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Re: [hobbicast] a liner for an electric furnace?

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  • rgsparber@aol.com
    In a message dated 11/5/2007 9:36:12 P.M. US Mountain Standard Time, rwenig2@xplornet.com writes Using a crane to lift the crucible sure should reduce any
    Message 1 of 24 , Nov 5, 2007
      In a message dated 11/5/2007 9:36:12 P.M. US Mountain Standard Time,
      rwenig2@... writes


      Using a crane to lift the crucible sure should reduce any chances of
      bumping the sides of the furnace. How large is your furnace and crucible?

      Have you checked the melting temp of glass? I think the glass will melt.

      Rupert,

      The ID of the furnace is 7" and the crucible is a maximum of 6". The chamber
      is 9" tall and the crucible is 8.5" tall. I did a few trial lifts of the
      crucible before deciding that 7" gave enough clearance. But when I started to
      cut the soft brick, it became clear that this surface is very delicate since it
      has all of these 1" deep and 3/8" wide cuts in it.

      I only melt aluminum so should not get above 1500F. I would expect glass
      would still be solid at this temp.

      Rick
      rgsparber@...
      web site: http://rick.sparber.org




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    • Rupert
      ... Hello Rick, I found the MSDS for Pyrex. Pyrex starts to soften
      Message 2 of 24 , Nov 6, 2007
        rgsparber@... wrote:
        >
        > I only melt aluminum so should not get above 1500F. I would expect glass
        > would still be solid at this temp.
        >
        > Rick
        > rgsparber@...
        > web site: http://rick.sparber.org
        >
        >
        Hello Rick,
        I found the MSDS
        <http://catalog2.corning.com/Lifesciences/en-US/TDL/techInfo_abstract.aspx?productid=007740>
        for Pyrex. Pyrex starts to soften at about 700C (1292 F) according to
        the MSDS. I think Aluminum starts to melt at 1100F with a pouring
        temperature between 1350-1450F so that is very close but a Pyrex liner
        may work (barely).

        --
        --
        yvt

        Rupert Wenig
        Camrose, Alberta, Canada.

        email: rwenig2@...

        http://www3.telus.net/public/rwenig/
      • rgsparber@aol.com
        In a message dated 11/6/2007 6:34:30 A.M. US Mountain Standard Time, rwenig2@xplornet.com writes: Pyrex starts to soften at about 700C (1292 F) according to
        Message 3 of 24 , Nov 6, 2007
          In a message dated 11/6/2007 6:34:30 A.M. US Mountain Standard Time,
          rwenig2@... writes:

          Pyrex starts to soften at about 700C (1292 F) according to
          the MSDS. I think Aluminum starts to melt at 1100F with a pouring
          temperature between 1350-1450F so that is very close but a Pyrex liner
          may work (barely).
          ---------------------------------------------------------------
          YVT,

          Wow, I had no idea glass melted at a temperature close to aluminum Oh well,
          so much for a glass cage.

          The best option so far is to build a simple crane to lift straight up.
          Second best is to go with a smaller crucible.

          Thanks,

          Rick
          rgsparber@...
          web site: http://rick.sparber.org




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        • Rupert
          Hello Rick, I didn t say Pyrex melts at 700C. The MSDS says it starts to soften at 700C. I found one article
          Message 4 of 24 , Nov 6, 2007
            Hello Rick,
            I didn't say Pyrex melts at 700C. The MSDS says it starts to soften at
            700C. I found one article
            <http://cat.inist.fr/?aModele=afficheN&cpsidt=17000908> that mentions a
            glass melting temp of 1210 to 1410°C. I also believe there is a
            temperature range which depends on the actual chemical composition.

