Project Crucible - Making a Crucible for the Aluminium Smelter

Small Propane Tank Crucible (No Weld)

     So I had made a decent propane tank based, coal fired smelter for melting aluminium, for pouring into ingots and casts.

     You can view the making of the Smelter here Propane Tank Aluminium Smelter (No Weld) and I also made some tools to with it that you can view here Tools For Smelter (No Weld).

     Now all I needed was a crucible, so that I could begin to melt down all of the lovely aluminium that I had been hoarding.

The Project Starts

     I had purchased a two pack of Coleman small propane tanks (it was just as cheap to buy two as it was for one), and seeing as I have an attachment to fill a tank from a larger tank, I was left with an empty that seemed to be a suitable option for this project.

     The first thing that I did was to inspect the vessel and wipe it down, this gave me time to think about how I was going to proceed with the project.

Some Health and Safety

     Firstly some health and safety warnings: Propane under pressure is dangerous and there is a rick of fire and explosion if not dealt with in a safe manner. So it is important to ensure that precautions are taken before producing any sparks while drilling or cutting, to ensure the gas is removed and do all that you can to prevent any risks of explosion or fire. Do not smoke while undertaking the process of prepping the tank or while cutting into it.

     There may also be residue inside the tank, clinging to the sides of the inner walls that could possibly still be flammable even after opening it, so be cautious and take care. Remember that it is hazardous material and treat it with respect and caution.

     Also remember that propane is bad for the environment when released directly so try and limit that by using it first for its intended purpose to limit the contamination. In other words use the gas and try to ensure the tank is completely empty.

Stay safe in all of your projects, remember if you get hurt, you wont be bale to create things.

First Things First

     So onward, as I then had to ensure that the tank was completely empty, so I left the nozzle on overnight and in an open position to make sure that it was completely empty.

     On the side is a small pressure valve, that with some skill you can actually get out, I did not bother doing that, but I did stick a small rod into the valve to release the pressure and also left that in all night.

     The next day I was sure that the tank was empty and ready to progress with the next stage, seeing as it was a small tank I was confident that it was empty. I did not flush this tank like I did with the big one, but I did decide to do it all by hand and not use anything that could spark.

Deciding Where to Cut

     I used some green tape to cover around the top section and then measured out just how deep I wanted the crucible to sit in the smelter.

     I made sure that it was not too tall so that the lid would close, but yet had enough room for coals to be placed under during the initial fir up.

     I then marked around as straight as I could to give an even cut at the desired position.

Preparing The Cut

     I then positioned the small tank between two pieces of wood that I roughly secured to the bench, this was so that it would not roll around while I was cutting and gave me more control.

     I used a fine tooth metal hacksaw and began to work one area first, slowly and with caution just in case there was still gas inside.

     When I was happy that it was safe, I then went around the entire thing, slowly to score where I wanted the cut and the continued to cut through the entire thing.

Cut and Open

     Now the top came off nice and relatively even, so I was happy, it was also clean although there was still a strong smell present in the vessel.

     I discarded the top section into the scrap pile and peeled off the tape ready for clean up.

Clean Up

     I then took a fine file and went around the top lip to ensure that there were no sharp edges or loose pieces that could stick in my hands. Although I was wearing safety gloves, I did not fancy getting a metal splinter latter on.

     I then washed it inside and out thoroughly with decent liquid and dried it completely.

     A tip is to make sure that you do not go and use the scrubby being used for dishes and also make sure that you clean up after yourself, or you will be at risk of being told off especially if you do clean it in a just cleaned kitchen.

A Heat Up For The Lip

     At this point I had considered actually using a wire brush or wheel to remove all of the paint from the outside of the tank. But I decided that it would be just as easy to burn it all off when I first used it in the smelter.

     I wanted to make a pouring lip, so that the melted aluminium would flow when poured and have more control.

     I used my propane torch to heat the area that I had selected, it lined up front to the base hole where I would be using a hook type rod to help pour.

     On Coleman tanks, there is a section at the base with holes in, it is attached securely but not part of the sealed tank. The idea is if you set it in water it will drain out preventing rust I guess. I left that on because then the heat would get under the actual crucible without the need to try and add coals under it.

The Lip is Formed

     Using a method of heating up the area and while wearing decent heat protective gloves, hammering a lip using a ball Pein hammer as the lip began to form.

     I then quenched the vessel in cold water and gave it a wipe over as I inspected it.

