Tempering and Cleaning Crucibles

Discussion in 'General foundry chat' started by Darrow of Lykos, Jan 22, 2025.

  1. What are everyone's suggestions on best methods of doing these things? Also when do you use flux? I've seen it in multiple videos during people's melts.
     
  2. Tops

    Tops Silver

    I bring mine up to a dull orange slowly and cool back down before melting aluminum. I don't use flux. So far it's just been the Amazon specials, have not had the privilege of a Morgan. The one I have attempted bronze melts in looks worse for wear on the outisde. The one I use for aluminum seems to be in good condition.
     
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  3. I am only really looking at doing Aluminum, Copper and Brass occasionally. I have the crucibles that came with my kit that are definitely not Morgans. Which I just watched a video on their manufacturing process and damn those things look glorious. The thing that makes me nervous is the horror stories I've heard with these Amazon jobs that crack or blow out in the furnace in the middle of a melt.
     
  4. Petee716

    Petee716 Gold Banner Member

    I buy all of my crucibles from Legend in Sparks, Nevada
    https://www.lmine.com/product-categ...graphite-crucibles/budget-graphite-crucibles/
    The link is to "budget" crucibles which are fine for aluminum. They last a good long time for the occasional melter. But for copper alloys, the Salamander Super is a better option and is what I have moved on to, even for aluminum. Prices aren't terrible and they give good size information as well as break-in instructions.
    Crucibles are consumables. Some just get consumed more gracefully than others.
    Pete
     
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  5. @Petee716 thank you for the info sir! Where do you buy your Salamander Super's?
     
  6. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    I do the same with clay graphite crucibles of any brand, also before that first heat I put mine in a kitchen oven for a couple hours, not too hot but enough to make sure they're dry. I remember reading it's not a bad idea to do that with used crucibles too if they've been sitting around unused for a while.

    Jeff
     
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  7. It's a good idea to segregate aluminium and copper alloy crucibles: aluminium greatly increases fluidity of brasses and bronzes but can cause porosity in copper alloys. So keep one crucible for aluminium and another for copper alloys. I don't do anything special for my crucibles, just make sure they have never gotten damp or wet (can explode) and use them from new right away.
     
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  8. Petee716

    Petee716 Gold Banner Member

    Go to Legends homepage and select assay supplies, then crucibles. You’ll find them listed there.
    I don’t really know, but I suspect all of the manufacturing processes of the crucible are complete by the time we get them. The initial heating of the crucible may very well be just to assure there’s no moisture present. Again, I don’t know, but being an occasional caster I always give my furnace and crucibles a gentle heating before really putting the nuts to them.

    Pete
     
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  9. FishbonzWV

    FishbonzWV Silver Banner Member

    Treat your crucible kindly and it should last many years. I start with a lazy yellow flame while getting the site setup. After 5 minutes or so, turn on the blower and get a small blue flame. When the walls start turning red, bring up the burner. When done, invert the crucible outside the furnace to cool. The foil skin pulls right out. No flux, no de-gassing.
     
  10. bjf66

    bjf66 Copper

    Hi haven't been on for a while
    crucibles are inert, if they get wet you need to dry them out prior to use, they aren't going to breakdown over time
    If the crucible gets wet, don't heat them with burner furnace, you could turn crucible upside down and mount an iridescent light bulb (small-med crucible 60watt), within a day crucible will be very hot and moisture will be pushed out of porosity form inside to outside
    Then start your normal preheating procedure
    Crucibles generally come ready to use from Vesuvius or Morgan, there are difference between them porosity, density, glazes, structure, therefore some heat up faster than others, others erode slowly at higher temperatures, and the other low costs crucibles will oxidise with lower temp eg alum

    Some crucibles have more porosity and structure than others, eg, Morgan Salamander clay graphite
    Vesuvius clay graphite are denser and have 1/3 of porosity, this means they need to be heated slowly first and will melt quicker as improved heat transfer, these crucibles are slightly more $$$, however they weigh 20% more than Salamander

    Sure you can heat the crucible in electric resistance oven to warm them up, in a electric resistance furnace melting there is not normally in issues with thermal shock.
    Remember the metal will start melting when its reached its eutectic point, so wait for the puddle of molten metal and then proportional keep adding scrap until melt is finished
    The scrap wont melt until the alloy is inside crucible and seeing heat, so charge early
     

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