burner.

I based my design around a small metal barrel that I got from a salvage place. The sheet metal was thick enough to weld to (pretty much) and not galvanized. The zinc coating on galvanazed metal containers will burn and make a noxious smoke so don't use it. Otherwise any metal container should make a serviceable shell for the furnace. I used bits of pipe and angle iron from my scrap pile for the rest of the metal parts.

I made my own insulation because it was substantially cheaper than buying commercial insulation and I just wanted to try it. I did buy a bag of high temperature refractory cement for the hot face.

The shell is filled with insulation leaving an airspace of roughly 2" on all sides between the crucible and the inside of the furnace.

Step 2: Dimensions

My barrel for the outer shell is is 17" high x 14" dia. I cut the top 3.5" off the barrel for the lid. The shell is filled with 2.5" of insulation and an additional 1/2" of hot face for 3" total. I filled the floor a little deeper- 4.5" of insulation and 1/2" hot face. This left an inside cavity of 9.5" high X 8"dia. There is a 4.5" hole in the top to let the exhaust out and to access the crucible for feeding it metal.

Step 3: Mix the Insulation

I wish I could say that I thought of starting with mixing the insulation ahead of time when I did my build. You can benefit from my experience and start it first.

The insulation needs to:

Be strong enough to withstand some banging around

Not melt at high temperatures, it should withstand degrees F at least

Insulating enough to retain heat

After hunting around the internet I came across a low-tech method to make fire bricks. It was a mixture of fire clay and sawdust. When it is fired for the first time the clay hardens and the sawdust burns out leaving little air pockets.  You are left with a lightweight insulating product that just laughs at extreme temperatures.  

The fire clay is a very high temperature ceramic that comes in a powder form. You can get it at pottery supply stores. I got a 50 lb bag of Hawthorn fire clay for $20. I used about 1/2 of the bag for my project.  Make sure to ask about the temperature rating of the clay.  You want something that won't break down at high temperatures.  Do not use Portland cement (the stuff concrete is made with) for your binder; it can't take the heat and will just break down over a few uses.

I used shavings from a planer for my filler because they were fluffier than regular sawdust.  You can get it from free from any commercial woodshop.

Recipe

All of the measurements are by volume.  

I used a big coffee can to measure with and a large plastic storage container to mix in.

First make a dry mix of 3 parts sawdust and one part fire clay

Mix it well until the clay is well distributed with the sawdust.

Add one part water to the dry mix

Mix well again

Let the mixture sit at least 12 hrs.  

This allows the water to fully hydrate the clay.  You will be able to tell the difference once it is ready. The mixture will be less sticky on your hands and form a nice ball easily.

While you are waiting for the insulation to hydrate you can start on making the forms for casting.

Step 4: The Lid

The first step is to cut the top off the barrel for the lid.   I used a grinder with a cutoff wheel to slice off the top 3.5" of the barrel.  File or sand the ground edges so they aren't sharp after you are done.  

Take the piece you just cut off and place it upside down on a board covered with a sheet of plastic.  The side facing up will be the side that faces the inside of the furnace. Make a cylindrical form for the vent.  This needs to be 1" dia larger than the final hole.  In my case I wanted a 4.5" vent so my form needed to be 5.5"  I like to wrap my forms in plastic so that they are easy to remove after the castable is dry.  I used a dog food bag (a little tougher and stiffer than plastic sheeting) for this project and it worked great.  

Cut some remesh wire or something similar, preferably not galvanized, to support the insulation.  Weld it to the lid.  Weld a couple tabs with holes drilled in them too.  We'll use these to hang the lid later.

Fill the lid with insulation leaving a 1/2" space at the top for the hot face cement.  I forgot and had to scrape it out later as well as widen the vent.  No worries, it all worked out.

Set the lid somewhere warm to dry.  This will take a while.  Plan on a week to ten days or more. There is no chemical reaction going on here, the fire clay is just drying out.  Cover it lightly with plastic if it starts to get a dry skin.  Wait until it is firm to the touch, it can be a little pliable but not squishy before you add the next layer to it. 

Step 5: The Body

The body is a little trickier to mold but nothing that we can't handle.  There are three components that we need to consider when making the mold: the inside cavity, the tuyere (hole for the burner tube), and the drain.

The inner cavity is straight forward just make a form that is 1" dia wider than the final cavity size.  I cut a couple pieces of 1" thick styrofoam into 9" circles and wrapped them with sheet metal to make a cylinder.  Use duct tape to hold it all together.  Make a sleeve of plastic or dog food bag that fits snuggly around the form.

