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

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  • 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 1 of 24 , Nov 6, 2007
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      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 2 of 24 , Nov 6, 2007
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        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 3 of 24 , Nov 6, 2007
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          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 4 of 24 , Nov 6, 2007
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            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 5 of 24 , Nov 6, 2007
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              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 6 of 24 , Nov 6, 2007
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                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 7 of 24 , Nov 6, 2007
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                  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 8 of 24 , Nov 6, 2007
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                    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 9 of 24 , Nov 6, 2007
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                      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 10 of 24 , Nov 6, 2007
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                        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 11 of 24 , Nov 6, 2007
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                          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 12 of 24 , Nov 6, 2007
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                            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 13 of 24 , Nov 7, 2007
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                              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 14 of 24 , Nov 7, 2007
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                                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 15 of 24 , Nov 7, 2007
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                                  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 16 of 24 , Nov 8, 2007
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                                    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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