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Re: [hobbicast] Re: crucible fills

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  • Ken Retallick
    Lyle, occasionally i visit a non ferrous sand casting foundry and they do use a cover flux with silicon bronze, borax and broken clear glass... dont know
    Message 1 of 15 , Dec 3, 2001
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      Lyle,

      occasionally i visit a non ferrous sand casting foundry and they do use a
      cover flux with silicon bronze, borax and broken clear glass... dont
      know if it is actually needed, but surely couldnt hurt.
      Ken
    • foundryman
      Jim, I agree with Lyle no cover flux is required for silicon bronze . Someone else suggested using clear glass and borax and I agree with that comment. I
      Message 2 of 15 , Dec 4, 2001
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        Jim, I agree with Lyle "no cover flux is required for silicon bronze".
        Someone else suggested using clear glass and borax and I agree with that
        comment. I use the glass cover flux. It is easy to skim off with a piece
        of angle iron and the glass will trap any junk such as bits of sand in the
        melt.

        How to do for a #10 crucible: For medium to hot melts, add a tablespoon of
        cracked glass and a 3 finger pinch of 20 Mule Team borax to the bottom of
        the crucible before melting. For cool melts, add the glass and borax after
        the charge is molten (with you last add of metal--otherwise the glass won't
        have time to melt and migrate to the surface).

        The borax seems to act as a fluidizer for the glass. You want the molten
        glass to be sticky, not crumbly nor too fluid, so vary the amount of borax
        until you find the right amount. You don't need to preheat the angle iron
        skimmer as you want the glass to chill and stick to the skimmer. When cool,
        bang the skimmer against something hard and the glass will shatter off the
        skimmer.

        The choice is yours, you don't have to use a cover for si bronze, but your
        casts will be a bit cleaner if you use the glass cover.

        Darn, this is about the third time I've made this post. Guess I should
        write the book that I've been planning for several years.

        Best, Jerry/foundryman1940/ in Missouri
        Custom Castings by Twaddell
        foundryman@...
        http://members.igateway.net/~jtwad/
      • Lyle
        You need to be careful using glass as a cover flux with silicon bronze because some glass contains a high %tage of lead. Any amount of lead will ruin silicon
        Message 3 of 15 , Dec 4, 2001
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          You need to be careful using glass as a cover flux with silicon
          bronze because some glass contains a high %tage of lead. Any amount
          of lead will ruin silicon bronze. the lead combines with the silicon
          and forms a bunch of crap which will ruin your melt, day and crucible.
          I've seen guys dump sand over the sprue, once mold is poured to
          contain heat and slow the cooling process but never seen glass over
          silicon bronze in the crucible. Ive tried adding glass to homemade
          brass (copper and zinc) and ended up screwing everything up.

          that's what's so cool about this hobby. Everybody does things
          differently and whatever works - I guess.

          LL




          --- In hobbicast@y..., "Ken Retallick" <redline@i...> wrote:
          > Lyle,
          >
          > occasionally i visit a non ferrous sand casting foundry and they do
          use a
          > cover flux with silicon bronze, borax and broken clear glass...
          dont
          > know if it is actually needed, but surely couldnt hurt.
          > Ken
        • Lyle
          Jerry, Silicon bronze is the cleanest stuff I ve ever poured. Don t see how it could be cleaner. What kind of glass do you use. I ve heard that busted up clear
          Message 4 of 15 , Dec 4, 2001
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            Jerry,

            Silicon bronze is the cleanest stuff I've ever poured. Don't see how
            it could be cleaner. What kind of glass do you use. I've heard that
            busted up clear mason jars are best but haven't tried them after my
            misshap a few years ago.

            Does your fluxing build up on the inside of the crucible? This seems
            to be my biggest problem with scrap brass. someof the stuff just
            won't come off, even while the crucible is orange hot.

            Maybe I'm an oddball because I don't use a cover flux on anything.
            But copper alloys (except silicon bronze and there's a debate) will
            lose some alloying elements which need to be replaced.