The tuyere is formed by a cylinder that comes into the furnace tangentially to the inner cavity.  This allows the flame to swirl around the bottom of the crucible rather than just blast it at one spot.  Place the inner cavity form into the furnace and inset the tuyere tube to mark it for cutting.  It enters the shell a little higher than the finished height of the bottom of the furnace.  Ideally the tuyere form also needs to be a little wider than the finished burner so that it can get packed with the hot face cement.  Don't forget to wrap it with plastic.  Weld a piece of pipe to the outside of the shell to support the burner.

 I had a 5" finished floor height so the bottom of the tuyere hole was set at 5.5"  The tube I used for the form was just a little bigger than the burner tube because that's what I had on hand.

Originally I was going to use a vertical drain but later opted for a horizontal one.  When you are melting down metal parts from the junkyard to make ingots it's nice to just remove the crucible and let the molten metal run out of the furnace into an ingot mold.  A horizontal drain makes it a lot easier to do that.  

I used a piece of 2.5" dia pipe and cut it at a 45 degree angle three inches from the end.  I cut a hole in the shell and welded the drain on.  The bottom of the hole for the drain should be a little below the finished floor level so that it will, well....drain.   This tube is oriented perpendicular to the inner cavity.  Looking down at the top of the furnace if the tuyere is entering at 12:00 the drain will be at 9:00.

Once all the form parts have been test fit remove them and fill the bottom of the shell with insulation until it is 1/2" lower than the finished floor height.  insert the form parts and carefully pack insulation around them.  Fill the furnace with insulation until it is 1/2" from the top. Use a stick to pack the insulation firmly as you fill the walls.

Let the furnace dry for a week and then carefully remove the forms if the insulation feels ready.  If there are voids or things crumble a little when you are removing the forms just pack a little wet insulation where you need it and sculpt it to fit.  It's very accommodating to work with.  Continue to let it dry, lightly covered if necessary, until it is firm to the touch.  

Step 6: Other Bits

While you're at it, cast some plinths and an exhaust cover or two from the insulation mix.  The plinth is a little puck that goes under the crucible and I bet you can guess where the exhaust cover goes. :)  Make sure to make it bigger than the vent...

Step 7: The Hot Face

The hot face is the inner liner of the furnace.  It is made from a specially formulated refractory (high temp, degree) cement.  The upside of refractory cement is that it is super hard, resists breaking down and doesn't usually shrink or crack as it dries.  In other words it's good at it's job.  The downside is that it can be hard to source and is pretty expensive- around $90-$100 a bag.  You shouldn't need more than a bag to line your furnace.  Ceramic supply houses, industrial suppliers or furnace repair guys are good places to look.  

If a hundred bucks is a bit hard to swallow there are a couple workarounds I can think of.  There is a high temperature mortar used for building and repairing fireplaces.  It usually comes premixed in a can and can be troweled or brushed on to a surface.  It can be found in hardware stores.  Make sure it's high temp.  It should give you a decent surface and not cost so much.  The other route is to just say forget it I'm not lining this thing.  It will wear down a little faster but will still work fine.  If you go this route just forget the whole 1/2" bigger stuff when you are casting and fill everything to the top.

If you decide to go with the high temp cement (Why not? I only want to build this thing once...) Be careful when you mix it.  It goes from too dry to too wet very quickly and a soupy mix won't fly here.  You want it wet enough that it is not crumbly but firm enough that you can trowel it onto a vertical wall and it will stick and not sag.  Apply a half inch of cement inside the the vent and on top of the lid.  I made a smaller form and packed cement between it and the insulation and then troweled more on the top.

Same with the body of the furnace.   Pack it on with your hand and smooth it.  Line the drain and tuyere too.

The cement should be pretty darn hard in 24 hours.

Step 8: Drying

Since we used a clay and sawdust mixture for the insulation there is still going to be a considerable amount of moisture contained in it even when it appears dry.  You need to drive out as much of this moisture as you can before bringing the furnace up to high temperatures.  I was worried about steam being trapped in between the hot face and the shell so I drilled several holes in the top of body with a masonry drill and then some in in the metal shell.  In retrospect I think I went overboard.  Four holes in the top and half a dozen in the shell would have been fine.  

To speed up the drying process I stuck a 100 watt light bulb (remember those?) inside the furnace, laid the lid on top and left it going for a couple days wrapped and covered with fiberglass insulation.  As it warmed up it steamed like a crock pot.  Once it was done steaming I pulled out the bulb.  The insulation in my lid shrank and cracked slightly but the cement held everything together.

Step 9: Attach the Lid

Now we need to attach the lid to the furnace.  I made a simple hinge out of pipe that lets me swing the lid in either direction.  The lid has two tabs welded to it that stick up from the top edge.  These are bolted to the V shaped frame which is welded to a piece of pipe that slips into a larger piece of pipe welded to the back of the shell. I had to weld an additional piece of plate to the shell in order to reinforce it and get the spacing right.  Adjust the lid so it sits 1/4" or so above the body of the furnace.  You don't want them to drag on each other.  Getting the lid hinge right is a little fiddly.  Take your time and get it right.  You don't want problems when it's super hot.