            Rupert

            rgsparber@... wrote:
            > In a message dated 11/6/2007 6:34:30 A.M. US Mountain Standard Time,
            > rwenig2@... writes:
            >
            > Pyrex starts to soften at about 700C (1292 F) according to
            > the MSDS. I think Aluminum starts to melt at 1100F with a pouring
            > temperature between 1350-1450F so that is very close but a Pyrex liner
            > may work (barely).
            > ---------------------------------------------------------------
            > YVT,
            >
            > Wow, I had no idea glass melted at a temperature close to aluminum Oh well,
            > so much for a glass cage.
            >
            > The best option so far is to build a simple crane to lift straight up.
            > Second best is to go with a smaller crucible.
            >
            > Thanks,
            >
            > Rick
            > rgsparber@...
            > web site: http://rick.sparber.org
            >
            --
            yvt

            Rupert Wenig
            Camrose, Alberta, Canada.

            email: rwenig2@...

            http://www3.telus.net/public/rwenig/
          • rgsparber@aol.com
            In a message dated 11/6/2007 6:50:17 A.M. US Mountain Standard Time, rwenig2@xplornet.com writes: I didn t say Pyrex melts at 700C. ... Rupert, Sorry for the
            Message 5 of 24 , Nov 6, 2007
              In a message dated 11/6/2007 6:50:17 A.M. US Mountain Standard Time,
              rwenig2@... writes:

              I didn't say Pyrex melts at 700C.

              ---------------------------------------------------------------

              Rupert,

              Sorry for the misquote. The bottom line is that using Pyrex is not a good
              option.

              Rick
              rgsparber@...
              web site: http://rick.sparber.org




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            • Jeshua Lacock
              ... I would recommend ITC-100. It will protect your furnace and make it much more reflective = much more efficient. Do a search for ITC-100 in the archives for
              Message 6 of 24 , Nov 6, 2007
                On Nov 5, 2007, at 7:57 PM, rgsparber@... wrote:

                > I would certainly prefer something electrically insulating and
                > thermally
                > conductive that could take up to 2300F plus be ridged like the
                > sheet metal
                > sleeve.


                I would recommend ITC-100.

                It will protect your furnace and make it much more reflective = much
                more efficient. Do a search for ITC-100 in the archives for more
                information.

                It is made out of Zircon and is very hard and very tough compared to
                refractory. Of course it is still a ceramic, so its not like you can
                beat it with a hammer...

                But if it does get chipped, just paint some more on...

                This stuff is amazing - no furnace should be without it. Warning:
                your furnace will be much brighter - don't stare into it without
                saftey glasses like Beryllium lenses or you run the risk of going blind!


                Cheers,

                Jeshua Lacock, Owner
                <http://OpenOSX.com>
                phone: 877.240.1364
              • rgsparber@aol.com
                Jeshua, This is EXACTLY what I was looking for! And the timing is perfect. I have not installed my element yet so should be able to paint the ITC 100 HT down
                Message 7 of 24 , Nov 6, 2007
                  Jeshua,

                  This is EXACTLY what I was looking for! And the timing is perfect. I have
                  not installed my element yet so should be able to paint the ITC 100 HT down in
                  the element groove too. I estimate a total surface area of 0.3 sq feet and a
                  1 pint bottle does 6 to 12 sq feet according to the site. Even with 2 coats I
                  will have plenty left over.

                  Thank you!

                  Rick Sparber
                  rgsparber@...
                  web site: http://rick.sparber.org




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                • Jeshua Lacock
                  ... Thanks Rick, Awesome - glad to be of some help! I am not affiliated with the product - but the improved reflectivity and uniformness was unbelievable in
                  Message 8 of 24 , Nov 6, 2007
                    On Nov 6, 2007, at 7:20 AM, rgsparber@... wrote:

                    > This is EXACTLY what I was looking for! And the timing is perfect.
                    > I have
                    > not installed my element yet so should be able to paint the ITC 100
                    > HT down in
                    > the element groove too. I estimate a total surface area of 0.3 sq
                    > feet and a
                    > 1 pint bottle does 6 to 12 sq feet according to the site. Even with
                    > 2 coats I
                    > will have plenty left over.

                    Thanks Rick,

                    Awesome - glad to be of some help!

                    I am not affiliated with the product - but the improved reflectivity
                    and uniformness was unbelievable in addition to making the refractory
                    much tougher...

