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When you are using clay shelves (also called Mullite shelves) in your kilns, you are combining a fast heat conductor (clay) with a slow heat conductor (glass). Therefore the firing schedules have to be adjusted accordingly.


If you fire with the smallest size shelf for your project you will have less mass to heat up, saving you energy. More space between the shelf and sides of your kiln can help to minimize the risk of  thermal shocking your shelf, your mold and even your glass. Yes, any clay product can crack due to thermal shock, just like glass.  With mullite shelves you have to remember to lift your shelf off the kiln floor with posts for more even heating. You must coat kiln shelves with separator before firing so glass does not stick.


Further down you will find the firing schedules for firing with fiber boards, like Kaiser Lee Board.


   

Basic Firing Schedules To use with Mullite Shelves and Clay Molds Basic Full Fuse for Clay Shelves Basic Slump Fuse for Clay Molds

Let's assume you are using Wissmach 90 or 96 glass no larger then 12" x 12" and about 2 to 3 layers thick.


First you need to fire your piece flat to a full fuse or the desired effect you like.  Make sure to adjust the target temperature (the highest temperature in the schedule) to your kiln characteristic firing schedule.



   

Now let's assume you want to create a dish with a clay mold. Prepare your clay mold and place your pre-fused blank on top. You might have to adjust the target temperature (1270°F) and or time to the shape of your mold.



Firing glass on Alumina/Silica fiber shelves or molds like Kaiser Lee Board is less critical. Fiber board does not conduct heat and therefor can not thermal shock.  You can use as many pieces of fiber board in your kiln as you want without adding firing time or energy cost.  All you have to consider for your firing schedule in your kiln, when using fiber shelves and molds is the glass size and thickness for your projects.




   

To use with Fiber Shelves and Fiber Molds
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Basic Full Fuse and Slump for Fiber Molds

With molds made form Kaiser Lee Board you can also full fuse and slump many projects in one firing. As long as your pieces won’t stretch the glass more than one inch and you don’t fuse two solid layers and slump at the same time.


We have added some FREE tutorials. For more information please visit Kaiserlee.com



   

Segment

Rate (DPH)*

Temperature

Hold

1

600°F (316°C)

1000°F (538°C)

:10

2

AFAP***

1430°F (777°C)**

:12

3

AFAP***

950°F (510°C)

1:00

4

100°F (38°C)

700°F (371°C)

:01

Segment

Rate (DPH)*

Temperature

Hold

1

300°F (167°C)

1000°F (538°C)

:10

2

600°F (316°C)

desired target temp

:10

3

AFAP

950°F (510°C)

1:00

4

100°F (38°C)

700°F (371°C)

:01

Segment

Rate (DPH)*

Temperature

Hold

1

200°F (94°C)

1270°F (688°C)**

:10

2

AFAP***

950°F (510°C)

1:00

3

100°F (38°C)

700°F (371°C)

:01

Segment

Rate (DPH)*

Temperature

Hold

1

400°F (222°C)

1000°F (538°C)

:10

2

600°F (316°C)

1430°F (777°C)**

:10

3

AFAP***

950°F (510°C)

1:00

4

100°F (38°C)

700°F (371°C)

:01

Previously Fused Projects

This is the firing schedule we use for a previously fused project that needs a second firing for various reasons. Refer to the short list of possible firings and the corresponding target temperature. You also need to add to your annealing time, if your glass gets thicker than the 2 to 3 layers or you can shorten it if your glass is thinner.


   

Firing Type

Target Temperature

Hold

additional Full Fuse

1430°F (777°C)

:15

Deep Drop

1250°F (777°C)

observe

Drape

1190°F (510°C)

observe

about 12” square and 2 to 3 layers thick about 12” square and 2 to 3 layers thick Basic Firing Schedules


* DPH = degrees per hour   -  ** Target temperature - please adjust to your kiln and to your desired effect.    -  ***AFAP = as fast as possible


* DPH = degrees per hour   -  ** Target temperature - please adjust to your kiln and to your desired effect.    -  ***AFAP = as fast as possible

Each project might require a few adjustment to the firing schedule. We will be adding more free tutorials and inspirational glass art ideas. The green link is a FREE Tutorial, while the yellow/pink link is an inspirational picture pdf.