Big Fat Air Bubble

[Stephen Richard]

They are using the paper, and they had an issue before with leveling but I just asked him on the phone and they are sure it's been fixed since then. This is what he fired at for a schedule:

 ramp 325 to 1100
       hold for 25min
 ramp 325 to 1550
       hold for 20min

What glass are you firing? 842C is far too high for anything other than float.

 ramp 600 to 1440
       hold for 5min

What ever is a soak at 781C on the way down for?

 ramp down to 950 (they said infinity 999?)
       hold for 40min
 ramp down 150 to 800
       hold for 10min
 ramp down (shut off, infinity 999)
 

There is no bubble squeeze in that schedule.  It would be around 1200 - 1250F for Bullseye, maybe 1330F for float.

I think you need to get more control over the firing process.  Perhaps you should make enough to fill the kiln so you can determine the firing.

[Anne]

Amber's using Uro and Sys 96 Steve.  What schedule should she have used? Neither she nor I know what you mean by bubble squeeze - we need the schedule!

[Becki]

A bubble squeeze is a slow ramp segment added to your schedule to allow the air between the 2 layers of glass to slowly be pushed out before the glass seals together.  There are varied approaches to a bubble squeeze....some just soak at slumping temperatures, as Stephen obviously does, and some combine a slow ramp up with soaks through the slump temps.  I don't always use a bubble squeeze in my schedule but when I do I  ramp up slowly (50-75dph) between 1050 and 1250, a method I learned from another artist, Barbara Muth. It works well for me.

I'm not sure if I even brought up a bubble squeeze because the piece had already been fired...once the bubbles are there the squeeze will do no good.

[Stephen Richard]

Amber's using Uro and Sys 96 Steve.  What schedule should she have used? Neither she nor I know what you mean by bubble squeeze - we need the schedule!

With sincere respect you do not need a schedule.  You need the information to be able to construct a schedule.  You will see Becki has given the explanation of a bubble squeeze. 

the reason that I say you do not need a schedule is that many think a schedule tells them all they need to know.  Unfortunately, using someone else's schedule can only lead to questions down the line.   It is important to know the princilples rather than the schedule.  the principles can help you to build schedules to fit a variety of circumstances, but schedules alone are suitable for only a single kind of application.

Uroboros and S96 use different temperature points and firing strategies for their products.  If you look at their sites you will find the schedules they recommend for general purposes.

Steve