[Jewelry making - Article 00090] - Re: [Orchid] Casting porosity

[Colin Robertson Jewelry]

========[ Invite a Friend - http://www.ganoksin.com/invite.htm  ]========


    Lee, thanks for the input. A bag of worms indeed! 

    So, we're using a centrifugal casting machine, motor driven, with an
    induction melting coil, and a graphite lined crucible. We're casting
    about 700 grams of metal per tree. Metal temperature I couldn't say,
    doing it by eye, molten and a little beyond. We did try heating it a
    bit more on one cylinder, but had the same results. The flasks we
    tried at 1120, which is the standard temperature we use for brass,
    1040, and 800. No discernible difference. Burn out was 3 hours at
    1380, and using Kerr Flexplast injection wax. This is our standard
    set-up for brass, and has worked well for us with it, for the same
    reason I don't think sprueing is the problem. 

    We tried (This we is my sister and I. My father passed away
    recently, and as he had done a good of the brass casting, and all of
    the silver casting, we're at somewhat of a loss!) one cylinder using
    only the new metal, and got the same result. As far as I know the
    copper is pure, but I tried another using electrical wire, and again
    the same. We have scraped the metal right before releasing it, but
    the slag seems to form again right away. It has a slight greenish
    tinge upon cooling. 

    A guy my sister was talking to who has a foundry in Britain said
    that alloying the metal with the induction set-up might be the
    problem, but that was what my father was doing, though of course
    with the benefit of a lot more experience. Its mainly the outer most
    parts, near the cylinder wall', that are affected, but then there
    are occasional pieces right in the middle of normal looking ones
    which look like torched raisins. 

Thanks again.
Yours,
Hunter


____________________________________________________________________
T h e   O r c h i d   L i s t
Open Electronic Forum for Jewelry Manufacturing Methods and Procedures
____________________________________________________________________
Orchid FAQ:
~ http://www.ganoksin.com/orchid/faq.htm
Orchid Archives:
~ http://www.ganoksin.com/orchid/archive
Orchid Galleries:
~ http://www.ganoksin.com/orchid/gallery.htm
Invite a Friend:
~ http://www.ganoksin.com/invite.htm
____________________________________________________________________
Tips From The Jeweler's Bench - Article Archive
~ http://www.ganoksin.com/borisat/tip_sear.htm
The Jeweler's Selected Bibliography List
~ http://www.ganoksin.com/jewelry-books
Buy Orchid Jewelry:
~ http://www.ganoksin.com/shop
____________________________________________________________________
-Unsubscribe:
-Email: orchid-request AT ganoksin.com Body=unsubscribe subject=blank
____________________________________________________________________