Question on Glazing Zirconium.

Getoothachopper

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Coming from a traditional background of porc fused to metal ,I have ideas of heating & cooling zirc which are probably wrong . So my question ,,,,,,when glazing monolithic zirc (singles) in the 750/850c range. Do you need to slow cool or is it okay to have the muffle drop open once the glaze hold time is done ?,,,,,,I have always slow cooled everything but I have a glazing furnace I would like to use that has no slow cool feature . Thanks in advance for any replies.
 
sidesh0wb0b

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Coming from a traditional background of porc fused to metal ,I have ideas of heating & cooling zirc which are probably wrong . So my question ,,,,,,when glazing monolithic zirc (singles) in the 750/850c range. Do you need to slow cool or is it okay to have the muffle drop open once the glaze hold time is done ?,,,,,,I have always slow cooled everything but I have a glazing furnace I would like to use that has no slow cool feature . Thanks in advance for any replies.
small single units i cool for about 2-3min (muffle open time)
larger bridges and PFZ crowns i cool slower.

think of it this way....when you are done sintering at high temp, the oven doesnt just open up and cool off. glazing shouldnt either
 
Andrew Priddy

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ahh.. the question no-one has the answer to. id say Bob has the answer id go with
 
CatamountRob

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Even if the muffle opens quickly, if you leave it sitting there on the platform under the open muffle it’s going to cool fairly slowly.
 
Getoothachopper

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Even if the muffle opens quickly, if you leave it sitting there on the platform under the open muffle it’s going to cool fairly slowly.
Right ! ,,,,this is what i'm thinking . Coming down from (750 in sync paste temp) which isn't really that hot ,we're not talking 1500 sintering temp. Also there are no coefficients of thermal expansion of different materials to worry about. What got me thinking about this was my ivocar programat with preset progs would have the muffle open pretty damn quickly.
 
Getoothachopper

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Nope, red hot and ready.
I'm really starting to think you're right ,,,,esp single units , I'm not talking about quenching them in cold water after all o_O
 
Affinity

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Ive never had an issue dropping them down quickly. Ive never wrapped them in a tissue as I headed out the door because they were too hot to hold... :bag:
 
Getoothachopper

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Ive never had an issue dropping them down quickly. Ive never wrapped them in a tissue as I headed out the door because they were too hot to hold... :bag:
When i'm doing a shade tweak for the Docs next door & the crown is still warm as I walk it next door ,,,,,,,, I always say"Ooooo, still fresh from the oven" 🤣
 
Z

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I can't answer the question about the glazing oven, but I can give you the facts about the zirconia. Zirconia needs to be cooled in a controlled fashion. The optimal cooling rate for singles is 45 degrees per minute to 450 degrees. At that point you can remove from the oven. The cooling for a larger the bulk of zirconia the slower it must be cooled. Full arch restorations I cool at 20-25 degrees a minute to 450. Yes it takes a long time but the failure for the ones not cooled slowly can be a catastrophic failure. I started on the search for answers after a Procera anterior implant split in half on the cooling tray shortly after removing from the oven.
I am not a salesman for Zubler or Ivoclar but if you are doing a lot of zirconia firings you should be using an oven similar to those two. They have a precise cooling program just for the zirconia.

 
rkm rdt

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If you are veneering zirconia then yes, slow the cool.
If the crown is a fcz then let er rip.
 
CatamountRob

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I can't answer the question about the glazing oven, but I can give you the facts about the zirconia. Zirconia needs to be cooled in a controlled fashion. The optimal cooling rate for singles is 45 degrees per minute to 450 degrees. At that point you can remove from the oven. The cooling for a larger the bulk of zirconia the slower it must be cooled. Full arch restorations I cool at 20-25 degrees a minute to 450. Yes it takes a long time but the failure for the ones not cooled slowly can be a catastrophic failure. I started on the search for answers after a Procera anterior implant split in half on the cooling tray shortly after removing from the oven.
I am not a salesman for Zubler or Ivoclar but if you are doing a lot of zirconia firings you should be using an oven similar to those two. They have a precise cooling program just for the zirconia.

He’s not asking about veneered zirconia.
 
Getoothachopper

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So I came up with what I thought was a pretty good Idea ,,,,,, I custom cut an old firing platform (which was a lot taller) & stacked some firing trays, So now when the muffle opens from 750c the crowns are essentially still inside for a slower cool . This is really only going to be used for single monolithic shade tweaks when my other furnaces are in use . This is an old Vita easyglaze that was never even fired up ,,,,,,,it seemed such a shame not to use it in someway . image0.jpeg
 
TheLabGuy

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Be very careful you are not too tall and your crowns hit the top of the muffle (they will stick to the top)...it's a quite the Houdini trick when your table comes down and you wonder where in the heck did my crowns go.
 
rkm rdt

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Be very careful you are not too tall and your crowns hit the top of the muffle (they will stick to the top)...it's a quite the Houdini trick when your table comes down and you wonder where in the heck did my crowns go.
The fun part is grabbing the red crown without touching the sides...while wearing gloves.

1636483036505.jpeg
 
Getoothachopper

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Be very careful you are not too tall and your crowns hit the top of the muffle (they will stick to the top)...it's a quite the Houdini trick when your table comes down and you wonder where in the heck did my crowns go.
It's good , it has one of those old style tall muffles , thx for the tip though . ,,,,,,,,,"I could have entered the 'strangest place you ever found a lost cown' thread that was up here a few weeks ago ,,,,,fused to the thermocouple !"
 
Davor RDT

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All Zirconia firing schedules need a slower heat rise rate and slower cooling/opening , Temperature aside, since it is a poor heat conductor compared to dental alloys and even Alumina . Bigger the unit ( bridges etc. ) slower the rate . Aside from stressing the material by frying it too fast and having cracks develop , surface treatment materials ( stain/glaze or dry or liquid ceramic ) need to attach them selves to zirconia properly as well .
I hope this is helpful
 
TheLabGuy

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It's good , it has one of those old style tall muffles , thx for the tip though . ,,,,,,,,,"I could have entered the 'strangest place you ever found a lost cown' thread that was up here a few weeks ago ,,,,,fused to the thermocouple !"
Been there done that...now a visual, my big ass head trying to fit in the porcelain oven to see where the crown was stuck too!!!
 

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