     At this point Ii was happy with the way the project was going.

Adding Some Handles

     Now my original idea was to use some form of tongs to pick it up, but I was concerned that it may slip while loaded with molten aluminium.

     Then I considered drilling holes and using tongs with bolts in, but during my play around, I ended up with a two rod either side with hook end tool that would enable me to pick the vessel up easier.

     So I drilled the holes and inserted some good industrial bolts that I had stored away and tightened them with locking washers and nuts.

Testing the Pick Up Tool

     Now that I had the bolts secure, I had to test, to be sure that the tool I had made to pick up worked. So I sat the crucible on the bench and used the tool to pick it up. 

     I was happy that I did not need to bend the rods inwards to make it fit and pick up the vessel. So I was now more confident that it would actually work,

Tilting The Vessel

     I was a little concerned that the vessel may come out of the hooks when tilted.

     So I played around and it seemed to work smoothly without any adjustments being made

Hooking The Vessel

     I also wanted to make sure that I was able to pour using the one handed pickup tool and a hook rod that I had made.

     I figured that it would possibly be clumsy, but when I picked it up and poked the rod hook into the base it was actually quite a smooth operation.

Initial Fill

      I have a huge mass of collected aluminium compiled of different types and thicknesses, so I filled up the crucible so that it was packed.

     I knew that even though it was full the metal would melt down to a small amount, but provide a base of hot molten aluminium base so that I can feed more through the top of the smelter.

Ready To Fire

     So I positioned the filled crucible into the smelter and surrounded it with coals, I packed enough to keep it secure but also enough to ensure it was easy to light using a propane torch and I was ready to go.

Rapid Melting

     At this stage I did not have time to take pictures, it seriously started to melt at a crazy speed. The crucible became real hot, and the aluminium melted fast, so fast that I was struggling to feed it quick enough. Also I was eager to get at the skimming off and pouring of shinny molten aluminium.

     I had to add more charcoal now and then to maintain a decent temperature and melting steady.

     But it was eating up what I fed it and I was both amazed and joyed at how effective it was all going.

     Every now and then I scraped off the dirty slag from the top and got a glimpse of molten shiny goodness and all was going to plan.

     I could not wait to pour it all into pans and produce lovely ingots of recycled materials.


     As you can see from the picture, it all went to hell, as the crucible failed. Well actually the crucible did not fail, I did, you see as the crucible was red hot, the walls were good but could easily be punctured with force.

     In my eagerness to melt it all, get that shinny aluminium, I dropped a rather chunky and long piece that you can see has not melted, into the crucible. I then tried to push it down and well I punctured the bottom of the crucible.

     The tip is, leave it, let it all melt on its own, do not try and force it to melt faster by pushing and packing too much.

     So as I was feeding it, all of a sudden the crucible half emptied, I was horrified as I knew that I had messed up big time.

     I tried to remove the crucible but it was impossible, you see although the melted aluminium did not come out of the smelter. The air blower had cooled the melted aluminium and fused it with the coals and the base and sides of the smelter lining.

     My only option was to leave it, I turned it upside down on a dry dirt area and left it to cool.

     I then later, smashed out the crucible, now because of my over eager mistake, I have to smash out the lining and repair that and make a new crucible.

Final Thoughts and Notes

     So, I think that if I had not punctured the crucible, it would have all worked out and I would have produced some decent ingots.

     Even though I never expected the crucible to last forever and expected to make a new one after at least a few times of use, I did not expect to puncture the bottom, lesson learned.

     I intend to make another crucible in the same way as I want to test to see if it all would have worked out.

     This time I will get pictures and video of the feeding and melting process and hopefully pouring.

     I am also going to look for other vessel ideas and solutions, one is to use an empty car extinguisher as the walls are thicker but I have yet to find one.

     Another idea is to use a thick steel wide pipe section and have someone weld a plate to the base.

     I will play around with making my own crucible as I do not want to have to pay out for an expensive graphite crucible.

     One day if I make a smelter using electric or gas, that melts more than just aluminium, I will possibly invest in a decent graphite crucible.

Additional Information

     I have finished repairing the smelter and emptied the other Coleman tank.

     I have also made a heat table to place the crucible on should I need to along with the tools that get rather hot.

     Once all is ready I will on a decent day, fire up and take another crack at melting the stocked up aluminium.

Tag Random Nph
Lemons are sour.

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