DIY Melting Kiln


Introduction: DIY Melting Kiln

This is an instructable on how to make your own mini kiln. Because I was able to find most of the materials in dumpsters at construction sites, this project only cost me 8$ in materials.

A kiln is a great backyard project to work on and is a very simple concept that will take only a few hours in labor.

With this kiln you can take anything from pop cans to old computer parts, motherboards, and cell phone parts to melt down and extract valuable metals from them. With pop cans you can create solid aluminum blocks, or you can pour the liquid metal into ant holes or pre-fab moulds to make anything you want.

You can also melt down glass and turn beer bottle into cool re-use projects such as serving platters and glasses. A quick Google search will show you some cool projects.


  • · 30kg of concrete (or if you are willing to spend some more money get high heat mortar)
  • · Propane tank
  • · 2” PVC pipe
  • · Stainless steel container
  • · Charcoal
  • · Sawsall (or grinder)

Step 1: Step 1 (Safety)

  • The first step of this project is ensuring that everything you are doing is safe. I have learned out the hard way that grinding metal and MRI machines do not go hand in hand. Also, if you are working with any type of compressed gas container, even though it may be empty, there is more than likely residual still inside.

Step 2: Step 2 (Cutting the Tank)

  • Before cutting the propane tank you will have to mark out a cut line. As seen in the photo below, I have drawn a cut line around the tank, approximately 4” down from the top.
  • IMPORTANT: Once the line is drawn we will need to prepare the tank and ensure all gas is released. I was able to remove the valve on top of the tank and fill it up with water. After swishing it around and draining it, I was confident that and fumes or gas was gone.
  • Using a sawsal or angle grinder cut along the line you placed around the tank. You might want some ear protection and safety glasses as this process is loud and messy. Also, stay away from any combustible materials as there will be lots of sparks.

Step 3: Step 3 (Preparing a Forced Air Intake)

  • To create hot fire within the kiln forced air (o2) is essential. At the bottom of the tank cut a 2” hole in the tank around 3” from the bottom. The 2” PVC pipe will be inserted into this hole which will provide air to the fire.
  • Since we have air entering the kiln, we will need an exit hole. Cut or drill a 2-3” hole at the top of the tank

Step 4: Step 4 (Creating the Concrete Wall)

  • A barrier between the melting pot and the steel tank wall will be required. The best way to do this is to clad the inside of the propane tank with concrete. For this step I did not have a cylinder small enough to allow for a wide enough concrete wall; so I used a cut log.....some redneck engineering
  • Before placing the log into the tank, you will need to pour some concrete in the bottom of the tank to create a solid base. Then place the log in the tank (center), fill in the sides, and smooth out.
  • Next, take the lid of the kiln and fill it in with the remaining concrete that you have. Place a peanut butter jar (or something comparable) in the center of the lid to ensure the exhaust hole is not covered.

Step 5: Step 5 (Curing Time)

  • Now that everything is poured let the cement cure for 24hours
  • After curing is complete, remove the log and the peanut butter jar to unveil the melting chamber

Step 6: Step 6 (Melting Process)

  • Place a base layer of charcoal pucks in the melting chamber
  • Place a stainless steel can or container on top of the charcoal base layer (filled with melting materials) and place additional charcoal pucks around the container. This will help ensure even heat distribution
  • Attach a shop vac (blower) or hair dryer to the PVC air inlet pipe
  • Heat/light a few of the charcoal pucks
  • Attach the kiln lid, turn on the blower, and watch the kiln heat up
  • If done right you will see an orange glow from the inside and the kiln will sound like an aircraft engine

Step 7: Step 7 (Final Results)

  • After around 10 minutes we were able to melt down 6 aluminum cans
  • Be careful when removing the melting container (CRAZY HOT!!)
  • Below the top layer (impurities such as paint and plastic) there will be pure aluminum

Be safe and enjoy melting anything you can :)



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    17 Discussions

    Surely a pvc pipe would melt?

    I know this is an old post, but about how thick should the concrete/heat mortar be on the inside of the tank, and does anyone know about how hot this might get using coal as fuel? Thanks.

    1 reply

    A lot hotter with coal! The concrete on mine was aroun 3-4"

    Y'all know concrete explodes in high temperatures, aye?

    4 replies

    A cheap heat refractory concrete can be made with a 1:1 ratio of plaster and sand. Both bags usually run about $6 at HD. I've been thinking about turning my old propane can into one of these...

    Can one suggest finding old worn out fire brick and using it - by smashing the bricks into smaller pieces and adding to the concrete mix (new) as an additive to ensure high heat and more insulating quality in the interior wall of the unit? Was thinking that might be possible ...

    Good thing we have the 1/8th thick steel container surrounding it :) just can't pour water on it. Then you will see it Crack.


    2 years ago

    yes - I have looked into Hang drums, an UNUSED brand new tank is what the pros recommend. (I'd do the same here, for safety's sake) They run $ 38.00 USD (new) at some hardware stores. That would be the most pricey aspect here other than the Sawz-all or concrete/mortar mix if one were to continue per Justin's instructions.

    At this point the one I have does not. This is mainly due to the fuel being used. in order to produce a high enough heat at do it quickly you will need to put lump coal in the kiln instead of charcoal. I am going to try running the kiln for a long period of time to see if the copper will budge.


    3 years ago

    What do u melt the cans in to make them into squares?

    1 reply

    I usually use stainless steel (or any thick gauge steel) containers or baking pans. The stainless steel will withstand much higher temps than aluminum and brass, therfore it will not melt when pouring the molten metal into it.

    Backyard metalcasting can be both fun and dangerous, anyone who ventures into this hobby would be well advised to heavily research the dangers before setting one up. Accidental spills on concrete can lead to explosive steam filled reactions with latent moisture, and is but one possible hazard. The advice given is not meant to diminish this fine Instructable, merely augment it, have fun but be safe.

    1 reply