| 1. | Capable of producing hermetic seals on Macor, forsterite and metals such as Sylvania #4, Dumet, 52% nickel alloys, chrome-iron stainless steel, platinum and Sealmet. |
| 2. | Surface finish should be 200 (US mesh) grit. Where feedthroughs will be installed, holes should be drilled 76 to127 microns (.003" to .005") oversize. |
| 3. | Ensure that the sealing surfaces are absolutely clean. (see Cleaning.) |
| 4. | Glass frit can be applied by dipping, spraying, painting, screen printing or extrusion. |
| 5. | Frit should be mixed between 5:1 and 15:1 frit to vehicle depending upon application method. Make only as much slurry as needed to produce a seal. The slurries have a short shelf life. |
| 6. | Vehicle can be obtained commercially from suppliers such as Ferro and Drakenfeld. |
| 7. | You can produce your own vehicle using amyl acetate or denatured alcohol with about 1.2% nitrocellulose or equivalent added as an organic binder. |
| 8. | After applying the frit, it must be thoroughly dried. Oven drying is recommended but heat lamps can also be used. Keep drying temperature below 350°C (660°F). Suggested drying cycle is heat at 200°C (360°F) per hour to 200°C (390°F), hold for 15 minutes and then cool at the same rate. |
| 9. | To fuse the frit to the Macor to improve handling, heat at 150° to 200°C (270° to 360°F) per hour to the softening point of the frit. Hold for 5 to 10 minutes and cool at the same rate. |
| 10. | Sealing cycles will depend upon seal geometry and sizes. A starting point for experimentation is a heating rate of 150° to 300°C (depending upon size) to the sealing temperature and then holding at temperature for the time specified by the frit supplier. |
| 11. | Maintain an oxidizing environment in the furnace at all times. |
| 12. | Adhere to all health and safety recommendations from the frit supplier. |
| 13. | Seals may be of either vitreous or devitrified glass. The devitrified seals are generally mechanically stronger and many can be machined however, they cannot be reworked if the seal leaks. A vitreous seal can be reworked if it leaks or is misaligned. |
