Porcelaine firing time VS zirconia frame size

[Dali k]

How do you guys calculate your firing programe lenth for porcelaine over zirconia when dealing with bigger zirconia sub-structures? We end up having very long firing programmes, I wonder if its not too much... What are your formulas or ways to calculate the hold and cooling time?



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[Contraluz]

How do you guys calculate your firing programe lenth for porcelaine over zirconia when dealing with bigger zirconia sub-structures? We end up having very long firing programmes, I wonder if its not too much... What are your formulas or ways to calculate the hold and cooling time?

In the 'battle' of pfm vs. zr, the long firing cycles is one of the drawback... I don't think there is a 'formula'. I increase about 10 degrees celsius for bigger frames and add holding time. But slow cooking and long time cooling is equally important!

M

 

[PDC]

My furnace has 2 selectable cooling positions and will hold the crowns at those positions until temps drop back to entry level. Heat rise rates around 40-45C/min. Hold time for 1 minute at top temp.
Yes, it is a long cycle but a necessary one.

 

[Sda36]

My furnace has 2 selectable cooling positions and will hold the crowns at those positions until temps drop back to entry level. Heat rise rates around 40-45C/min. Hold time for 1 minute at top temp.
Yes, it is a long cycle but a necessary one.

I would suggest even a bit longer, 25-30°/min rise, 2 min hold at high temp. Then a Really slow cool to room temp if we're talking the really big bridges.

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