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Getting slag out of a crucible

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  • wturchyn
    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
    Message 1 of 12 , Oct 2, 2006
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      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.
    • Jeshua Lacock
      ... 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
      Message 2 of 12 , Oct 2, 2006
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        On Oct 2, 2006, at 7:20 PM, 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.


        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).

        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
      • Eric Poulsen
        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.
        Message 3 of 12 , Oct 3, 2006
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          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
          >
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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 4 of 12 , Oct 3, 2006
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            >
            > 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
            >
            >
            >
            >
            >
            > 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
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
          • 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 5 of 12 , Oct 3, 2006
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              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 6 of 12 , Oct 3, 2006
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                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 7 of 12 , Oct 3, 2006
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                  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 8 of 12 , Oct 3, 2006
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                    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 9 of 12 , Oct 4, 2006
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                      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 10 of 12 , Oct 6, 2006
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                        > 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 11 of 12 , Oct 6, 2006
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                          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 12 of 12 , Oct 6, 2006
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                            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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