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.
Surface finish should be 200 (US mesh) grit. Where
feedthroughs will be installed, holes should be drilled 76
to127 microns (.003" to .005") oversize.
that the sealing surfaces are absolutely clean. (see
frit can be applied by dipping, spraying, painting, screen
printing or extrusion.
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.
Vehicle can be obtained commercially from suppliers such as
Ferro and Drakenfeld.
can produce your own vehicle using amyl acetate or denatured
alcohol with about 1.2% nitrocellulose or equivalent added as
an organic binder.
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.
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.
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
Maintain an oxidizing environment in the furnace at all times.
Adhere to all health and safety recommendations from the frit
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