I attached a couple wheels on the bottom and a leg in the front too.

Step 10: Accessories

A furnace that gets really hot is nice but without the right accessories it's kind of useless.  You are going to need to make a crucible, some tongs and a hook for the crucible, a paddle/scoop for cleaning the molten metal, some more tongs for grabbing hot stuff and an ingot mold to get started.  A good time to work on this stuff is the week or two while you're waiting for the insulation to dry.

Crucible - I used a piece of pipe from the junkyard.  It's 4 1/2" in dia and cut to 6" high.  I used a piece of 1/4" plate for the bottom.  Cut it out in a circle and weld it to the bottom.  Make sure you did a good job welding the bottom on.  You don't want molten metal dribbling out.  I figure water tight is a good test.   There are a variety of ways to lift the crucible out of the furnace and pour it.  I went with putting a pair of lugs on the top and a loop in the back because it seemed the most secure to me.  They are made from a couple bolts and a nut I had in the shop.  Weld them on securely.  

Tongs, hook and scoop- I used metal that was in the shop and bent it to shape.  I used washers for the bottom of the tongs.  You could bend circles if you were inclined.  Make sure they fit over the lugs on the top of the crucible.  The hook is just a piece of 1/2" bar bent at the end for tilting the crucible.  The scoop is rebar and a piece of sheet metal.  The scoop part is 3" wide and bent up at the end to pull out crud from the top of the molten metal.

Extra Tongs- I got a pair of blacksmith tongs and they are really handy for moving hot stuff around.  You can make do with a big pair of slip joint pliers but it 's gonna be hot.  

Ingot mold- Mine is a piece of large angle iron with some plate steel welded on either end.  You can go as simple as a muffin tin but it's going to warp and twist over time.

Step 11: Firing

The first firing of the furnace is a crucial one. You are firing all the refractory materials and turning them into ceramics. It is important to bring them up to temperature sloooowly. Some people recommend a heat lamp first to start the heating process. I think that's a bit cautious. 

Put the plinths and exhaust cover into the furnace. 

Insert the burner and attach the propane and fan to it. 

Turn on the fan but choke it down until almost nothing is coming out. 

Light a torch and put it in the furnace. 

Turn on the propane until it lights.

Remove the torch.

I start with a very gentle flame just barely licking out of the end of the burner. Let the very low flame heat up the furnace for an hour. This should drive a lot of the moisture out. If after an hour there is no steam escaping from the furnace go ahead and turn the burner up some. Not a lot, just a little, wait another hour. Turn it to "medium" and wait another hour. Finally, crank it. As the furnace heats up especially the first couple times it will smoke as the sawdust burns out of the insulation. It will stop after a few uses. Depending on the power of your burner the furnace should start to glow anywhere from a dull red to bright yellow. 

Success?

Awesome!Good job! 

Turn off the furnace, Let it cool down and take out the plinths and exhaust cover. They should be light weight, yellowish and generally look like soft fire brick. If they fired well then you can assume the rest of the furnace did too.

Use a plinth under the crucible and the cover on top of the vent to adjust the furnace. You can choke it down some but never cover the top all together. The furnace needs to breathe.

Over time you will learn how to adjust the furnace and tune the burner by ear. 

Last Safety Talk

Melting metal at home is awesome. No doubt about it.

Going to the hospital......not so awesome.

Here's some cliff notes for being safe with molten metal:

Molten metal will burn you faster than you can react to it.

Leather boots are a must. Smart people wear gloves and safety glasses too.

Molten metal can superheat a little bit of water and spatter.

Preheat any metal to be melted, ingot molds and tools before getting them in contact with molten metal.

Don't drip metal onto damp surfaces especially concrete or stone.

Melting metal or burning out molds can produce poisonous gasses.

Make sure you are in a well ventilated area preferably outside.

Wear a respirator with the correct cartridges if you are creating a lot of smoke.

Metal furnaces are a combustion source.

Don't use the furnace in a closed room. You can asphixiate.

Prep your work area and keep combustibles away from where you are working.

Silica dust from sand can be a hazard.

If you work with sand molds wear a respirator or at least a dust mask when working with the sand. It's the tiny particles that you can't see that can accumulate in your lungs and cause silicosis over time.

This list is not exhaustive. Use the precautions that you feel are appropriate.

If you have any trouble following the instructions or need more explanation please let me know in the comments.

If you build a furnace post pictures in the comments so we can check it out.

Interested in what we're up to lately? Updates happen pretty frequently on Instagram and YouTube.

Thanks!!!

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