Fused Glass Tack Fuse Schedule (COE 90 & COE 96 Guide)
Firing Suggestions for Precut Glass Shapes (COE 90 & COE 96)
This resource includes a practical fused glass tack fuse schedule for COE 90/96, written for artists who use waterjet-cut precut glass shapes in kilnformed art. Each schedule includes a bubble squeeze to help reduce trapped air (especially when layering precuts over a base) and a proper anneal soak to help prevent stress and cracking. You will find separate schedules for COE 90 (Bullseye) and COE 96 (Oceanside), listed in both Celsius and Fahrenheit. Because every kiln fires differently, use these as a starting point and test small samples before production runs.
Browse precuts by glass system: Shop COE 90 Precuts | Shop COE 96 Precuts
Important notes (read before firing)
- Do not mix COE: Fuse COE 90 with COE 90, and COE 96 with COE 96.
- Build thickness: These schedules are intended for typical 3mm–6mm (1/8"–1/4") builds. Thicker pieces need longer anneal holds and slower cooling.
- Conservative firing is fine: If you prefer slower temperature increases or ramps (for example ~125°C steps), keep the same target temperatures and use slower ramps/longer holds.
- Test & adjust: Kiln size, element placement, shelf type, and thermocouple position can all change results.
COE 90 (Bullseye) – Basic Tack Fuse Schedule (Bubble Squeeze + Anneal)
Anneal temperature (COE 90): 900°F (482°C)
| Segment | Ramp | Target Temp | Hold | Purpose |
|---|---|---|---|---|
| 1 – Initial Heat | 300°F/hr (167°C/hr) | 1100°F (593°C) | 10 min | Even heating through the transition range |
| 2 – Bubble Squeeze | 200°F/hr (111°C/hr) | 1225°F (663°C) | 30–45 min | Reduces trapped air between layers |
| 3 – Tack Fuse | 400°F/hr (222°C/hr) | 1350–1375°F (732–746°C) | 5–10 min | Bonds layers while preserving shape/texture |
| 4 – Anneal Soak | FULL (as fast as kiln allows) | 900°F (482°C) | 60 min | Relieves stress (typical builds up to ~6mm) |
| 5 – Controlled Cool | 100°F/hr (56°C/hr) | 700°F (371°C) | 0 | Controlled cool through the strain range |
| 6 – Cool to Room Temp | 200°F/hr (111°C/hr) | 100°F (38°C) | 0 | Finish cooling |
COE 96 (Oceanside) – Basic Tack Fuse Schedule (Bubble Squeeze + Anneal)
Anneal temperature (COE 96): 950°F (510°C)
| Segment | Ramp | Target Temp | Hold | Purpose |
|---|---|---|---|---|
| 1 – Initial Heat | 300°F/hr (167°C/hr) | 1100°F (593°C) | 10 min | Even heating through the transition range |
| 2 – Bubble Squeeze | 200°F/hr (111°C/hr) | 1225°F (663°C) | 30–45 min | Reduces trapped air between layers |
| 3 – Tack Fuse | 400°F/hr (222°C/hr) | 1350–1375°F (732–746°C) | 5–10 min | Bonds layers while preserving shape/texture |
| 4 – Anneal Soak | FULL (as fast as kiln allows) | 950°F (510°C) | 60 min | Relieves stress (typical builds up to ~6mm) |
| 5 – Controlled Cool | 100°F/hr (56°C/hr) | 800°F (427°C) | 0 | Controlled cool through the strain range |
| 6 – Cool to Room Temp | 200°F/hr (111°C/hr) | 100°F (38°C) | 0 | Finish cooling |
Frequently Asked Questions
Why do COE 90 and COE 96 use different anneal temperatures?
COE 90 and COE 96 are different glass systems with different recommended anneal points. Using the correct anneal temperature and a controlled cool helps reduce internal stress.
What is a bubble squeeze and when should I use it?
A bubble squeeze is a hold in the mid-temperature range that gives trapped air time to escape between layers. It is especially helpful when fusing precuts onto a base, capping a design, or stacking multiple layers. You can also use a think sprinkling of clear powder between layers to aid in your bubble squeeze.
I prefer conservative firing (slow temperature increases). Can I still use these schedules?
Yes. Keep the same target temperatures, but use slower ramps and/or longer holds. Conservative schedules can reduce thermal shock and help accommodate kiln variation.
How do I adjust for thicker pieces?
If your finished piece is thicker than about 6mm (1/4"), increase anneal hold time and slow the cool-down through the strain range. For large or thick work, test small samples and adjust in your kiln.
What tack fuse temperature should I use if I want more texture?
Use a shorter hold and/or the lower end of the tack fuse range. If you want a smoother surface and more rounding, use a slightly longer hold (while watching for loss of detail).
Bibliography / Sources
Manufacturer and primary technical references used to build these guidelines:
- Bullseye Glass Co. Writing Firing Schedules for Fusing & Slumping (PDF). View PDF
- Bullseye Glass Co. TechNotes 4: Heat & Glass. View article
- Oceanside Glass & Tile. Oceanside Compatible Firing Guides. View firing guides
- Oceanside Compatible (System 96). Firing Schedule Examples (PDF). View PDF