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Re: [hobbicast] Getting slag out of a crucible

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  • Eric Poulsen
    ... WRT #1 and #2: A thick steel (1/8 or 3/16 or greater) crucible will last. Be sure to check it for pits and thin spots before every pour. Coat it with
    Message 1 of 12 , Oct 3, 2006
      >
      > Here is my 2¢:
      >
      > 1. Consider the propane bottle for temporary use only - it is very
      > thin and will fail after a VERY short time - possibly pouring molten
      > metal all over you.
      >
      > 2. Buy a graphite crucible (the size you are talking about go for $10-
      > $30 on ebay).
      >

      WRT #1 and #2:

      A thick steel (1/8 or 3/16 or greater) crucible will last. Be sure to
      check it for pits and thin spots before every pour. Coat it with kiln
      wash or other refractory material and bake it to dry it.

      Clay graphite crucibles are generally unavailable on Ebay, except for
      the occasional odd sale. The source for these items (LA Graphite) no
      longer sells them at all. As near as I can tell, they are out of business.

      Legend mining sells inexpensive clay-graphite crucibles, but they are
      rated oddly. Typically a #10 crucible means "10 pounds of aluminum".
      Their #10 is "10 _kilos_ of _copper_." Multiply by 0.66 to get the
      "normal" size, in pounds of aluminum. This figure comes from two
      things: 1) Aluminum has a density of .3 that of copper, and 2) A kilo is
      2.2 pounds. 2.2 * .3 = .66.

      In other words, a #16 Legend crucible is equivalent to a #10.5 aluminum
      crucible.

      http://www.lmine.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=LMS&Product_Code=17368
      http://www.lmine.com/minesupply/m58.htm

      I have never bought anything from Legend, nor do I know anything WRT the
      quality of their products. I do not work for them, and am in no way
      affiliated with them. I simply found them on Google.
      > 3. Your metal sounds like it should be a few hundred degrees hotter
      > than you have it.
      >
      > 4. It is usually best to melt, clean on the the slag, and then bring
      > the temperature back up.
      >
      > 5. It is best to cast ingots, and then remelt only ingots for your
      > work - it makes a huge difference in quality.
      >
      >
      > Jeshua Lacock, Owner
      > <http://OpenOSX.com>
      > phone: 877.240.1364
      >
      >
      >
      >
      >
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      > this list does not accept attachments.
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    • Jack
      Go to the supermarket and get some borax. Drop a couple of teaspoonsful into your pot and stir before you pour...this helps to reduce the amount of slag and
      Message 2 of 12 , Oct 3, 2006
        Go to the supermarket and get some borax. Drop a couple of
        teaspoonsful into your pot and stir before you pour...this helps to
        reduce the amount of slag and cause it to float to the surface. Scoop
        of as much slag as possible with a stainless steel serving spoon.
        Then pour. You'll always have a lot of slag from melting scrap (I
        find about 50% slag when melting drink cans).

        Since it always takes some time to get your furnace up to heat you
        should plan on doing multiple melts each session - second and third
        melts are MUCH quicker that the first. Maybe a couple for turning
        scrap into ingots and then one for your casting project.

        Using wood, you'll have difficulty getting a good pour temperature.
        Use charcoal instead (start the fire with barbeque firelighters).

        Your crucible is unlikely to fail catastophically, but do inspect
        before each melt. I use a piece of 4 inch diameter x 3/16 thick steel
        pipe with a 3/16 thick base welded on. A couple of lugs welded on
        near the top allow me to pick it out of the furnace with a crucible
        lifting tool made for the job. That crucible is still going strong
        after about 40-50 melts. My furnace is gas-fired with propane.

