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Thread: Delft clay

  1. #11
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    Apr 2012
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    East Sussex
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    What a brilliant set of instructions, pity you didn't have photo's of the pour Ha Ha! very informative I am trying to cast a 3mm thick ring and cannot get it to cast yet. I think you are right lots of air holes and big funnel. Every time I cast the silver freezes before filling the mould, still try again. But brilliant walkthrough.

  2. #12
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    Sep 2010
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    Banbury
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    Oh Vernon - I feel your pain! The operative word I think is DUMP the molten silver not POUR the molten silver! To pour implies steady whereas what you need is speed. The problem I found was that it's kinda counter intuitive to tip the scorifier as fast as you need to. Some how just chucking red hot metal into a mould seems wrong. Try and dump it into the mould as fast as you possibly can. Keeping the heat on the silver as it goes in seems to make a difference.
    Thanks for liking the blog.
    Didi.

  3. #13
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    Apr 2012
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    East Sussex
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    As I work in my conservatory I cannot fit a centrifugal caster in so I am persevering with the clay. Do you think one of the thin circular scorifiers would soak up less heat, maybe?

  4. #14
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    Sep 2010
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    Banbury
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    Hi Vernon.
    Centrifugal caster! ha ha! That would be a pipe dream for me too. I don't know wether the scorifier soaking up the heat is a problem. Mine got so it glowed read as I heated it up. I use the 2" scorifier that Cookies sell, it seems to work ok for me but I do use my seivert torch with a medium burner to heat it. Do you have a big enough torch? It did work better when I built a little kiln with fire blocks to keep the heat in. Melting the silver does seem to take longer than I expected it to though. The silver has to really wobble and slosh around in the bowl before you're ready to pour. Other useful things I found out - If you remelt silver several times it loses it's ability to flow cleanly. Several of the later daisies didn't fill the mould and I think it was the degraded silver rather than technique. Borax powder is essential, not a luxury. Rest the scorifier right on the mould over the funnel before you pour it and then whip it in. Patience is a virtue - or so I'm told!
    Good luck.
    Didi

  5. #15
    Join Date
    Jul 2009
    Location
    Romsey
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    When you're pouring the silver, it's best to have it at what's termed "superheat" - where rather than just being liquid, the molten silver is spinning in the scorifier. Keep the flame on the lip of the scorifier as you're pouring too.
    Centrifugal casters use centripetal acceleration to force metal into the mould, vacuum casters use air pressure, steam casters use steam pressure but all the poor Delft system has to rely upon is the hydrostatic pressure of the molten metal. Hence large casting spouts, fairly chunky sprues and relatively simple moulds...

  6. #16
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    Apr 2012
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    East Sussex
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    That's all great advice. I use the Smiths Little Torch with the melting tip and I am sure that I do not wait long enough for the silver to get hot enough, Impatience! I really should take longer but I want to see the result!

  7. #17
    Join Date
    Jun 2015
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    What advice can anyone give re sourcing Delft clay of reliably good quality at reasonable price? Reputable jewellers' suppliers sell it at prices that seem steep to me for a bit of sand and oil - or am I underestimating what goes into it? A while back I bought a couple of kilos relatively cheap on eBay and did some experimental casting with pewter, but I don't want to risk too much silver if the stuff isn't what it should be... Does anyone make their own?
    Alan

  8. #18
    Join Date
    Jan 2012
    Location
    dear old Blighty - (in deepest Wiltshire)
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    I posted this link before, but it never hurts to repeat I guess.

    Petrobond is a good and economical alternative to Delft. It is reliable and produces great results.
    http://www.mindsetsonline.co.uk/Cata...0-000000000000

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