                    Which makes for much quicker startups and drastic improvements of
                    efficiency. And I have run my furnace at 2300F to cast iron - no
                    signs of it deteriorating. In fact I have been told by Ron Reil (of
                    the Reil burner) that one jar can last for decades...

                    It is so great you might be tempted to coat on everything - but don't
                    coat your crucible - it will reflect much of the heat!


                    Cheers,

                    Jeshua Lacock, Owner
                    <http://OpenOSX.com>
                    phone: 877.240.1364
                  • rgsparber@aol.com
                    Jeshua, My crucible is steel. If anything, I would want a heat absorbing coating on it. I really hate painting but this is one paint that will be worth my
                    Message 9 of 24 , Nov 6, 2007
                      Jeshua,

                      My crucible is steel. If anything, I would want a heat absorbing coating on
                      it.

                      I really hate painting but this is one "paint" that will be worth my time.
                      From what I read, two coats of the ITC100 may be in order. That will be around
                      0.6 square feet but I will need a rather small brush to get into those
                      slots.

                      Thanks again!

                      Rick
                      rgsparber@...
                      web site: http://rick.sparber.org




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                    • Jeshua Lacock
                      ... Rick, Sure I understand - just wanted to point that some folks go ITC-100 happy! What size crucible are you using? You can pick up small to medium size
                      Message 10 of 24 , Nov 6, 2007
                        On Nov 6, 2007, at 8:43 AM, rgsparber@... wrote:

                        > My crucible is steel. If anything, I would want a heat absorbing
                        > coating on
                        > it.

                        Rick,

                        Sure I understand - just wanted to point that some folks go ITC-100
                        happy!

                        What size crucible are you using? You can pick up small to medium
                        size graphite crucibles for a steal.

                        It might be a good upgrade to order a graphite crucible. Much more
                        transparent to heat (equals less wasted BTUs and quicker melts) - and
                        you would have even less chance of damaging your refractory...

                        > I really hate painting but this is one "paint" that will be worth
                        > my time.
                        > From what I read, two coats of the ITC100 may be in order. That
                        > will be around
                        > 0.6 square feet but I will need a rather small brush to get into those
                        > slots.

                        One other user note - but I don't think it applies to you - make sure
                        the refractory has been fired at least once before coating or you can
                        have chunks of your refractory blown out...


                        Cheers,

                        Jeshua Lacock, Owner
                        <http://OpenOSX.com>
                        phone: 877.240.1364
                      • rgsparber@aol.com
                        In a message dated 11/6/2007 8:58:02 A.M. US Mountain Standard Time, jeshua@OpenOSX.com writes: One other user note - but I don t think it applies to you -
                        Message 11 of 24 , Nov 6, 2007
                          In a message dated 11/6/2007 8:58:02 A.M. US Mountain Standard Time,
                          jeshua@... writes:

                          One other user note - but I don't think it applies to you - make sure
                          the refractory has been fired at least once before coating or you can
                          have chunks of your refractory blown out...

                          ---------------------------------------------------------------
                          Jeshua,

                          For my class of work, steel crucibles have served me well. It is easy to
                          change to a REAL crucible later.

                          At this time I am about 20 hours into the initial drying time of the
                          refractory. It must dry for 24 to 48 hours before I start my "heat-up schedule". I
                          am painting the firebrick and not the refractory so there should be no
                          problem, right? Or do you expect steam to pass through the brick from the backing
                          refractory and push the coating off of the face of the brick?

                          Once I apply power to the heating element, it will not be possible to coat
                          inside the support slot. I would guess that getting this coating on the
                          element would be very bad.