        As to slag in the crucible, As soon as I have finished a pour, I up-
        end the crucible and bang it onto a concrete slab several times to
        remove any remaining slag while it is still hot. It doesn't get it
        all but it keeps it to a minimum. Anything remaining will not cause
        big problems in your next melt. I understand that erosion of the
        crucible can be reduced by using kiln wash renewed before each
        melt...I have yet to try it.
        Jack




        --- In hobbicast@yahoogroups.com, "wturchyn" <wturchyn@...> wrote:
        >
        > I've only done three melts so far, so I'm not a seasoned caster yet.
        > For a crucible, I am using an (empty) propane cylinder with the top
        > cut off. This is one of the camping-size cylinders, about 4" in
        diameter.
        >
        > Yesterday, I was melting down some aluminum lawn chair tubing. For
        > heat I was just using scrap wood, and running a blower into the
        > tuyere. As I expected, there was quite a lot of slag. In fact, it's
        > possible that half of the aluminum was slag. (?) I did scoop some of
        > it off, but left quite a bit behind. I pulled the crucible from the
        > furnace, and tilted it into my muffin-tin forms. I got 4 nice
        ingots,
        > and then the remaining material (mostly slag, I think?) just froze
        in
        > the crucible.
        >
        > So now what do I do? I guess I could fire up the furnace again,
        > soften up whatever slag+aluminum is in the crucible, then scoop it
        out
        > a bit at a time. The crucible doesn't have any draft, so I can't
        just
        > turn it upside down and knock the frozen slag out.
        >
        > I guess it may be possible that what's left in the crucible isn't
        just
        > slag, and it just wasn't hot enough when I poured -- froze too
        > quickly. For people who have crucibles made from welded pipe, I'm
        > guessing the crucible has a lot of thermal mass (more than a steel
        > propane cylinder), so maybe the melted metal doesn't freeze as
        quickly
        > in the crucible?
        >
        > Anyway, seeking advice from those who have poured before me.
        >
      • Stone Tool
        Eric: Here s a suggestion I thought of after reading your post....... Take a large spike (nail) or some steel wire, and put it into the crucible at the end of
        Message 3 of 12 , Oct 3, 2006
          Eric:
          Here's a suggestion I thought of after reading your post....... Take a
          large spike (nail) or some steel wire, and put it into the crucible at
          the end of the pour..... let it freeze in, and pull the left over junk
          out by the wire or nail.

          H.W.

          Eric Poulsen wrote:
          > I have the pipe style crucible -- I have the same problem. Often it is
          > thin enough I can just pull it out with pliers after everything has cooled.
          >
          > wturchyn wrote:
          >> I've only done three melts so far, so I'm not a seasoned caster yet.
          >> For a crucible, I am using an (empty) propane cylinder with the top
          >> cut off. This is one of the camping-size cylinders, about 4" in diameter.
          >>
          >> Yesterday, I was melting down some aluminum lawn chair tubing. For
          >> heat I was just using scrap wood, and running a blower into the
          >> tuyere. As I expected, there was quite a lot of slag. In fact, it's
          >> possible that half of the aluminum was slag. (?) I did scoop some of
          >> it off, but left quite a bit behind. I pulled the crucible from the
          >> furnace, and tilted it into my muffin-tin forms. I got 4 nice ingots,
          >> and then the remaining material (mostly slag, I think?) just froze in
          >> the crucible.
          >>
          >> So now what do I do? I guess I could fire up the furnace again,
          >> soften up whatever slag+aluminum is in the crucible, then scoop it out
          >> a bit at a time. The crucible doesn't have any draft, so I can't just
          >> turn it upside down and knock the frozen slag out.
          >>
          >> I guess it may be possible that what's left in the crucible isn't just
          >> slag, and it just wasn't hot enough when I poured -- froze too
          >> quickly. For people who have crucibles made from welded pipe, I'm
          >> guessing the crucible has a lot of thermal mass (more than a steel
          >> propane cylinder), so maybe the melted metal doesn't freeze as quickly
          >> in the crucible?
          >>
          >> Anyway, seeking advice from those who have poured before me.
          >>
          >>
          >>
          >>
          >>
          >>
          >>
          >>
          >> For discussion of Metal Casting and related issues
          >> this list does not accept attachments.
          >>
          >> Files area and list services are at:
          >> http://groups.yahoo.com/group/hobbicast
          >>
          >> For additional files and photos and off topic discussions
          >> check out these two affiliated sites:
          >> http://groups.yahoo.com/group/sandcrabs
          >> http://groups.yahoo.com/group/Hobbicast1
          >>
          >> Please visit our sponsor: Budget Casting Supply
          >> http://budgetcastingsupply.com/
          >>
          >> List Owner:
          >> owly@...
          >>
          >>
          >> Yahoo! Groups Links
          >>
          >>
          >>
          >>
          >>
          >>
          >>
          >>
          >>
          >>
          >>
          >
          >
          >
          > For discussion of Metal Casting and related issues
          > this list does not accept attachments.
          >
          > Files area and list services are at:
          > http://groups.yahoo.com/group/hobbicast
          >
          > For additional files and photos and off topic discussions
          > check out these two affiliated sites:
          > http://groups.yahoo.com/group/sandcrabs
          > http://groups.yahoo.com/group/Hobbicast1
          >
          > Please visit our sponsor: Budget Casting Supply
          > http://budgetcastingsupply.com/
          >
          > List Owner:
          > owly@...
          >
          >
          > Yahoo! Groups Links
          >
          >
          >
          >
          >
          >
          >
          >
          >
        • Eric Poulsen
          ... That s not a bad idea! But, since the walls of my crucible are straight, anything that would require any force to get out won t come out easily anyway.
          Message 4 of 12 , Oct 3, 2006
            Stone Tool wrote:
            > Eric:
            > Here's a suggestion I thought of after reading your post....... Take a
            > large spike (nail) or some steel wire, and put it into the crucible at
            > the end of the pour..... let it freeze in, and pull the left over junk
            > out by the wire or nail.
            >
            > H.W.
            >

