Controlling Zinc burnoff in Brass.

Discussion in 'General foundry chat' started by Haus, Oct 17, 2021.

  1. Haus

    Haus Copper

    So... I came across some brass bits and bobs cheap at an estate sale (lots of smaller plumbing connectors, plus a a piece of ugly wall decor...). Did my first brass melt/casting. As usual, I used the steel baking pan skull mold. It came out nice and polished up nicely.. I'm still learning and in the "learn to melt and make ingots, and very basic casting" phase of things. I've done maybe 3 sand castings so far.. but still...
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    One thing I noticed while doing this... when I would stir of press anything under the surface (feeding additional parts into the crucible as the melt proceeded, then stirring once melted) I would get the little whisps of white smoke and flashes of that whitish-green flame of zinc burning off. Not too worried about the fumes as I have a respirator and was expecting some, but wondering if there are some good tricks to limit now much burns off as I did end up cleaning a lot of gunk off the surface , a good bit of which had that yellow zinc oxide look to it.

    Ideas?
     
  2. metallab

    metallab Silver

    Indeed brass is nasty. Don't overheat it too much, wear a respirator (you already have one), a face mask does not help, and just before pouring out remove the dross and gunk.
     
  3. HT1

    HT1 Gold Banner Member

    as the resident Brass Master

    DONT STIR

    the only reason to "stir" is to assure, additional Copper is melted a better way, is to get to the pouring temp, and turn off the the furnace, and give the heat some time to work on the melt ,

    stirring will break "slag" off from the side of the crucible, it will pop to the top, it's heavy with Zinc, so you get additional flare.

    there is no getting around having a zinc flare with brass, love it, or switch to Evendure like all the ARTISTES real metal casters make complete casting that dont need welded, and suck up Zinc to prevent Covid

    Can I get a HOOAHH??


    V/r HT1

    P.S. note a minor touch of sarcasm
     
    savarin and Bldr J like this.
  4. Bldr J

    Bldr J Copper

    HOOAHH!

    I mustn't be an artiste, I'm trying both brass and everdur...
    Thank You HT1 for all your posts, they've helped me a lot.
     
  5. I bought some phosphorous copper shot from a metals processor a month or so back, when I mentioned I was alloying brass he told me they let it sit for a while without stirring to get all the crud to the surface and allow any metal time to melt and alloy. Using an induction furnace would probably set up currents and stir things up too, so they would have to shut off the power and let it sit.
     
  6. HT1

    HT1 Gold Banner Member

    no concerns about stuff not being melted and mixed in an induction furnace, the current moves the metal a lot!, bottom to top, , and it heats more or less center to outside, just a quick dip with a 1/4 inch steel rod (rebar works) to check for any lumps, pour in induction, the zinc flare happens all at once, and once you got it, you are almost ready to pour, maybe a minute or two more, but with no air it's one he11 of a cloud you need real bventillation


    V/r HT1
     

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