                          Rick
                          rgsparber@...
                          web site: http://rick.sparber.org




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                        • Jeshua Lacock
                          ... Sounds OK - but I am not sure. If the bricks don t contain moisture it shouldn t pose an obvious threat. If there is not an interface to the refractory I
                          Message 12 of 24 , Nov 6, 2007
                            On Nov 6, 2007, at 9:07 AM, rgsparber@... wrote:

                            > For my class of work, steel crucibles have served me well. It is
                            > easy to
                            > change to a REAL crucible later.
                            >
                            > At this time I am about 20 hours into the initial drying time of the
                            > refractory. It must dry for 24 to 48 hours before I start my "heat-
                            > up schedule". I
                            > am painting the firebrick and not the refractory so there should be no
                            > problem, right? Or do you expect steam to pass through the brick
                            > from the backing
                            > refractory and push the coating off of the face of the brick?

                            Sounds OK - but I am not sure. If the bricks don't contain moisture
                            it shouldn't pose an obvious threat. If there is not an interface to
                            the refractory I guess that it would be OK. But I suppose it would be
                            possible for the bricks to adsorb moisture from the environment - you
                            might want to bake the bricks or something first...

                            Question: How do you expect the moisture to escape from the
                            refractory - through cracks in the bricks? I guess I don't have a
                            clear mental image of your setup...

                            > Once I apply power to the heating element, it will not be possible
                            > to coat
                            > inside the support slot. I would guess that getting this coating on
                            > the
                            > element would be very bad.

                            Yes - it would likely eat through or burn it out...

                            Just keep in mind that ITC-100 will seal the surface, so if it has
                            any moisture in there it could get destroyed...


                            Cheers,

                            Jeshua Lacock, Owner
                            <http://OpenOSX.com>
                            phone: 877.240.1364
                          • rgsparber@aol.com
                            Jeshua, The soft bricks have been protected from moisture since I bought them and appear to be chalk dust dry. I have plastic between these bricks and the
                            Message 13 of 24 , Nov 6, 2007
                              Jeshua,

                              The soft bricks have been protected from moisture since I bought them and
                              appear to be chalk dust dry. I have plastic between these bricks and the moist
                              refractory. I'm not real clear how the moisture gets out of the refractory
                              but the plastic should prevent much of it getting into the bricks. The first
                              few steps in the refractory heat-up schedule are many hours below 300F to drive
                              off the water.

                              I have a steel outer skin, then about a 1" layer of refractory. Then I have
                              a layer of Saran Wrap. In from this plastic is my core of soft bricks. I plan
                              to only coat the inner surface of these bricks.

                              By coating the inner face of the soft bricks I will still have the top of
                              the refractory open to the air plus any moisture that does get into the bricks
                              can exit the top which I will not be coating. So I guess as long as I stick
                              with the schedule, there will be plenty of time to slowly drive out the
                              moisture.

                              Rick
                              rgsparber@...
                              web site: http://rick.sparber.org




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                            • Jeshua Lacock
                              ... Hi Rick, Would it be possible to fire everything once, then remove your element, then coat the bricks? It might be better to be safe than sorry. It just
                              Message 14 of 24 , Nov 6, 2007
                                On Nov 6, 2007, at 9:35 AM, rgsparber@... wrote:

                                > The soft bricks have been protected from moisture since I bought
                                > them and
                                > appear to be chalk dust dry. I have plastic between these bricks
                                > and the moist
                                > refractory. I'm not real clear how the moisture gets out of the
                                > refractory
                                > but the plastic should prevent much of it getting into the bricks.
                                > The first
                                > few steps in the refractory heat-up schedule are many hours below
                                > 300F to drive
                                > off the water.
                                >
                                > I have a steel outer skin, then about a 1" layer of refractory.
                                > Then I have
                                > a layer of Saran Wrap. In from this plastic is my core of soft
                                > bricks. I plan
                                > to only coat the inner surface of these bricks.
                                >
                                > By coating the inner face of the soft bricks I will still have the
                                > top of
                                > the refractory open to the air plus any moisture that does get into
                                > the bricks
                                > can exit the top which I will not be coating. So I guess as long as
                                > I stick
                                > with the schedule, there will be plenty of time to slowly drive out
                                > the
                                > moisture.


                                Hi Rick,

                                Would it be possible to fire everything once, then remove your
                                element, then coat the bricks? It might be better to be safe than sorry.