            That's not a bad idea!

            But, since the walls of my crucible are straight, anything that would
            require any force to get out won't come out easily anyway. Today I
            pulled slag out of the bottom with my hand. It's layers of crap and AL,
            so it folds easily enough.
          • Eric Poulsen
            ... I didn t think anyone actually melted those cans on a hobby basis because of ... all the slag. ... I haven t been keeping up on my kiln wash coatings, but
            Message 5 of 12 , Oct 3, 2006
              Jack wrote:
              > Go to the supermarket and get some borax. Drop a couple of
              > teaspoonsful into your pot and stir before you pour...this helps to
              > reduce the amount of slag and cause it to float to the surface. Scoop
              > of as much slag as possible with a stainless steel serving spoon.
              > Then pour. You'll always have a lot of slag from melting scrap (I
              > find about 50% slag when melting drink cans).
              >
              I didn't think anyone actually melted those cans on a hobby basis
              because of ... all the slag.
              > big problems in your next melt. I understand that erosion of the
              > crucible can be reduced by using kiln wash renewed before each
              > melt...I have yet to try it.
              >
              I haven't been keeping up on my kiln wash coatings, but it really does
              work. With a good coat, the interior of the crucible remained coated
              through the first melt/pour, and the AL didn't come into contact with
              the steel. The coat does chip off, though, as the crucible cools.

              It's really important to bake on the kiln wash immediately after
              application, as it is water-based, and will rust a plain steel crucible.
              > Jack
              >
            • Jack
              Melting drink cans makes for good exercise. At around maybe 25 cans to the pound and my crucible holds about 4 pounds, I ve got to crush about 100 or so cans
              Message 6 of 12 , Oct 4, 2006
                Melting drink cans makes for good exercise. At around maybe 25 cans
                to the pound and my crucible holds about 4 pounds, I've got to crush
                about 100 or so cans to a size that will fit in the crucible. The
                smaller the better so as to fit as many as possible. Then as they
                start melting, I drop more through the top vent into the crucible
                until I have a full charge. Borax, stir, skim, and I then pour a
                buncha half pound ingots: exercise and sauna all at the same time!
                Jack





