"Cheap as chips".....homemade crucibles.....the story so far....

Discussion in 'Foundry tools and flasks' started by Jimmy Cogg, Oct 12, 2018.

  1. Jimmy Cogg

    Jimmy Cogg Silver


    Whoah Kelly!!! That is some really AWESOME furnace you have built.

    I'm just using "bellows and charcoal" technology and you're at Star Wars light sabre level!

    For the crucibles I make, yes, when green, they are delicate and have some plasticity. They are 50% damp clay and even when rammed and compacted, on demolding, they are slightly plastic. When dried they take on a very weak hardness and can be handled more easily. At that point I could grind them up again and remake them if I wasn't happy with them. They only, chemically change and have true strength when fired in the furnace, or kiln if you have one.

    I am interested in mechanical vibration and compaction. I have a few ideas. I do want to make some bigger crucibles, so I'll redesign my mold and try a more mechanical compaction, maybe an air hammer attachment, or something like that and I would go with an even drier mix with something like that.

    Regards,

    Jim
     
  2. Jimmy Cogg

    Jimmy Cogg Silver

    Hi Jeff,

    It was you and it wasn't a video.

    I've checked and was reading your commentary on your furnace build and what you had done.

    Your description must have been "painting pictures" in my head!!!.....or created that "video" I have mistaken it for. Cheers anyway. I like the idea a lot.

    Jim
     
  3. Jimmy Cogg

    Jimmy Cogg Silver

    Right, crucible upgrade :-D. I'm going to try this mechanical vibration and compaction idea that you've given me. I think it will be a vast improvement on what I've been doing.

    New Crucible pattern.jpg

    I have redesigned my crucible for this and now made the pattern in plaster of paris. It is approx just shy of A16 size, 3 litres brimful capacity. I'm going to encase the pattern in concrete to create a mold and then make one or two up. I have good hopes for this. If it works I can extend the mold, with a additional ring and insert, to create a higher capacity crucible may be to A20 size.
     
    Mark's castings likes this.
  4. Jimmy Cogg

    Jimmy Cogg Silver

    A16 size plaster of paris crucible pattern now encased in curing concrete.....can't wait to demold it :D

    A 16 crucible mold in concrete now curing.jpg
     
  5. Jimmy Cogg

    Jimmy Cogg Silver



    The raw concrete mold is now cured and demolded. Preparing it for pressing a clay/grog A16 sized crucible.

    I think that I have enough bottom space to add a spacer to the insert and upgrade the crucible to a slightly larger size......I want to knock a few of these out fire and glaze them up....then test for longevity.
     
    Tobho Mott and Mark's castings like this.
  6. Jimmy Cogg

    Jimmy Cogg Silver

    Right the next (un) 'exciting' installment. Molding up the crucible. I tried this first using powdered graphite as a mold "lubricant" or parting powder......it didn't release properly so I reused the grog/clay this second time using petroleum jelly and cooking oil as a release agent. It worked well.



    Just need to put it for a few days in the drying cabinet and dry the clay out slowly before first firing. I've purchased a high temperature commercial potters glaze and I'm going to give that a whirl once the crucible has been fired.....assuming it doesn't crack or show serious flaws in the drying process!!!
     
  7. PatJ

    PatJ Silver

    I would not attempt to make my own crucibles, but I admire someone who has the desire and tenacity to figure out how to do that.
    No doubt a quality crucible could be made in the home-shop environment given the right materials and process.
    Its an interesting video.
    Seems like I have seen some videos online of how commercial crucibles are made, or perhaps it was just printed material.

    Good luck with this.
    I hope you get it figured out.

    .
     
    Jimmy Cogg likes this.
  8. Jimmy Cogg

    Jimmy Cogg Silver

    Thanks PatJ. It's just a puzzle waiting to be cracked......or may'be that will be the crucible.

    All good fun, making something out of nothing. Cheers.
     
  9. Al2O3

    Al2O3 Administrator Staff Member Banner Member

  10. Jimmy Cogg

    Jimmy Cogg Silver

    Thanks Kelly, that is very interesting. He is following exactly the same path as me with the same book. I should be able to swap notes with him. I'm just about ready to fire my A16 size, as it looks like it has dried out in the airing cupboard, together with 3 smaller ones, so looking forward to that.

    I am liking the mechanical rib idea with the rotating mold on that Morgan crucible video. I think that has legs and I could reproduce that to produce a better product more efficiently. I'm mulling it over at the moment and will make a decision whether to go that route on the outcome of the current A16 project.

    I've also invested in John Campbells Complete Casting handbook, so I've got a lot of bedtime reading to do!!!

    Cheers! Jim
     

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