bubbles in ceramic

[Gdentallab]

I'm making an emax press case with impulse ceramic.
I'm having unusual small air bubbles inside the ceramic after bake.
What could be the reason for those bubbles?

 

[2thm8kr]

Check the side of the porcelain bottle, there should be a number called TG with a temperature in centigrade. Make sure during the firing cycle that you have full vacuum before that temp. That's where I would start.

 

[Gdentallab]

Check the side of the porcelain bottle, there should be a number called TG with a temperature in centigrade. Make sure during the firing cycle that you have full vacuum before that temp. That's where I would start.

Well, no TG on my impulse!
But i'm starting full vacuum @ 450 ¤C.
The bubbles are not showing up. They r inside.

 

[Al.]

What do you mean impulse ceramic?

Are you using Emax ceram?
The emax layering porc has a narrow window between being underfired and getting porosity, or being overfired.

My sweet spot is between 1400 F and 1410 F with 1 minute hold time. The high temp is with the copings placed directly on a honey comb tray the low temp on pegs.
My first wash bake is 1410 if I do a 3rd bake I fire at 1400.
With that I get crystal clear on my clears with no internal bubbles or porosity and no rounded edges.

Err on the side of slightly over firing then back the temp down till you find your sweet spot.

 

[Gdentallab]

impulse is the emax ceram.
I'll try to make the temp bit higher, as i'm baking @1382 F.
Never had problems before, till today.

Could it be the liquid i'm using? Distilled water!

 

[Al.]

impulse is the emax ceram.
I'll try to make the temp bit higher, as i'm baking @1382 F.
Never had problems before, till today.

Could it be the liquid i'm using? Distilled water!

Thats is sometimes the nature of furnaces, the temps will change and mabey the furnace needs to be calibrated.

For my regular ceramic furnace (not my pressing furnace) I never calibrate it I let the clearity of my porc tell me if I need to adjust my temps.

With emax ceram being more sensitive the placement on your tray can mean the difference between porosity or clarity.
I always place my crowns on the edge of the honey comb tray and only place the crowns in the middle of the tray on raised metal pegs.
If I dont raise the crowns in the middle and I place them directly on the tray they will be underfired and the ones on the edge will be fired correctly.

1382 is what the manual recommends but I get crowns full of porosity at that temp.
Try 1400. 1400 is on the edge for me 1410 a bit high 1405 is my sweet spot.

 

[sixonice]

I'm making an emax press case with impulse ceramic.
I'm having unusual small air bubbles inside the ceramic after bake.
What could be the reason for those bubbles?

the ceram is underfired, simple as that! if your using a different oven oter than the ivoclar programat series, adjustments (pretty much 100% of the time!) have to be on the higher end of things. your firing at 1382 F at the high temp which is "out of the book" and a good starting point, but immediately raise that high temp to say 1420 or 1425F. keep starting the vacuum at 840F and have the vacuum release always 2 degrees below whatever high temp you find fires out the ceram properly (for example if your new high temp is 1425, vacuum release should be 1423). running a calibration on your porcelain oven wouldn't be a bad idea either! raising your high temp WILL get rid of those tiny bubbles. what you think are bubbles is actually microscopic air pockets within the glass. easy fix!