                --- In hobbicast@yahoogroups.com, Eric Poulsen <eric@...> wrote:
                >
                > Jack wrote:
                > > Go to the supermarket and get some borax. Drop a couple of
                > > teaspoonsful into your pot and stir before you pour...this helps
                to
                > > reduce the amount of slag and cause it to float to the surface.
                Scoop
                > > of as much slag as possible with a stainless steel serving spoon.
                > > Then pour. You'll always have a lot of slag from melting scrap (I
                > > find about 50% slag when melting drink cans).
                > >
                > I didn't think anyone actually melted those cans on a hobby basis
                > because of ... all the slag.
                > > big problems in your next melt. I understand that erosion of the
                > > crucible can be reduced by using kiln wash renewed before each
                > > melt...I have yet to try it.
                > >
                > I haven't been keeping up on my kiln wash coatings, but it really
                does
                > work. With a good coat, the interior of the crucible remained
                coated
                > through the first melt/pour, and the AL didn't come into contact
                with
                > the steel. The coat does chip off, though, as the crucible cools.
                >
                > It's really important to bake on the kiln wash immediately after
                > application, as it is water-based, and will rust a plain steel
                crucible.
                > > Jack
                > >
                >
              • alaska_woodwright_and_blacksmith
                ... for ... no ... business. ... The Graphite Store, www.graphitestore.com, regularly has crucibles on eBay. That is where I have bought my last two. I also
                Message 7 of 12 , Oct 6, 2006
                  > Clay graphite crucibles are generally unavailable on Ebay, except
                  for
                  > the occasional odd sale. The source for these items (LA Graphite)
                  no
                  > longer sells them at all. As near as I can tell, they are out of
                  business.
                  >
                  The Graphite Store, www.graphitestore.com, regularly has crucibles on
                  eBay. That is where I have bought my last two. I also haven't done
                  business with Legend but have had friends who report both glowing and
                  horrible experiences. You pays your price...and youse takes your
                  chances, I guess.

                  JTL
                • David Patterson
                  http://budgetcastingsupply.com/Price_Sheet.html#Crucibles I bought mine here. haven t had a problem, just temper them as instructed. a good crucible can fail
                  Message 8 of 12 , Oct 6, 2006
                    http://budgetcastingsupply.com/Price_Sheet.html#Crucibles

                    I bought mine here. haven't had a problem, just temper them as instructed. a good crucible can fail if not proprerly handeled.


                    alaska_woodwright_and_blacksmith <alaska_woodwright_and_blacksmith@...> wrote:
                    > Clay graphite crucibles are generally unavailable on Ebay, except
                    for
                    > the occasional odd sale. The source for these items (LA Graphite)
                    no
                    > longer sells them at all. As near as I can tell, they are out of
                    business.
                    >
                    The Graphite Store, www.graphitestore.com, regularly has crucibles on
                    eBay. That is where I have bought my last two. I also haven't done
                    business with Legend but have had friends who report both glowing and
                    horrible experiences. You pays your price...and youse takes your
                    chances, I guess.

                    JTL






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                  • Eric Poulsen
                    Last two times I checked Ebay, I found exactly zero clay-graphite crucibles on Ebay. When there were crucibles, it was from la graphite. Only clay-graphite
                    Message 9 of 12 , Oct 6, 2006
                      Last two times I checked Ebay, I found exactly zero clay-graphite
                      crucibles on Ebay. When there were crucibles, it was from la graphite.

                      Only clay-graphite crucibles that I can find on the graphitestore.com
                      website begin at #25, which is a bit large.

                      I can't speak for the quality of Legend crucibles.

                      alaska_woodwright_and_blacksmith wrote:
                      >> Clay graphite crucibles are generally unavailable on Ebay, except
                      >>
                      > for
                      >
                      >> the occasional odd sale. The source for these items (LA Graphite)
                      >>
                      > no
                      >
                      >> longer sells them at all. As near as I can tell, they are out of
                      >>
                      > business.
                      >
                      > The Graphite Store, www.graphitestore.com, regularly has crucibles on
                      > eBay. That is where I have bought my last two. I also haven't done
                      > business with Legend but have had friends who report both glowing and
                      > horrible experiences. You pays your price...and youse takes your
                      > chances, I guess.
                      >
                      > JTL
                      >
                      >
                      >
                      >
                      >
                      >
                      >
                      > For discussion of Metal Casting and related issues
                      > this list does not accept attachments.
                      >
                      > Files area and list services are at:
                      > http://groups.yahoo.com/group/hobbicast
                      >
                      > For additional files and photos and off topic discussions
                      > check out these two affiliated sites:
                      > http://groups.yahoo.com/group/sandcrabs
                      > http://groups.yahoo.com/group/Hobbicast1
                      >
                      > Please visit our sponsor: Budget Casting Supply
                      > http://budgetcastingsupply.com/
                      >
                      > List Owner:
                      > owly@...
                      >
                      >
                      > Yahoo! Groups Links
                      >
                      >
                      >
                      >
                      >
                      >
                      >
                      >
                      >
                      >
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