            One thing for sure, if anyones never poured bronze, start with
            silicon bronze because it's the best, easiest tuff around. Just a
            little harder to machine.

            LL




            --- In hobbicast@y..., "foundryman" <foundryman@i...> wrote:
            > Jim, I agree with Lyle "no cover flux is required for silicon
            bronze".
            > Someone else suggested using clear glass and borax and I agree with
            that
            > comment. I use the glass cover flux. It is easy to skim off with
            a piece
            > of angle iron and the glass will trap any junk such as bits of sand
            in the
            > melt.
            >
            > How to do for a #10 crucible: For medium to hot melts, add a
            tablespoon of
            > cracked glass and a 3 finger pinch of 20 Mule Team borax to the
            bottom of
            > the crucible before melting. For cool melts, add the glass and
            borax after
            > the charge is molten (with you last add of metal--otherwise the
            glass won't
            > have time to melt and migrate to the surface).
            >
            > The borax seems to act as a fluidizer for the glass. You want the
            molten
            > glass to be sticky, not crumbly nor too fluid, so vary the amount
            of borax
            > until you find the right amount. You don't need to preheat the
            angle iron
            > skimmer as you want the glass to chill and stick to the skimmer.
            When cool,
            > bang the skimmer against something hard and the glass will shatter
            off the
            > skimmer.
            >
            > The choice is yours, you don't have to use a cover for si bronze,
            but your
            > casts will be a bit cleaner if you use the glass cover.
            >
            > Darn, this is about the third time I've made this post. Guess I
            should
            > write the book that I've been planning for several years.
            >
            > Best, Jerry/foundryman1940/ in Missouri
            > Custom Castings by Twaddell
            > foundryman@i...
            > http://members.igateway.net/~jtwad/
          • foundryman
            Lyle, I just finished sculpting a belt buckle pattern in the shape of a leaping panther. I ll use a glass cover flux to prevent/minimize inclusions on it s
            Message 5 of 15 , Dec 5, 2001
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              Lyle, I just finished sculpting a belt buckle pattern in the shape of a
              leaping panther. I'll use a glass cover flux to prevent/minimize inclusions
              on it's casting in silicon bronze. You do buckles--try the glass. I don't
              bother with the glass cover when casting utility items.

              Use clear glass! Colored glass gets it's color from metal. Brown beer
              bottles contain iron. I use clear Mayo bottles etc. Just put the bottles
              in a bucket and drop an ingot on them several times.

              The bit of borax won't build up inside your crucible when using the
              glass/borax cover for silicon bronze. In fact the crucible wall will
              continue to thin as you make more and more melts just like it thins without
              the glass. When the wall thickness gets thin enough that I start to worry,
              I give the crucible a high heat while empty, give a good scrape and start
              using it for yellow and red brass.

              I don't use a flux for yellow or red brass as the zinc oxide forms a
              sufficient cover. I have tried so called fluxes to prevent the crud
              building up in yell and red brass crucibles, but haven't found a flux that
              worked. When the crud builds up too much, I try chipping it out of a cold
              crucible. Sometimes this works and sometimes I break the crucible.

              I agree with you regarding silicon bronze. It is a beautiful, easy to cast
              alloy, but hard to machine and slow to polish. Unfortunately, many of my
              customers want yellow brass for their reproductions.


              Best, Jerry/foundryman1940/ in Missouri
              Custom Castings by Twaddell
              foundryman@...
              http://members.igateway.net/~jtwad/
            • foundryman
              Lyle, Just read your E regarding lead in glass vs. silicon bronze. Yes, a leaded glass will really mess up silicon bronze. The lead combines with the
              Message 6 of 15 , Dec 5, 2001
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                Lyle, Just read your E regarding lead in glass vs. silicon bronze. Yes, a
                leaded glass will really mess up silicon bronze. The lead combines with the
                silicon and forms more leaded glass. Use glass that food came in (food
                grade). Clear Mayo bottles, clear wine bottles, etc.

                Best, Jerry/foundryman1940/ in Missouri
                Custom Castings by Twaddell
                foundryman@...
                http://members.igateway.net/~jtwad/
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