                                It just sounds a little scary to me because the moisture may be
                                wicked up by the dry bricks through capillary action as soon as your
                                saran wrap melts?

                                Also, even though the bricks seem to be dry as a bone, even
                                imperceptible amounts of water could cause a blowout.

                                I honestly don't know for sure - you will have to use your judgement...

                                Enjoy your furnace may it bring you many, many melts.


                                Cheers,

                                Jeshua Lacock, Owner
                                <http://OpenOSX.com>
                                phone: 877.240.1364
                              • rgsparber@aol.com
                                Jeshua, I am afraid to disturb the heating element after bring it up to full heat. I know it will become brittle. So that means I must paint on the ceramic
                                Message 15 of 24 , Nov 6, 2007
                                  Jeshua,

                                  I am afraid to disturb the heating element after bring it up to full heat. I
                                  know it will become brittle. So that means I must paint on the ceramic
                                  before first firing.

                                  I waited 24 hours after packing the refractory and then separated the
                                  furnace into its 3 pieces. Each has air all around it now. I plan to let it dry for
                                  another 24 hours before painting on the ceramic. I live in the Sonoran
                                  desert and the relative humidity is now 12%. So things should dry quickly.

                                  I'll wait another 24 hours and then start the heat-up schedule. In this
                                  schedule they say that if you see any steam, hold at this temperature until it
                                  stops. IIRC, I spend about 5 hours under 200F. If there is any steam, it will
                                  be a longer wait. So I think I'll be OK as long as I go slow. I was thinking
                                  of placing a 60W bulb in the chamber for the last 24 hours but then realized
                                  that my element at min power puts out around 100W and is more distributed.


                                  Rick
                                  rgsparber@...
                                  web site: http://rick.sparber.org




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                                • Lance
                                  What is the source for steal graphite crucibles? I m looking for some to melt Al, brass and bronze. lance +++++ ... [Non-text portions of this message have
                                  Message 16 of 24 , Nov 6, 2007
                                    What is the source for "steal" graphite crucibles?

                                    I'm looking for some to melt Al, brass and bronze.

                                    lance
                                    +++++
                                    On Nov 6, 2007, at 10:57 AM, Jeshua Lacock wrote:
                                    >
                                    >
                                    > What size crucible are you using? You can pick up small to medium
                                    > size graphite crucibles for a steal.
                                    >
                                    > It might be a good upgrade to order a graphite crucible. Much more
                                    > transparent to heat (equals less wasted BTUs and quicker melts) - and
                                    > you would have even less chance of damaging your refractory...
                                    >
                                    > > I really hate painting but this is one "paint" that will be worth
                                    > > my time.
                                    > > From what I read, two coats of the ITC100 may be in order. That
                                    > > will be around
                                    > > 0.6 square feet but I will need a rather small brush to get into
                                    > those
                                    > > slots.
                                    >
                                    > .
                                    >
                                    >



                                    [Non-text portions of this message have been removed]
                                  • Jeshua Lacock
                                    ... Hi Lance, You might have to look around a little - sometimes they are listed on ebay sometimes they are not. The sponsor of this list also has pretty
                                    Message 17 of 24 , Nov 7, 2007
                                      On Nov 6, 2007, at 8:35 PM, Lance wrote:

                                      > What is the source for "steal" graphite crucibles?
                                      >
                                      > I'm looking for some to melt Al, brass and bronze.

                                      Hi Lance,

                                      You might have to look around a little - sometimes they are listed on
                                      ebay sometimes they are not. The sponsor of this list also has pretty
                                      reasonable prices:

                                      <http://budgetcastingsupply.com/Crucibles.php>


                                      I wish LA Graphite didn't go out of business - I bought two 100#
                                      graphite crucibles for only $180 (*with shipping) - since then the
                                      best deal I have seen on this size crucible is $400 each!


