Is Mizzou not obsolete ?

Discussion in 'Furnaces and their construction' started by metallab, Jan 25, 2022.

  1. metallab

    metallab Silver

    With the advent of modern refractories like Kaowool, which insulate much better, are solid concrete heatsoaking refractories not becoming obsolete ?
    I have an old Mizzou furnace which is now actually inside a 2" Kaowool lining and yet it does not heat up as good as a Kaowool only lining. The concrete soaks up too much heat.

    Or am I doing something wrong ?
     
  2. Petee716

    Petee716 Gold Banner Member

    It’s strength and durability are certainly important factors, especially with the various types of abuse my furnaces take in terms of flame impingement, splashed metal, lifting tools, etc. It would seem that a castable refractory of a reasonable thickness (or thinness) enclosed in koawool would reach a point of saturation and no longer be a source of heat loss.
    So, it might not be wanted or needed for every application, but it still has plenty of applications.

    Pete
     
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  3. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    IMO, dense refractories such as Mizzou are not obsolete and ceramic fiber insulation like Kawool are no more or less "modern" than many other of the other commercial refractory materials. They are different materials with different qualities. The advantage you ascribe to Kawool is more of a hobbyist's perspective. In a commercial setting you would value durability more highly since commercial furnaces are maintained at temperature instead of used for one heat, so the energy to raise the temperature of refractory on the first heat is far less of a factor.

    Best,
    Kelly
     
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  4. Jason

    Jason Gold

    Ya put the two together and you get one hell of a good furnace.
     
  5. Wild Irish

    Wild Irish Copper Banner Member

    Just browsing and ran across this discussion. I just built mine last summer. 20220211_160959 (1).jpg It is an enameled steel washing machine tub lined with a 1" thick layer of a heavy fiber mat used to line boilers (salvaged from work 20 yrs. ago). Inside that is Mizzou lining with a crucible base disk in the bottom surrounded by Mizzou to the wall. It has a commercial cast iron burner tube made for natural induction with propane, but I converted it to natural gas, and it doesn't pull enough air without adding the small fan to help it along. It is slow, taking about an hour to melt about 12 lbs. of aluminum from cold, but I don't have to worry about running out of fuel half way through a melt. Also, judging from the last gas bill for my shop, it doesn't cost much to run, either. The lining has held up through about eight or ten firings and still looks like brand new, with no cracking or deterioration anywhere. Don't mean to hijack the discussion, but thought this might be info. you'd be interested to know. Mike
     
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  6. Smoking Shoe

    Smoking Shoe Copper Banner Member

    Like the idea of using the washer tub! May have to start looking for a stainless one to hoard for the next project.
     
  7. Wild Irish

    Wild Irish Copper Banner Member

    I wanted something bigger than the numerous designs built using 5 gal. buckets, or similar. The tub was given to me by the local appliance repair shop owner who had dozens of them lying around. It will accommodate my largest crucible easily, so will handle any pouring job I'll probably ever do. I welded loops on the sides so it can be picked up with my engine hoist and rolled around to anywhere I want to put it, easily. It was also big enough for a generous layer of insulation around the outside of the refractory so it is almost cool enough to put your bare hand on clear up til almost melting temperature. Mike
     
  8. Bldr J

    Bldr J Copper

    I like the dishwasher dryer blower...kitchen aid?
    I have a similar setup and perfectly happy with the mizzou/2" insulation.
     
  9. Wild Irish

    Wild Irish Copper Banner Member

    -Not sure what blower it is, as it was just a piece of junk I had salvaged somewhere, but now that you mention it, it could be out of a dishwasher :) I used it because everything else I tried had too much air flow. The added bonus is the heat element in it pre-heats the air a little bit. Probably does nothing at all for the firing process, but I'll always think it does anyway :)
     
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  10. Petee716

    Petee716 Gold Banner Member

    I was wondering if the heating element was functional. No telling how much good it really does, but I'll bet it helps!
     
  11. Wild Irish

    Wild Irish Copper Banner Member

    Well, I lied.....just did a melt yesterday, and it took more like close to 2 hours to get up to proper pouring temp. The time I stated previously was for a pour that was not successful because the temperature was too low. Also, I think I melted more aluminum this time.
     
  12. Bldr J

    Bldr J Copper

    It takes me about 1h45 to get to 1200C for a #4 full of Everdur, but the next melts are way quicker, and it's natural gas. I don't think that's too bad, but I think there's some good reason for lightweight/thin refractories...
     
  13. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    WI, do you have a rough estimate of how many lbs of refractory are present in your furnace?

    Best,
    Kelly
     
  14. Rasper

    Rasper Silver

    My small furnace is made of 3 inches of ditch-bank clay and sand, rammed up hard and lined with an inch of Mizzou. I melt a number 8 crucible with 20 lbs of Everdur from cold to pouring temperature in way less than a half-hour using a Lionel Hot Shot burner burning waste motor oil. I have accomplished the same using the Hot Shot burning propane. You have to throw heat to a furnace to melt metal. I have been using this furnace for ten years melting bronze and it has not cracked yet. Mizzou is good stuff.

    Richard
     
  15. Jason

    Jason Gold

    Not at all... I move my kaowool and satanite glass glory hole the other day and stuck my finger right through that sucker. Frankly it kinda pissed me off. I'm glad my furnace is kaowool and mizzou. Tough as nails and will last forever!
     

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