Firing Guide FAHRENHEIT (need Celsius?)
Updated May 2013
Basic Firing Schedule: Guidelines for firing projects up to 3/8-inch thick.
Slumping Schedule: Basic slump guidelines
THICK Firing Schedules: Guidelines for firing THICK projects ranging from 1/2-inch to 2-inches thick
Forming
Chart:		 Forming stages, definitions, and temperatures for firing System 96 products.
Bubble Squeeze: How to modify firing to reduce or eliminate bubbles
Advanced Full Fuse: 8-Segment Schedule with bubble squeeze ranges given



These are some guidelines for kilnforming projects of common thicknesses. Click here for information on firing
thicker projects. These are not strict rules, of course. Times and temperatures may vary with equipment.

BASIC 6-Segment Firing Chart (For projects up to 3/8" thick)
Segment Rate Temp Hold
(°F per Hour) °F (minutes)
1. Heating I: 250 1050 30
Moderate ramp up then hold to allow soft glass to settle. Soak even longer to reduce bubbles.
here is data
2. Heating II: 250 1250 20
Continue heating, with another hold here to equalize temperatures.
here is data
3. Heat to Forming Stage: 300 See Forming Chart Desired Effect
Heat glass to forming temperature. Consult Forming Chart.
here is data
4. Anneal I: 9999 950 60
Fast ramp down then hold to thoroughly equalize temperatures.
here is data      
5. Anneal II: 200 800 10
Slow cool through sensitive zone, then hold to equalize.
here is data
6. Cool Down: 300 100 0
Moderate ramp down to minimize thermal shock.

 

Slumping Chart (For projects up to 3/8" thick)
Segment Rate Temp Hold
(°F per Hour) °F (minutes)
1. Heating I: 250 250 15
Slow ramp up to 250º then hold to equalize temperature of everything in kiln (minimizes thermal shock).
here is data
2. Heating II: 250 1050 30
Moderate ramp to 1050 and hold.
here is data
3. Heat to Forming Stage: 150 See Forming Chart Desired Effect
Heat glass to forming temperature. Consult Forming Chart.
here is data
4. Anneal I: 400 950 60
Moderate ramp down then hold to thoroughly equalize
temperatures.
here is data
5. Anneal II: 200 800 10
Slow cool through sensitive zone, then hold to equalize.
here is data
6. Cool Down: 300 100 0
Moderate ramp down to minimize thermal shock.

 

Forming Chart Definition Forming Temp
Slump Glass softens and slumps to take the shape of a selected form or mold. Note: small molds may need higher temperatures and/or hold times. 1215º-1250º F
Tack Fuse Separate glass layers are fused together with little deformation beyond softening of edges. 1350º- 1370º F
Contour Fuse Separate glass layers are fused together, edges are soft and rounded, project surface retains the degree of dimesion desired by the artist (any degree beyond Tack but not yet Full fused). 1400º-1450º F
Full Fuse Separate glass layers are completely fused into a single uniform layer, top surface is smooth and void of dimension or relief. 1460º-1470º F

 

Bubble Squeeze To Reduce Bubbles Between Glass Layers

To reduce bubbles between glass layers, fire to encourage a very slow relaxing of the layers, “squeezing” air outward to the edges for release. As the fusing chart indicates, we recommend a lengthy hold at about 1050º F, then a slow ramp up to 1250º F. Increase the effectiveness of your “squeeze” by lengthening your Hold in Segment I and slowing your Rate in Segment 2.

Note: nubbles are best avoided in the design stage. Large areas of uninterrupted layering invite them. For example, a 10 x 10-inch sheet atop another 10 x 10-inch sheet leaves no easy avenue of escape for the air between glass layers. Alternately, a 10 x 10-inch sheet topped with four 5 x 5-inch pieces provides seams to vent trapped air. Design to avoid bubbles for the best prevention.

 

Below is our Advanced Full Fuse Firing Schedule with ranges included for a Bubble Squeeze. As with any firing schedule, you will need to adjust the schedule based on your kiln, and the requirements of your particular project.

Advanced 8-Segment FULL FUSE Schedule (For projects up to 3/8" thick)
Segment Rate Temp Hold
(°F per Hour) °F (minutes)
1. Heating I: 250 250 30
Initial heat from room temperature. Holding here allows the glass to fully accept a moderate amount of heat before ramping up.
here is data
2. Heating II: 250 1050 30-60

Moderate ramp past thermal shock danger, then hold to allow softened glass time to relax before edges seal together. (Add more time here if necessary.)
here is data
3. Heating III: 100-250 1250 10-30
Slowing the ramp speed here + lengthening the hold provides more time for bubbles to find an avenue out. Modify this segment even further if necessary.
here is data
4. Heating IV: 250 1370 20
The hold here gives the glass layers time to settle together before rising to the forming temperature.
here is data
5. Heat to Forming Stage: 300 1465 10
Moderate ramp to forming temperature.
here is data
6. Anneal I: 9999 950 60
Fast ramp down then hold to thoroughly equalize temperatures.
       
7. Anneal II: 200 800 10
Slow cool through sensitive zone, then hold to equalize.
       
8. Cool Down: 300 100

0

 
Moderate ramp down to minimize thermal shock.
© 2013 Spectrum Glass Company, Inc. PO Box 646 Woodinville, WA 98072 USA Phone: 425-483-6699 Fax: 425-483-9007 E-mail: Hotglass@System 96.com

All rights reserved. Spectrum, Waterglass, Artíque and System 96 are registered trademarks of Spectrum Glass Company, Inc. Baroque is a trademark of Spectrum Glass Company.