                                      Cheers,

                                      Jeshua Lacock, Owner
                                      <http://OpenOSX.com>
                                      phone: 877.240.1364
                                    • C.S.Johnson
                                      Hi Rick, I would not worry too much about the clearance on your steel crucible. My furnace is 6 dia by 7 1/4 deep and my crucible is 5 dia by 6 3/4 high.
                                      Message 18 of 24 , Nov 7, 2007
                                        Hi Rick,
                                        I would not worry too much about the clearance on your steel crucible. My furnace is 6" dia by 7 1/4" deep and my crucible is 5" dia by 6 3/4" high. In addition the pouring lip sticks out a 1/4" and a tilting lug on the bottom sticks out 5/16". I lift the crucible straight up, by means of a 5/16" rod in two holes across the top of the crucible. The rod has an inverted "V" in the center so that the hand held lifting hook will not slide. The rod is held in place with a couple of split pins. When the crucible is clear of the furnace a second hooked rod is used in the bottom tilting lug to tilt the crucible for pouring. If any damage occurs to the soft bricks they are easily repaired with some fire clay or commercial fire cement, usually available from any builders merchant. I have never damaged my furnace by contact with the crucible. My furnace is made from the Gingery recipe of fire clay,sand and grog, it is fairly fragile and some crumbling has taken place over the years just due to heating and cooling. This was easily repaired with a fire cement and grog mix. The furnace has been in use for five years and had over 60 heats. I have used it mainly for aluminium but it has been used twice for bronze using a small ceramic crucible.
                                        Enjoy your casting
                                        Colin


                                        ----- Original Message -----
                                        From: rgsparber@...
                                        To: hobbicast@yahoogroups.com
                                        Sent: Tuesday, November 06, 2007 4:43 AM
                                        Subject: Re: [hobbicast] a liner for an electric furnace?


                                        In a message dated 11/5/2007 9:36:12 P.M. US Mountain Standard Time,
                                        rwenig2@... writes


                                        Using a crane to lift the crucible sure should reduce any chances of
                                        bumping the sides of the furnace. How large is your furnace and crucible?

                                        Have you checked the melting temp of glass? I think the glass will melt.

                                        Rupert,

                                        The ID of the furnace is 7" and the crucible is a maximum of 6". The chamber
                                        is 9" tall and the crucible is 8.5" tall. I did a few trial lifts of the
                                        crucible before deciding that 7" gave enough clearance. But when I started to
                                        cut the soft brick, it became clear that this surface is very delicate since it
                                        has all of these 1" deep and 3/8" wide cuts in it.

                                        I only melt aluminum so should not get above 1500F. I would expect glass
                                        would still be solid at this temp.

                                        Rick
                                        rgsparber@...
                                        web site: http://rick.sparber.org


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                                        [Non-text portions of this message have been removed]
                                      • rgsparber@aol.com
                                        Colin, It does sound like your crucible is almost a twin of mine. I think I ll buy some refractory cement just to keep on hand when I do have those
                                        Message 19 of 24 , Nov 7, 2007
                                          Colin,

                                          It does sound like your crucible is almost a twin of mine. I think I'll buy
                                          some refractory cement just to keep on hand when I do have those inevitable
                                          collisions.

                                          Thanks!

                                          Rick
                                          rgsparber@...
                                          web site: http://rick.sparber.org




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                                        • Ken Wilson
                                          Lance, You can get reasonably priced graphite crucibles in a variety of sizes at Legend, inc. www.Lmine.com They re a geology/assay company. Look under budget
                                          Message 20 of 24 , Nov 8, 2007
                                            Lance,
                                            You can get reasonably priced graphite crucibles in a variety of sizes
                                            at Legend, inc.
                                            www.Lmine.com
                                            They're a geology/assay company.
                                            Look under 'budget graphite crucibles'
                                            -Ken

                                            --- In hobbicast@yahoogroups.com, Lance <gbof@...> wrote:
                                            >
                                            > What is the source for "steal" graphite crucibles?
                                            >
                                            > I'm looking for some to melt Al, brass and bronze.
                                            >
                                            > lance
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